| Message ID | 20210226141411.2517368-3-linux@rasmusvillemoes.dk (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
| Series | add ripple counter dt binding and driver | expand |
> -----Original Message----- > From: Rasmus Villemoes <linux@rasmusvillemoes.dk> > Sent: Friday, February 26, 2021 9:14 AM > To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; Rob Herring > <robh+dt@kernel.org> > Cc: devicetree@vger.kernel.org; linux-kernel@vger.kernel.org; Arnd Bergmann > <arnd@arndb.de>; linux-clk@vger.kernel.org; Rasmus Villemoes > <linux@rasmusvillemoes.dk> > Subject: [PATCH 2/2] drivers: misc: add ripple counter driver > > The only purpose of this driver is to serve as a consumer of the input > clock, to prevent it from being disabled by clk_disable_unused(). > > Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> > --- > drivers/misc/Kconfig | 7 +++++++ > drivers/misc/Makefile | 1 + > drivers/misc/ripple-ctr.c | 31 +++++++++++++++++++++++++++++++ > 3 files changed, 39 insertions(+) > create mode 100644 drivers/misc/ripple-ctr.c > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig > index f532c59bb59b..44b0b6ce42df 100644 > --- a/drivers/misc/Kconfig > +++ b/drivers/misc/Kconfig > @@ -445,6 +445,13 @@ config HISI_HIKEY_USB > switching between the dual-role USB-C port and the USB-A host ports > using only one USB controller. > > +config RIPPLE_CTR > + tristate "Trivial ripple counter driver" > + help > + This provides a stub driver for a ripple counter, whose > + only purpose is to request and enable the clock source > + driving the counter. > + > source "drivers/misc/c2port/Kconfig" > source "drivers/misc/eeprom/Kconfig" > source "drivers/misc/cb710/Kconfig" > diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile > index 99b6f15a3c70..d560163068a9 100644 > --- a/drivers/misc/Makefile > +++ b/drivers/misc/Makefile > @@ -56,3 +56,4 @@ obj-$(CONFIG_HABANA_AI) += habanalabs/ > obj-$(CONFIG_UACCE) += uacce/ > obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o > obj-$(CONFIG_HISI_HIKEY_USB) += hisi_hikey_usb.o > +obj-$(CONFIG_RIPPLE_CTR) += ripple-ctr.o > diff --git a/drivers/misc/ripple-ctr.c b/drivers/misc/ripple-ctr.c > new file mode 100644 > index 000000000000..f086eaf335df > --- /dev/null > +++ b/drivers/misc/ripple-ctr.c > @@ -0,0 +1,31 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +#include <linux/clk.h> > +#include <linux/err.h> > +#include <linux/mod_devicetable.h> > +#include <linux/module.h> > +#include <linux/platform_device.h> > + > +static int ripple_ctr_probe(struct platform_device *pdev) > +{ > + struct clk *clk; > + > + clk = devm_clk_get(&pdev->dev, NULL); > + if (IS_ERR(clk)) > + return PTR_ERR(clk); > + return clk_prepare_enable(clk); > +} > + > +static const struct of_device_id ripple_ctr_ids[] = { > + { .compatible = "linux,ripple-counter", }, > + { } > +}; > +MODULE_DEVICE_TABLE(of, ripple_ctr_ids); > + > +static struct platform_driver ripple_ctr_driver = { > + .driver = { > + .name = "ripple-counter", > + .of_match_table = ripple_ctr_ids, > + }, > + .probe = ripple_ctr_probe, > +}; > +module_platform_driver(ripple_ctr_driver); Missing MODULE_LICENSE() tag? See https://www.kernel.org/doc/html/latest/process/license-rules.html#license-identifiers > -- > 2.29.2
On Sun, Feb 28, 2021 at 11:07 AM Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Friday, February 26, 2021, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: >> >> The only purpose of this driver is to serve as a consumer of the input >> clock, to prevent it from being disabled by clk_disable_unused(). > > We have a clock API to do the same (something like marking it used or so) why do you need a driver? Example: https://elixir.bootlin.com/linux/latest/source/drivers/platform/x86/pmc_atom.c#L365 If it's a DT based platform I think you can make it somehow work thru DT.
