[v7,0/5] clk: ti: add am33xx spread spectrum clock support

Message

Dario Binacchi June 2, 2021, 3 p.m. UTC

As reported by the TI spruh73x/spruhl7x RM, MPU and LCD modules support
spread spectrum clocking (SSC) on their output clocks. SSC is used to
spread the spectral peaking of the clock to reduce any electromagnetic
interference (EMI) that may be caused due to the clock’s fundamental
or any of its harmonics.
The series allows you to enable and adjust the spread spectrum clocking
for all am33xx/am43xx PLLs for which it is supported. All these issues
have been fixed.


Previous versions of the series did not supported SSC for am43xx SOCs,
causing clock registration failure for DPLLs. Furthermore, for am33xx
SOCs, clock registration failed for DPLLs for which SSC is not supported.

Changes in v7:
- Add Tony Lindgren acked tag.

Changes in v6:
- Add Tero Kristo review tag.

Changes in v5:
- Remove ssc_ack_mask field from dpll_data structure. It was not used.
- Change ssc_downspread type from u8 to bool in dpll_data structure.

Changes in v4:
- Add Stephen Boyd review tag.
- Add Rob Herring review tag.
- Add SSC registers for CORE, DDR and PER PLLs.
- Update commit message.
- Update commit message.

Changes in v3:
- Add '-hz' suffix to "ti,ssc-modfreq" binding.
- Add Tony Lindgren acked tag.
- Use "ti,ssc-modfreq-hz" binding instead of "ti,ssc-modfreq".

Changes in v2:
- Remove SSC registers from dpll_core_ck@490 node (SSC is not supported)
- Add SSC registers to dpll_mpu_ck@488 node.
- Move the DT changes to the previous patch in the series.

Dario Binacchi (5):
  clk: ti: fix typo in routine description
  dt-bindings: ti: dpll: add spread spectrum support
  ARM: dts: am33xx-clocks: add spread spectrum support
  ARM: dts: am43xx-clocks: add spread spectrum support
  clk: ti: add am33xx/am43xx spread spectrum clock support

 .../devicetree/bindings/clock/ti/dpll.txt     | 20 +++++
 arch/arm/boot/dts/am33xx-clocks.dtsi          | 10 +--
 arch/arm/boot/dts/am43xx-clocks.dtsi          | 12 +--
 drivers/clk/ti/dpll.c                         | 39 +++++++++
 drivers/clk/ti/dpll3xxx.c                     | 87 ++++++++++++++++++-
 include/linux/clk/ti.h                        | 22 +++++
 6 files changed, 178 insertions(+), 12 deletions(-)

Comments

Tony Lindgren June 4, 2021, 7:24 a.m. UTC | #1

Hi,

* Dario Binacchi <[e-mail]> [210602 15:00]:
> 
> As reported by the TI spruh73x/spruhl7x RM, MPU and LCD modules support
> spread spectrum clocking (SSC) on their output clocks. SSC is used to
> spread the spectral peaking of the clock to reduce any electromagnetic
> interference (EMI) that may be caused due to the clock’s fundamental
> or any of its harmonics.
> The series allows you to enable and adjust the spread spectrum clocking
> for all am33xx/am43xx PLLs for which it is supported. All these issues
> have been fixed.
> 
> 
> Previous versions of the series did not supported SSC for am43xx SOCs,
> causing clock registration failure for DPLLs. Furthermore, for am33xx
> SOCs, clock registration failed for DPLLs for which SSC is not supported.

Looks good to me, probably best to queue this all via the clock tree.

Regards,

Tony