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[v1,00/11] Redo PolarFire SoC's mailbox/clock devicestrees and related code

Message ID 20241002-private-unequal-33cfa6101338@spud (mailing list archive)
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Series Redo PolarFire SoC's mailbox/clock devicestrees and related code | expand

Message

Conor Dooley Oct. 2, 2024, 10:47 a.m. UTC
From: Conor Dooley <conor.dooley@microchip.com>

Yo,

Here's something that I've been mulling over for a while, since I
started to understand how devicetree stuff was "meant" to be done.
There'd been little reason to actually press forward with it, because it
is fairly disruptive. I've finally opted to do it, because a user has
come along with a hwmon driver that needs to access the same register
region as the mailbox and the author is not keen on using the aux bus,
and because I do not want the new pic64gx SoC that's based on PolarFire
SoC to use bindings etc that I know to be incorrect.

Given backwards compatibility needs to be maintained, this patch series
isn't the prettiest thing I have ever written. The reset driver needs to
retain support for the auxiliary bus, which looks a bit mess, but not
much can be done there. The mailbox and clock drivers both have to have
an "old probe" function to handle the old layout. Thankfully in the
clock driver, the Meson clk-regmap support can be used to identically
handle both old and new devicetree formats - but using a regmap in the
mailbox driver was only really possible for the new format, so the code
there is unfortunately a bit of an if/else mess that I'm both not proud
of, nor really sure is worth "improving".

The series should be pretty splitable per subsystem, only the dts change
has some sort of dependency, but I'll not be applying that till
everything else is in Linus' tree, so that's not a big deal.

I've got all the Meson clock folks on CC, given I am moving their
clk-regmap implementation to common code. There were one or two things I
didn't really like about the implementation, but it is better than the
Qualcomm one IMO and creating a third copy of clk-regmap is certainly
not an improvement on having two copies!

I don't really want this stuff in stable, hence a lack of cc: stable
anywhere here, since what's currently in the tree works fine for the
currently supported hardware.

AFAIK, the only other project affected here is U-Boot - I've got some
WIP work that I need to rebase and send for it before the dts patches
here will be applied:
https://github.com/ConchuOD/u-boot/commits/syscon-clocks/

I previously submitted this as an RFC, only to Lee and the dt list, in
order to get some feedback on the syscon/mfd bindings:
https://lore.kernel.org/all/20240815-shindig-bunny-fd42792d638a@spud/
I'm not really going to bother with a proper changelog, since that was
submitted with lots of WIP code to get answers to some questions. The
main change was "removing" some of the child nodes of the syscons.

Cheers,
Conor.

CC: Conor Dooley <conor.dooley@microchip.com>
CC: Daire McNamara <daire.mcnamara@microchip.com>
CC: pierre-henry.moussay@microchip.com
CC: valentina.fernandezalanis@microchip.com
CC: Michael Turquette <mturquette@baylibre.com>
CC: Stephen Boyd <sboyd@kernel.org>
CC: Rob Herring <robh@kernel.org>
CC: Krzysztof Kozlowski <krzk+dt@kernel.org>
CC: Jassi Brar <jassisinghbrar@gmail.com>
CC: Lee Jones <lee@kernel.org>
CC: Paul Walmsley <paul.walmsley@sifive.com>
CC: Palmer Dabbelt <palmer@dabbelt.com>
CC: Albert Ou <aou@eecs.berkeley.edu>
CC: Neil Armstrong <neil.armstrong@linaro.org>
CC: Jerome Brunet <jbrunet@baylibre.com>
CC: Kevin Hilman <khilman@baylibre.com>
CC: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
CC: Philipp Zabel <p.zabel@pengutronix.de>
CC: linux-riscv@lists.infradead.org
CC: linux-clk@vger.kernel.org
CC: devicetree@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: linux-amlogic@lists.infradead.org
CC: linux-arm-kernel@lists.infradead.org

