Message-ID: <20200611182430.GA2293927@ulmo>
Date:   Thu, 11 Jun 2020 20:24:30 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Guru Das Srinagesh <gurus@...eaurora.org>
Cc:     linux-pwm@...r.kernel.org,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Subbaraman Narayanamurthy <subbaram@...eaurora.org>,
        David Collins <collinsd@...eaurora.org>,
        linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v16 00/11] Convert PWM period and duty cycle to u64

On Thu, Jun 11, 2020 at 09:55:05AM -0700, Guru Das Srinagesh wrote:
> 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].

Hi Guru,

I ended up deciding against queueing this for v5.8-rc1 because I want
this to soak for a bit in linux-next. I'll apply them early next week
after v5.8-rc1 is out.

Thierry

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