On Sun, Feb 28, 2021 at 11:29 AM Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > > On Sun, Feb 28, 2021 at 11:07 AM Andy Shevchenko > <andy.shevchenko@gmail.com> wrote: > > On Friday, February 26, 2021, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: > >> > >> The only purpose of this driver is to serve as a consumer of the input > >> clock, to prevent it from being disabled by clk_disable_unused(). > > > > We have a clock API to do the same (something like marking it used or so) why do you need a driver? > > Example: > https://elixir.bootlin.com/linux/latest/source/drivers/platform/x86/pmc_atom.c#L365 > > If it's a DT based platform I think you can make it somehow work thru DT. Okay, briefly looking at the state of affairs [1] seems like you need to hack it into clock provider. [1]: https://elixir.bootlin.com/linux/latest/C/ident/CLK_IS_CRITICAL
On 28/02/2021 10.33, Andy Shevchenko wrote: > On Sun, Feb 28, 2021 at 11:29 AM Andy Shevchenko > <andy.shevchenko@gmail.com> wrote: >> >> On Sun, Feb 28, 2021 at 11:07 AM Andy Shevchenko >> <andy.shevchenko@gmail.com> wrote: >>> On Friday, February 26, 2021, Rasmus Villemoes <linux@rasmusvillemoes.dk> wrote: >>>> >>>> The only purpose of this driver is to serve as a consumer of the input >>>> clock, to prevent it from being disabled by clk_disable_unused(). >>> >>> We have a clock API to do the same (something like marking it used or so) why do you need a driver? >> >> Example: >> https://elixir.bootlin.com/linux/latest/source/drivers/platform/x86/pmc_atom.c#L365 >> >> If it's a DT based platform I think you can make it somehow work thru DT. > > Okay, briefly looking at the state of affairs [1] seems like you need > to hack it into clock provider. > > [1]: https://elixir.bootlin.com/linux/latest/C/ident/CLK_IS_CRITICAL > I did find CLK_IS_CRITICAL and CLK_IGNORE_UNUSED while trying to figure out how to handle this. However, while CLK_IS_CRITICAL is in principle settable via DT, the comment above of_clk_detect_critical() seems to make it clear that adding a call of that from the RTC driver is a total no-no. CLK_IGNORE_UNUSED can't be set at all from DT, and wouldn't solve the problem fully - while we can and do make sure the bootloader sets the appropriate bit in the RTCs registers, it's more robust if we also ensure the kernel explicitly enables the clock. But if there is some way to do this within the clk framework/existing bindings, I'm all ears - that's the reason I cc'ed the clk list. Rasmus
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig index f532c59bb59b..44b0b6ce42df 100644 --- a/drivers/misc/Kconfig +++ b/drivers/misc/Kconfig @@ -445,6 +445,13 @@ config HISI_HIKEY_USB switching between the dual-role USB-C port and the USB-A host ports using only one USB controller. +config RIPPLE_CTR + tristate "Trivial ripple counter driver" + help + This provides a stub driver for a ripple counter, whose + only purpose is to request and enable the clock source + driving the counter. + source "drivers/misc/c2port/Kconfig" source "drivers/misc/eeprom/Kconfig" source "drivers/misc/cb710/Kconfig" diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile index 99b6f15a3c70..d560163068a9 100644 --- a/drivers/misc/Makefile +++ b/drivers/misc/Makefile @@ -56,3 +56,4 @@ obj-$(CONFIG_HABANA_AI) += habanalabs/ obj-$(CONFIG_UACCE) += uacce/ obj-$(CONFIG_XILINX_SDFEC) += xilinx_sdfec.o obj-$(CONFIG_HISI_HIKEY_USB) += hisi_hikey_usb.o +obj-$(CONFIG_RIPPLE_CTR) += ripple-ctr.o diff --git a/drivers/misc/ripple-ctr.c b/drivers/misc/ripple-ctr.c new file mode 100644 index 000000000000..f086eaf335df --- /dev/null +++ b/drivers/misc/ripple-ctr.c @@ -0,0 +1,31 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +#include <linux/clk.h> +#include <linux/err.h> +#include <linux/mod_devicetable.h> +#include <linux/module.h> +#include <linux/platform_device.h> + +static int ripple_ctr_probe(struct platform_device *pdev) +{ + struct clk *clk; + + clk = devm_clk_get(&pdev->dev, NULL); + if (IS_ERR(clk)) + return PTR_ERR(clk); + return clk_prepare_enable(clk); +} + +static const struct of_device_id ripple_ctr_ids[] = { + { .compatible = "linux,ripple-counter", }, + { } +}; +MODULE_DEVICE_TABLE(of, ripple_ctr_ids); + +static struct platform_driver ripple_ctr_driver = { + .driver = { + .name = "ripple-counter", + .of_match_table = ripple_ctr_ids, + }, + .probe = ripple_ctr_probe, +}; +module_platform_driver(ripple_ctr_driver);
The only purpose of this driver is to serve as a consumer of the input clock, to prevent it from being disabled by clk_disable_unused(). Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> --- drivers/misc/Kconfig | 7 +++++++ drivers/misc/Makefile | 1 + drivers/misc/ripple-ctr.c | 31 +++++++++++++++++++++++++++++++ 3 files changed, 39 insertions(+) create mode 100644 drivers/misc/ripple-ctr.c