Conor Dooley (11):
  dt-bindings: mailbox: mpfs: fix reg properties
  mailbox: mpfs: support new, syscon based, devicetree configuration
  dt-bindings: mfd: syscon document the non simple-mfd syscon on
    PolarFire SoC
  dt-bindings: soc: microchip: document the two simple-mfd syscons on
    PolarFire SoC
  soc: microchip: add mfd drivers for two syscon regions on PolarFire
    SoC
  reset: mpfs: add non-auxiliary bus probing
  dt-bindings: clk: microchip: mpfs: remove first reg region
  clk: move meson clk-regmap implementation to common code
  clk: microchip: mpfs: use regmap clock types
  riscv: dts: microchip: fix mailbox description
  riscv: dts: microchip: convert clock and reset to use syscon

 .../bindings/clock/microchip,mpfs-clkcfg.yaml |  36 +++---
 .../mailbox/microchip,mpfs-mailbox.yaml       |  13 +-
 .../devicetree/bindings/mfd/syscon.yaml       |   2 +
 .../microchip/microchip,mpfs-control-scb.yaml |  44 +++++++
 .../microchip,mpfs-mss-top-sysreg.yaml        |  54 +++++++++
 arch/riscv/boot/dts/microchip/mpfs.dtsi       |  34 ++++--
 drivers/clk/Kconfig                           |   4 +
 drivers/clk/Makefile                          |   1 +
 drivers/clk/{meson => }/clk-regmap.c          |   2 +-
 drivers/clk/meson/Kconfig                     |  46 ++++---
 drivers/clk/meson/Makefile                    |   1 -
 drivers/clk/meson/a1-peripherals.c            |   2 +-
 drivers/clk/meson/a1-pll.c                    |   2 +-
 drivers/clk/meson/axg-aoclk.c                 |   2 +-
 drivers/clk/meson/axg-audio.c                 |   2 +-
 drivers/clk/meson/axg.c                       |   2 +-
 drivers/clk/meson/c3-peripherals.c            |   2 +-
 drivers/clk/meson/c3-pll.c                    |   2 +-
 drivers/clk/meson/clk-cpu-dyndiv.c            |   2 +-
 drivers/clk/meson/clk-dualdiv.c               |   2 +-
 drivers/clk/meson/clk-mpll.c                  |   2 +-
 drivers/clk/meson/clk-phase.c                 |   2 +-
 drivers/clk/meson/clk-pll.c                   |   2 +-
 drivers/clk/meson/g12a-aoclk.c                |   2 +-
 drivers/clk/meson/g12a.c                      |   2 +-
 drivers/clk/meson/gxbb-aoclk.c                |   2 +-
 drivers/clk/meson/gxbb.c                      |   2 +-
 drivers/clk/meson/meson-aoclk.h               |   2 +-
 drivers/clk/meson/meson-eeclk.c               |   2 +-
 drivers/clk/meson/meson-eeclk.h               |   2 +-
 drivers/clk/meson/meson8-ddr.c                |   2 +-
 drivers/clk/meson/meson8b.c                   |   2 +-
 drivers/clk/meson/s4-peripherals.c            |   2 +-
 drivers/clk/meson/s4-pll.c                    |   2 +-
 drivers/clk/meson/sclk-div.c                  |   2 +-
 drivers/clk/meson/vclk.h                      |   2 +-
 drivers/clk/meson/vid-pll-div.c               |   2 +-
 drivers/clk/microchip/Kconfig                 |   3 +
 drivers/clk/microchip/clk-mpfs.c              | 114 +++++++++++++-----
 drivers/mailbox/Kconfig                       |   1 +
 drivers/mailbox/mailbox-mpfs.c                |  87 ++++++++++---
 drivers/reset/reset-mpfs.c                    |  83 +++++++++++--
 drivers/soc/microchip/Kconfig                 |  13 ++
 drivers/soc/microchip/Makefile                |   1 +
 drivers/soc/microchip/mpfs-control-scb.c      |  45 +++++++
 drivers/soc/microchip/mpfs-mss-top-sysreg.c   |  48 ++++++++
 .../meson => include/linux/clk}/clk-regmap.h  |   0
 47 files changed, 541 insertions(+), 143 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-control-scb.yaml
 create mode 100644 Documentation/devicetree/bindings/soc/microchip/microchip,mpfs-mss-top-sysreg.yaml
 rename drivers/clk/{meson => }/clk-regmap.c (99%)
 create mode 100644 drivers/soc/microchip/mpfs-control-scb.c
 create mode 100644 drivers/soc/microchip/mpfs-mss-top-sysreg.c
 rename {drivers/clk/meson => include/linux/clk}/clk-regmap.h (100%)

