[v15,00/11] Convert PWM period and duty cycle to u64

Message

Guru Das Srinagesh May 26, 2020, 5:35 p.m. UTC

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 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                    | 53 +++++++++++++++++++++++++-----
 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, 79 insertions(+), 35 deletions(-)