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

From: Guru Das Srinagesh
Date: Thu Jun 11 2020 - 12:55:11 EST


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.