Comments

Neil Armstrong Oct. 2, 2024, 11:20 a.m. UTC | #1
On 02/10/2024 12:48, Conor Dooley wrote:
> From: Conor Dooley <conor.dooley@microchip.com>
> 
> I like this one better than qualcomms and wish to use it for the
> PolarFire SoC clock drivers.
> 
> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> ---
>   drivers/clk/Kconfig                           |  4 ++
>   drivers/clk/Makefile                          |  1 +
>   drivers/clk/{meson => }/clk-regmap.c          |  2 +-
>   drivers/clk/meson/Kconfig                     | 46 +++++++++----------
>   drivers/clk/meson/Makefile                    |  1 -
>   drivers/clk/meson/a1-peripherals.c            |  2 +-
>   drivers/clk/meson/a1-pll.c                    |  2 +-
>   drivers/clk/meson/axg-aoclk.c                 |  2 +-
>   drivers/clk/meson/axg-audio.c                 |  2 +-
>   drivers/clk/meson/axg.c                       |  2 +-
>   drivers/clk/meson/c3-peripherals.c            |  2 +-
>   drivers/clk/meson/c3-pll.c                    |  2 +-
>   drivers/clk/meson/clk-cpu-dyndiv.c            |  2 +-
>   drivers/clk/meson/clk-dualdiv.c               |  2 +-
>   drivers/clk/meson/clk-mpll.c                  |  2 +-
>   drivers/clk/meson/clk-phase.c                 |  2 +-
>   drivers/clk/meson/clk-pll.c                   |  2 +-
>   drivers/clk/meson/g12a-aoclk.c                |  2 +-
>   drivers/clk/meson/g12a.c                      |  2 +-
>   drivers/clk/meson/gxbb-aoclk.c                |  2 +-
>   drivers/clk/meson/gxbb.c                      |  2 +-
>   drivers/clk/meson/meson-aoclk.h               |  2 +-
>   drivers/clk/meson/meson-eeclk.c               |  2 +-
>   drivers/clk/meson/meson-eeclk.h               |  2 +-
>   drivers/clk/meson/meson8-ddr.c                |  2 +-
>   drivers/clk/meson/meson8b.c                   |  2 +-
>   drivers/clk/meson/s4-peripherals.c            |  2 +-
>   drivers/clk/meson/s4-pll.c                    |  2 +-
>   drivers/clk/meson/sclk-div.c                  |  2 +-
>   drivers/clk/meson/vclk.h                      |  2 +-
>   drivers/clk/meson/vid-pll-div.c               |  2 +-
>   .../meson => include/linux/clk}/clk-regmap.h  |  0
>   32 files changed, 53 insertions(+), 53 deletions(-)
>   rename drivers/clk/{meson => }/clk-regmap.c (99%)
>   rename {drivers/clk/meson => include/linux/clk}/clk-regmap.h (100%)
> 
<snip>

I don't have objections, but I think Stephen didn't like the idea
a few years ago, but perhaps it has changed...

Anyway, take my:
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>

Thanks,
Neil
Jerome Brunet Oct. 2, 2024, 1:21 p.m. UTC | #2
On Wed 02 Oct 2024 at 13:20, Neil Armstrong <neil.armstrong@linaro.org> wrote:

