Subject: Re: [PATCH v16 00/11] Convert PWM period and duty cycle to u64

From: Guru Das Srinagesh <[email-masked]>
Date: Thu, 11 Jun 2020 09:55:05 -0700

On Tue, Jun 02, 2020 at 03:31:04PM -0700, Guru Das Srinagesh wrote:
> Because period and duty cycle are defined in the PWM framework structs as ints
> with units of nanoseconds, the maximum time duration that can be set is limited
> to ~2.147 seconds. Consequently, applications desiring to set greater time
> periods via the PWM framework are not be able to do so - like, for instance,
> causing an LED to blink at an interval of 5 seconds.
> 
> Redefining the period and duty cycle struct members in the core PWM framework
> structs as u64 values will enable larger time durations to be set and solve
> this problem. Such a change to the framework mandates that drivers using these
> struct members (and corresponding helper functions) also be modified correctly
> in order to prevent compilation errors.
> 
> This patch series introduces the changes to all the drivers first, followed by
> the framework change at the very end so that when the latter is applied, all
> the drivers are in good shape and there are no compilation errors.
> 
> Changes from v15:
>   -  Rebased to tip of for-next.
> 
> Changes from v14:
>   - Collected Uwe's Acked-by for the pwm core patch.
>   - Addressed comments in pwm-clps711x.c.
> 
> Changes from v13:
>   - Pruned cc-list and added same (reduced) set of reviewers to all patches.
>   - Added Lee Jones' Acked-by to the pwm_bl.c patch.
>   - Added Jani Nikula's Acked-by to intel-panel.c patch.
>   - Added Stephen Boyd's Acked-by to pwm-clk.c patch.
>   - Addressed Geert's review comments in clps711x.c patch.
> 
> Changes from v12:
>   - Rebased to tip of for-next
>   - Collected Acked-by for sun4i
>   - Reworked patch for intel-panel.c due to rebase, dropped Jani's Acked-by as
>     a result
> 
> Changes from v11:
>   - Rebased to tip of for-next.
>   - Collected "Acked-by:" for v7 (unchanged) of pwm: sifive: [4]
>   - Squished stm32-lp.c change with final patch in series
>   - sun4i: Used nsecs_to_jiffies()
>   - imx27: Added overflow handling logic
>   - clps711x: Corrected the if condition for skipping the division
>   - clk: pwm: Reverted to v8 version, added check to prevent division-by-zero
> 
> Changes from v10:
>   - Carefully added back all the "Reviewed-by: " and "Acked-by: " tags received
>     so far that had gotten missed in v9. No other changes.
> 
> Changes from v9:
>   - Gathered the received "Reviewed-by: " tag
>   - Added back the clk-pwm.c patch because kbuild test robot complained [3]
>     and addressed received review comments.
>   - clps711x: Addressed review comments.
> 
> Changes from v8:
>   - Gathered all received "Acked-by: " and "Reviewed-by: " tags
>   - Dropped patch to clk-pwm.c for reasons mentiond in [2]
>   - Expanded audience of unreviewed patches
> 
> Changes from v7:
>   - Changed commit messages of all patches to be brief and to the point.
>   - Added explanation of change in cover letter.
>   - Dropped change to pwm-sti.c as upon review it was unnecessary as struct
>     pwm_capture is not being modified in the PWM core.
> 
> Changes from v6:
>   - Split out the driver changes out into separate patches, one patch per file
>     for ease of reviewing.
> 
> Changes from v5:
>   - Dropped the conversion of struct pwm_capture to u64 for reasons mentioned
>     in https://www.spinics.net/lists/linux-pwm/msg11541.html
> 
> Changes from v4:
>   - Split the patch into two: one for changes to the drivers, and the actual
>     switch to u64 for ease of reverting should the need arise.
>   - Re-examined the patch and made the following corrections:
>       * intel_panel.c:
> 	DIV64_U64_ROUND_UP -> DIV_ROUND_UP_ULL (as only the numerator would be
> 	64-bit in this case).
>       * pwm-sti.c:
> 	do_div -> div_u64 (do_div is optimized only for x86 architectures, and
> 	div_u64's comment block suggests to use this as much as possible).
> 
> Changes from v3:
>   - Rebased to current tip of for-next.
> 
> Changes from v2:
>   - Fixed %u -> %llu in a dev_dbg in pwm-stm32-lp.c, thanks to kbuild test robot
>   - Added a couple of fixes to pwm-imx-tpm.c and pwm-sifive.c
> 
> Changes from v1:
>   - Fixed compilation errors seen when compiling for different archs.
> 
> v1:
>   - Reworked the change pushed upstream earlier [1] so as to not add an
>     extension to an obsolete API. With this change, pwm_ops->apply() can be
>     used to set pwm_state parameters as usual.
> 
> [1] https://lore.kernel.org/lkml/20190916140048.GB7488@ulmo/
> [2] https://lore.kernel.org/lkml/20200312190859.GA19605@xxxxxxxxxxxxxx/
> [3] https://www.spinics.net/lists/linux-pwm/msg11906.html
> [4] https://www.spinics.net/lists/linux-pwm/msg11986.html
> 
> Guru Das Srinagesh (11):
>   drm/i915: Use 64-bit division macro
>   hwmon: pwm-fan: Use 64-bit division macro
>   ir-rx51: Use 64-bit division macro
>   pwm: clps711x: Use 64-bit division macro
>   pwm: pwm-imx-tpm: Use 64-bit division macro
>   pwm: imx27: Use 64-bit division macro and function
>   pwm: sifive: Use 64-bit division macro
>   pwm: sun4i: Use nsecs_to_jiffies to avoid a division
>   backlight: pwm_bl: Use 64-bit division function
>   clk: pwm: Use 64-bit division function
>   pwm: core: Convert period and duty cycle to u64
> 
>  drivers/clk/clk-pwm.c                      |  7 ++++-
>  drivers/gpu/drm/i915/display/intel_panel.c |  2 +-
>  drivers/hwmon/pwm-fan.c                    |  2 +-
>  drivers/media/rc/ir-rx51.c                 |  3 +-
>  drivers/pwm/core.c                         | 14 ++++-----
>  drivers/pwm/pwm-clps711x.c                 |  2 +-
>  drivers/pwm/pwm-imx-tpm.c                  |  2 +-
>  drivers/pwm/pwm-imx27.c                    | 48 ++++++++++++++++++++++++++----
>  drivers/pwm/pwm-sifive.c                   |  2 +-
>  drivers/pwm/pwm-stm32-lp.c                 |  2 +-
>  drivers/pwm/pwm-sun4i.c                    |  2 +-
>  drivers/pwm/sysfs.c                        |  8 ++---
>  drivers/video/backlight/pwm_bl.c           |  3 +-
>  include/linux/pwm.h                        | 12 ++++----
>  14 files changed, 77 insertions(+), 32 deletions(-)
> 
> -- 

Hello Thierry, Uwe, Lee,

Gentle reminder for this patch series :) Earlier discussions on next
steps were as per [1] and [2].

[1] https://lore.kernel.org/lkml/20200522125028.GG2163848@ulmo/
[2] https://lore.kernel.org/lkml/20200526065935.GA3628@dell/

Thank you.

Guru Das.

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