> On 02/10/2024 12:48, Conor Dooley wrote:
>> From: Conor Dooley <conor.dooley@microchip.com>
>> I like this one better than qualcomms and wish to use it for the
>> PolarFire SoC clock drivers.
>> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>> ---
>>   drivers/clk/Kconfig                           |  4 ++
>>   drivers/clk/Makefile                          |  1 +
>>   drivers/clk/{meson => }/clk-regmap.c          |  2 +-
>>   drivers/clk/meson/Kconfig                     | 46 +++++++++----------
>>   drivers/clk/meson/Makefile                    |  1 -
>>   drivers/clk/meson/a1-peripherals.c            |  2 +-
>>   drivers/clk/meson/a1-pll.c                    |  2 +-
>>   drivers/clk/meson/axg-aoclk.c                 |  2 +-
>>   drivers/clk/meson/axg-audio.c                 |  2 +-
>>   drivers/clk/meson/axg.c                       |  2 +-
>>   drivers/clk/meson/c3-peripherals.c            |  2 +-
>>   drivers/clk/meson/c3-pll.c                    |  2 +-
>>   drivers/clk/meson/clk-cpu-dyndiv.c            |  2 +-
>>   drivers/clk/meson/clk-dualdiv.c               |  2 +-
>>   drivers/clk/meson/clk-mpll.c                  |  2 +-
>>   drivers/clk/meson/clk-phase.c                 |  2 +-
>>   drivers/clk/meson/clk-pll.c                   |  2 +-
>>   drivers/clk/meson/g12a-aoclk.c                |  2 +-
>>   drivers/clk/meson/g12a.c                      |  2 +-
>>   drivers/clk/meson/gxbb-aoclk.c                |  2 +-
>>   drivers/clk/meson/gxbb.c                      |  2 +-
>>   drivers/clk/meson/meson-aoclk.h               |  2 +-
>>   drivers/clk/meson/meson-eeclk.c               |  2 +-
>>   drivers/clk/meson/meson-eeclk.h               |  2 +-
>>   drivers/clk/meson/meson8-ddr.c                |  2 +-
>>   drivers/clk/meson/meson8b.c                   |  2 +-
>>   drivers/clk/meson/s4-peripherals.c            |  2 +-
>>   drivers/clk/meson/s4-pll.c                    |  2 +-
>>   drivers/clk/meson/sclk-div.c                  |  2 +-
>>   drivers/clk/meson/vclk.h                      |  2 +-
>>   drivers/clk/meson/vid-pll-div.c               |  2 +-
>>   .../meson => include/linux/clk}/clk-regmap.h  |  0
>>   32 files changed, 53 insertions(+), 53 deletions(-)
>>   rename drivers/clk/{meson => }/clk-regmap.c (99%)
>>   rename {drivers/clk/meson => include/linux/clk}/clk-regmap.h (100%)
>> 
> <snip>
>
> I don't have objections, but I think Stephen didn't like the idea
> a few years ago, but perhaps it has changed...
>
> Anyway, take my:
> Acked-by: Neil Armstrong <neil.armstrong@linaro.org>

We had a similar discussion 3y ago indeed:
https://lore.kernel.org/linux-clk/162734682512.2368309.12015873010777083014@swboyd.mtv.corp.google.com/

There are needs for a common regmap backed clocks indeed, but allowing
meson flavored regmap clocks to spread in the kernel was not really the
prefered way to do it. 

IIRC, Stephen's idea was more the bring regmap support in clk-gate.c,
clk-mux, etc ... I'm not quite sure how make iomem and regmap co-exist
in a manageable/maintainable way within those drivers (without adding yet
another level of abstraction I mean) ? Silently creating a regmap maybe
? but that's probably a bit heavy. I did not really had time to dig more
on this, I guess no one did.

I don't really have a preference one way or the other but if it is going
to be exposed in 'include/linux', we need to be sure that's how we want
to do it. With clocks poping in many driver subsystems, it will
difficult to change afterward. 

>
> Thanks,
> Neil
Conor Dooley Oct. 3, 2024, 11:33 a.m. UTC | #3
On Wed, Oct 02, 2024 at 03:21:16PM +0200, Jerome Brunet wrote:
> On Wed 02 Oct 2024 at 13:20, Neil Armstrong <neil.armstrong@linaro.org> wrote:
> 
> > On 02/10/2024 12:48, Conor Dooley wrote:
> >> From: Conor Dooley <conor.dooley@microchip.com>
> >> I like this one better than qualcomms and wish to use it for the
> >> PolarFire SoC clock drivers.
> >> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> >> ---
> >>   drivers/clk/Kconfig                           |  4 ++
> >>   drivers/clk/Makefile                          |  1 +
> >>   drivers/clk/{meson => }/clk-regmap.c          |  2 +-
> >>   drivers/clk/meson/Kconfig                     | 46 +++++++++----------
> >>   drivers/clk/meson/Makefile                    |  1 -
> >>   drivers/clk/meson/a1-peripherals.c            |  2 +-
> >>   drivers/clk/meson/a1-pll.c                    |  2 +-
> >>   drivers/clk/meson/axg-aoclk.c                 |  2 +-
> >>   drivers/clk/meson/axg-audio.c                 |  2 +-
> >>   drivers/clk/meson/axg.c                       |  2 +-
> >>   drivers/clk/meson/c3-peripherals.c            |  2 +-
> >>   drivers/clk/meson/c3-pll.c                    |  2 +-
> >>   drivers/clk/meson/clk-cpu-dyndiv.c            |  2 +-
> >>   drivers/clk/meson/clk-dualdiv.c               |  2 +-
> >>   drivers/clk/meson/clk-mpll.c                  |  2 +-
> >>   drivers/clk/meson/clk-phase.c                 |  2 +-
> >>   drivers/clk/meson/clk-pll.c                   |  2 +-
> >>   drivers/clk/meson/g12a-aoclk.c                |  2 +-
> >>   drivers/clk/meson/g12a.c                      |  2 +-
> >>   drivers/clk/meson/gxbb-aoclk.c                |  2 +-
> >>   drivers/clk/meson/gxbb.c                      |  2 +-
> >>   drivers/clk/meson/meson-aoclk.h               |  2 +-
> >>   drivers/clk/meson/meson-eeclk.c               |  2 +-
> >>   drivers/clk/meson/meson-eeclk.h               |  2 +-
> >>   drivers/clk/meson/meson8-ddr.c                |  2 +-
> >>   drivers/clk/meson/meson8b.c                   |  2 +-
> >>   drivers/clk/meson/s4-peripherals.c            |  2 +-
> >>   drivers/clk/meson/s4-pll.c                    |  2 +-
> >>   drivers/clk/meson/sclk-div.c                  |  2 +-
> >>   drivers/clk/meson/vclk.h                      |  2 +-
> >>   drivers/clk/meson/vid-pll-div.c               |  2 +-
> >>   .../meson => include/linux/clk}/clk-regmap.h  |  0
> >>   32 files changed, 53 insertions(+), 53 deletions(-)
> >>   rename drivers/clk/{meson => }/clk-regmap.c (99%)
> >>   rename {drivers/clk/meson => include/linux/clk}/clk-regmap.h (100%)
> >> 
> > <snip>
> >
> > I don't have objections, but I think Stephen didn't like the idea
> > a few years ago, but perhaps it has changed...
> >
> > Anyway, take my:
> > Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
> 
> We had a similar discussion 3y ago indeed:
> https://lore.kernel.org/linux-clk/162734682512.2368309.12015873010777083014@swboyd.mtv.corp.google.com/
> 
> There are needs for a common regmap backed clocks indeed, but allowing
> meson flavored regmap clocks to spread in the kernel was not really the
> prefered way to do it. 

Cool, thanks for that link.

> IIRC, Stephen's idea was more the bring regmap support in clk-gate.c,
> clk-mux, etc ... I'm not quite sure how make iomem and regmap co-exist
> in a manageable/maintainable way within those drivers (without adding yet
> another level of abstraction I mean) ? Silently creating a regmap maybe
> ? but that's probably a bit heavy. I did not really had time to dig more
> on this, I guess no one did.

I guess I have some motivation to looking into it at the moment. I had
my reservations about the Meson approach too, liking it more than
Qualcomm's didn't mean I completely liked it.
It was already my intention to implement point b of your mail, had the
general idea here been acceptable, cos that's a divergence from how the
generic clock types (that the driver in question currently uses) work.
And on that note, I just noticed I left the mild-annoyance variable name
"sigh" in the submitted driver changes, which I had used for the
clk_regmap struct that your point b in the link relates to.

> I don't really have a preference one way or the other but if it is going
> to be exposed in 'include/linux', we need to be sure that's how we want
> to do it. With clocks poping in many driver subsystems, it will
> difficult to change afterward. 

Yeah, I agree. I didn't expect this to go in right away, and I also
didn't want to surge ahead on some rework of the clock types, were
people to hate even the reuse.
Conor Dooley Nov. 6, 2024, 12:56 p.m. UTC | #4
Stephen,

On Thu, Oct 03, 2024 at 12:33:40PM +0100, Conor Dooley wrote:
> On Wed, Oct 02, 2024 at 03:21:16PM +0200, Jerome Brunet wrote:
> > On Wed 02 Oct 2024 at 13:20, Neil Armstrong <neil.armstrong@linaro.org> wrote:
> > 
> > > On 02/10/2024 12:48, Conor Dooley wrote:
> > >> From: Conor Dooley <conor.dooley@microchip.com>
> > >> I like this one better than qualcomms and wish to use it for the
> > >> PolarFire SoC clock drivers.
> > >> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > >> ---
> > >>   drivers/clk/Kconfig                           |  4 ++
> > >>   drivers/clk/Makefile                          |  1 +
> > >>   drivers/clk/{meson => }/clk-regmap.c          |  2 +-
> > >>   drivers/clk/meson/Kconfig                     | 46 +++++++++----------
> > >>   drivers/clk/meson/Makefile                    |  1 -
> > >>   drivers/clk/meson/a1-peripherals.c            |  2 +-
> > >>   drivers/clk/meson/a1-pll.c                    |  2 +-
> > >>   drivers/clk/meson/axg-aoclk.c                 |  2 +-
> > >>   drivers/clk/meson/axg-audio.c                 |  2 +-
> > >>   drivers/clk/meson/axg.c                       |  2 +-
> > >>   drivers/clk/meson/c3-peripherals.c            |  2 +-
> > >>   drivers/clk/meson/c3-pll.c                    |  2 +-
> > >>   drivers/clk/meson/clk-cpu-dyndiv.c            |  2 +-
> > >>   drivers/clk/meson/clk-dualdiv.c               |  2 +-
> > >>   drivers/clk/meson/clk-mpll.c                  |  2 +-
> > >>   drivers/clk/meson/clk-phase.c                 |  2 +-
> > >>   drivers/clk/meson/clk-pll.c                   |  2 +-
> > >>   drivers/clk/meson/g12a-aoclk.c                |  2 +-
> > >>   drivers/clk/meson/g12a.c                      |  2 +-
> > >>   drivers/clk/meson/gxbb-aoclk.c                |  2 +-
> > >>   drivers/clk/meson/gxbb.c                      |  2 +-
> > >>   drivers/clk/meson/meson-aoclk.h               |  2 +-
> > >>   drivers/clk/meson/meson-eeclk.c               |  2 +-
> > >>   drivers/clk/meson/meson-eeclk.h               |  2 +-
> > >>   drivers/clk/meson/meson8-ddr.c                |  2 +-
> > >>   drivers/clk/meson/meson8b.c                   |  2 +-
> > >>   drivers/clk/meson/s4-peripherals.c            |  2 +-
> > >>   drivers/clk/meson/s4-pll.c                    |  2 +-
> > >>   drivers/clk/meson/sclk-div.c                  |  2 +-
> > >>   drivers/clk/meson/vclk.h                      |  2 +-
> > >>   drivers/clk/meson/vid-pll-div.c               |  2 +-
> > >>   .../meson => include/linux/clk}/clk-regmap.h  |  0
> > >>   32 files changed, 53 insertions(+), 53 deletions(-)
> > >>   rename drivers/clk/{meson => }/clk-regmap.c (99%)
> > >>   rename {drivers/clk/meson => include/linux/clk}/clk-regmap.h (100%)
> > >> 
> > > <snip>
> > >
> > > I don't have objections, but I think Stephen didn't like the idea
> > > a few years ago, but perhaps it has changed...
> > >
> > > Anyway, take my:
> > > Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
> > 
> > We had a similar discussion 3y ago indeed:
> > https://lore.kernel.org/linux-clk/162734682512.2368309.12015873010777083014@swboyd.mtv.corp.google.com/
> > 
> > There are needs for a common regmap backed clocks indeed, but allowing
> > meson flavored regmap clocks to spread in the kernel was not really the
> > prefered way to do it. 
> 
> Cool, thanks for that link.
> 
> > IIRC, Stephen's idea was more the bring regmap support in clk-gate.c,
> > clk-mux, etc ... I'm not quite sure how make iomem and regmap co-exist
> > in a manageable/maintainable way within those drivers (without adding yet
> > another level of abstraction I mean) ? Silently creating a regmap maybe
> > ? but that's probably a bit heavy. I did not really had time to dig more
> > on this, I guess no one did.
> 
> I guess I have some motivation to looking into it at the moment. I had
> my reservations about the Meson approach too, liking it more than
> Qualcomm's didn't mean I completely liked it.
> It was already my intention to implement point b of your mail, had the
> general idea here been acceptable, cos that's a divergence from how the
> generic clock types (that the driver in question currently uses) work.
> And on that note, I just noticed I left the mild-annoyance variable name
> "sigh" in the submitted driver changes, which I had used for the
> clk_regmap struct that your point b in the link relates to.
> 
> > I don't really have a preference one way or the other but if it is going
> > to be exposed in 'include/linux', we need to be sure that's how we want
> > to do it. With clocks poping in many driver subsystems, it will
> > difficult to change afterward. 
> 
> Yeah, I agree. I didn't expect this to go in right away, and I also
> didn't want to surge ahead on some rework of the clock types, were
> people to hate even the reuse.

Hmm, so how (in-)complete of a regmap implementation can I get away
with? I only need clk-gate and clk-divider for this patchset...

Shoving the regmap into the clk structs makes things pretty trivial as I
don't need to do anything special in any function other than
clk_*_readl()/clk_*_writel() and the registration code. A flag isn't
even needed to determine if a clock is a regmap one I don't think, since
you can just check if the regmap pointer is non-NULL. My use case doesn't
actually need the registration code changes either as, currently, only reg
gets set at runtime, but leaving that out is a level of incomplete I'd not
let myself away with.
Obviously shoving the extra members into the clk structs has the downside
of taking up a pointer and a offset worth of memory for each clock of
that type registered, but it is substantially easier to support devices
with multiple regmaps that way. Probably moot though since the approach you
suggested in the thread linked above that implements a clk_hw_get_regmap()
has to store a pointer to the regmap's identifier which would take up an
identical amount of memory.

I don't really care which way you want it done, both are pretty easy to
implement if I can get away with just doing so for the two standard
clock types that I am using - is it okay to just do those two?

Cheers,
Conor.
Stephen Boyd Nov. 15, 2024, 1:29 a.m. UTC | #5
Quoting Conor Dooley (2024-11-06 04:56:25)
> On Thu, Oct 03, 2024 at 12:33:40PM +0100, Conor Dooley wrote:
> > > IIRC, Stephen's idea was more the bring regmap support in clk-gate.c,
> > > clk-mux, etc ... I'm not quite sure how make iomem and regmap co-exist
> > > in a manageable/maintainable way within those drivers (without adding yet
> > > another level of abstraction I mean) ? Silently creating a regmap maybe
> > > ? but that's probably a bit heavy. I did not really had time to dig more
> > > on this, I guess no one did.
> > 
> > I guess I have some motivation to looking into it at the moment. I had
> > my reservations about the Meson approach too, liking it more than
> > Qualcomm's didn't mean I completely liked it.
> > It was already my intention to implement point b of your mail, had the
> > general idea here been acceptable, cos that's a divergence from how the
> > generic clock types (that the driver in question currently uses) work.
> > And on that note, I just noticed I left the mild-annoyance variable name
> > "sigh" in the submitted driver changes, which I had used for the
> > clk_regmap struct that your point b in the link relates to.
> > 
> > > I don't really have a preference one way or the other but if it is going
> > > to be exposed in 'include/linux', we need to be sure that's how we want
> > > to do it. With clocks poping in many driver subsystems, it will
> > > difficult to change afterward. 
> > 
> > Yeah, I agree. I didn't expect this to go in right away, and I also
> > didn't want to surge ahead on some rework of the clock types, were
> > people to hate even the reuse.
> 
> Hmm, so how (in-)complete of a regmap implementation can I get away
> with? I only need clk-gate and clk-divider for this patchset...
> 
> Shoving the regmap into the clk structs makes things pretty trivial as I
> don't need to do anything special in any function other than
> clk_*_readl()/clk_*_writel() and the registration code. A flag isn't
> even needed to determine if a clock is a regmap one I don't think, since
> you can just check if the regmap pointer is non-NULL.

For the basic clk types I think it would be good to leave the old stuff
alone. We have already split the logic out into helpers, so I wonder if
we can do this better by making kernel modules for the different basic
regmap clk types and exposing registration APIs. If we force drivers
that use the basic regmap types to 'select' the module then we'll make
it so that we don't include code that isn't used anywhere. That's one of
the problems with the basic clk types, it's always built. It also lets
us avoid making regmap a dependency for the clk framework at large.

Doing that would also let us avoid the flag because it will be explicit
in any registration API, clk_register_divider() vs.
clk_register_regmap_divider(). Yes we duplicate some boiler plate logic
around read-only and registration paths, but this is alright as long as
we can share most of the code and gain the advantage of removing the
code entirely when it isn't used.

I wonder if we can even make a regmap on the fly for the iomem pointers
so that clk_divider_readl() can always use the regmap API to access the
hardware. Sounds wasteful but maybe it would work.

> My use case doesn't
> actually need the registration code changes either as, currently, only reg
> gets set at runtime, but leaving that out is a level of incomplete I'd not
> let myself away with.
> Obviously shoving the extra members into the clk structs has the downside
> of taking up a pointer and a offset worth of memory for each clock of
> that type registered, but it is substantially easier to support devices
> with multiple regmaps that way. Probably moot though since the approach you
> suggested in the thread linked above that implements a clk_hw_get_regmap()
> has to store a pointer to the regmap's identifier which would take up an
> identical amount of memory.

We don't need to store the regmap identifier in the struct clk. We can
store it in the 'struct clk_init_data' with some new field, and only do
that when/if we actually need to. We would need to pass the init data to
the clk_ops::init() callback though. We currently knock that out during
registration so that clk_hw->init is NULL. Probably we can just set that
to NULL after the init routine runs in __clk_core_init().

Long story short, don't add something to 'struct clk_core', 'struct
clk', or 'struct clk_hw' for these details. We can have a 'struct
clk_regmap_hw' that everyone else can build upon:

  struct clk_regmap_hw {
        struct regmap *regmap;
        struct clk_hw hw;
  };

and then set the regmap pointer during registration in
clk_hw_init_regmap().

int clk_hw_init_regmap(struct clk_hw *hw)
{
	struct device *dev;
	struct regmap *regmap;
	struct clk_regmap_hw *rhw;

	rhw = clk_hw_to_clk_regmap_hw(hw);

	dev = clk_hw_get_dev(hw);
	if (!dev)
		return -EINVAL;

	regmap = dev_get_regmap(dev, hw->init->regmap_name);
	if (!regmap)
		return -EINVAL; // Print helpful message
	rhw->regmap = regmap;

	return 0;
}

or we can even make it so that there's clk_hw_init_regmap() and
clk_hw_init_regmap_name() so that drivers can have multiple functions if
the clks need different regmaps.

int my_init_regmap(struct clk_hw *hw)
{
	int ret;

	ret = clk_hw_init_regmap_name(hw, "my_name");
	...
}

If you don't need the multiple regmap support then it's fine to punt
here until later.

> 
> I don't really care which way you want it done, both are pretty easy to
> implement if I can get away with just doing so for the two standard
> clock types that I am using - is it okay to just do those two?
> 

Of course, doing only what is minimally required is better than changing
everything if you're not sure the approach is going to land.