[PATCH v12 00/11] Convert PWM period and duty cycle to u64

[PATCH v12 00/11] Convert PWM period and duty cycle to u64

[Guru Das Srinagesh]

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 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@codeaurora.org/
[3] https://www.spinics.net/lists/linux-pwm/msg11906.html
[4] https://www.spinics.net/lists/linux-pwm/msg11986.html

Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Richard Fontana <rfontana@redhat.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Yash Shah <yash.shah@sifive.com>

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: Cast period to u32 before use as divisor
  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                 |  5 ++-
 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, 82 insertions(+), 35 deletions(-)

-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 01/11] drm/i915: Use 64-bit division macro

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.duty_cycle's
datatype to u64, prepare for this transition by using DIV_ROUND_UP_ULL
to handle a 64-bit dividend.

Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
---
 drivers/gpu/drm/i915/display/intel_panel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
index 7b3ec6eb..b45eabf 100644
--- a/drivers/gpu/drm/i915/display/intel_panel.c
+++ b/drivers/gpu/drm/i915/display/intel_panel.c
@@ -1877,7 +1877,7 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 
 	panel->backlight.min = 0; /* 0% */
 	panel->backlight.max = 100; /* 100% */
-	panel->backlight.level = DIV_ROUND_UP(
+	panel->backlight.level = DIV_ROUND_UP_ULL(
 				 pwm_get_duty_cycle(panel->backlight.pwm) * 100,
 				 CRC_PMIC_PWM_PERIOD_NS);
 	panel->backlight.enabled = panel->backlight.level != 0;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 02/11] hwmon: pwm-fan: Use 64-bit division macro

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by using DIV_ROUND_UP_ULL to handle
a 64-bit dividend.

Cc: Kamil Debski <kamil@wypas.org>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Jean Delvare <jdelvare@suse.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: linux-hwmon@vger.kernel.org

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Acked-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/pwm-fan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/pwm-fan.c b/drivers/hwmon/pwm-fan.c
index 30b7b3e..17bb642 100644
--- a/drivers/hwmon/pwm-fan.c
+++ b/drivers/hwmon/pwm-fan.c
@@ -447,7 +447,7 @@ static int pwm_fan_resume(struct device *dev)
 		return 0;
 
 	pwm_get_args(ctx->pwm, &pargs);
-	duty = DIV_ROUND_UP(ctx->pwm_value * (pargs.period - 1), MAX_PWM);
+	duty = DIV_ROUND_UP_ULL(ctx->pwm_value * (pargs.period - 1), MAX_PWM);
 	ret = pwm_config(ctx->pwm, duty, pargs.period);
 	if (ret)
 		return ret;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 03/11] ir-rx51: Use 64-bit division macro

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.period's datatype
to u64, prepare for this transition by using DIV_ROUND_CLOSEST_ULL to
handle a 64-bit dividend.

Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: Richard Fontana <rfontana@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Allison Randal <allison@lohutok.net>
Cc: linux-media@vger.kernel.org

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Acked-by: Sean Young <sean@mess.org>
---
 drivers/media/rc/ir-rx51.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/media/rc/ir-rx51.c b/drivers/media/rc/ir-rx51.c
index 8574eda..9a5dfd7 100644
--- a/drivers/media/rc/ir-rx51.c
+++ b/drivers/media/rc/ir-rx51.c
@@ -241,7 +241,8 @@ static int ir_rx51_probe(struct platform_device *dev)
 	}
 
 	/* Use default, in case userspace does not set the carrier */
-	ir_rx51.freq = DIV_ROUND_CLOSEST(pwm_get_period(pwm), NSEC_PER_SEC);
+	ir_rx51.freq = DIV_ROUND_CLOSEST_ULL(pwm_get_period(pwm),
+			NSEC_PER_SEC);
 	pwm_put(pwm);
 
 	hrtimer_init(&ir_rx51.timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 04/11] pwm: clps711x: Cast period to u32 before use as divisor

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by typecasting it to u32.

Also, since the dividend is still a 32-bit number, any divisor greater
than the numerator will cause the quotient to be zero, so return 0 in
that case to efficiently skip the division.

Cc: Alexander Shiyan <shc_work@mail.ru>
Cc: Arnd Bergmann <arnd@arndb.de>

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/pwm/pwm-clps711x.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-clps711x.c b/drivers/pwm/pwm-clps711x.c
index 924d39a..0d368ac 100644
--- a/drivers/pwm/pwm-clps711x.c
+++ b/drivers/pwm/pwm-clps711x.c
@@ -43,7 +43,10 @@ static void clps711x_pwm_update_val(struct clps711x_chip *priv, u32 n, u32 v)
 static unsigned int clps711x_get_duty(struct pwm_device *pwm, unsigned int v)
 {
 	/* Duty cycle 0..15 max */
-	return DIV_ROUND_CLOSEST(v * 0xf, pwm->args.period);
+	if ((u32)pwm->args.period > (v * 0xf))
+		return 0;
+
+	return DIV_ROUND_CLOSEST(v * 0xf, (u32)pwm->args.period);
 }
 
 static int clps711x_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 05/11] pwm: pwm-imx-tpm: Use 64-bit division macro

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.period's datatype
to u64, prepare for this transition by using DIV64_U64_ROUND_CLOSEST to
handle a 64-bit divisor.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/pwm/pwm-imx-tpm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-imx-tpm.c b/drivers/pwm/pwm-imx-tpm.c
index 5f3d7f7..fcdf6be 100644
--- a/drivers/pwm/pwm-imx-tpm.c
+++ b/drivers/pwm/pwm-imx-tpm.c
@@ -124,7 +124,7 @@ static int pwm_imx_tpm_round_state(struct pwm_chip *chip,
 		real_state->duty_cycle = state->duty_cycle;
 
 	tmp = (u64)p->mod * real_state->duty_cycle;
-	p->val = DIV_ROUND_CLOSEST_ULL(tmp, real_state->period);
+	p->val = DIV64_U64_ROUND_CLOSEST(tmp, real_state->period);
 
 	real_state->polarity = state->polarity;
 	real_state->enabled = state->enabled;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 06/11] pwm: imx27: Use 64-bit division macro and function

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.period's
datatype to u64, prepare for this transition by using
DIV_ROUND_UP_ULL to handle a 64-bit dividend, and div64_u64 to handle a
64-bit divisor.

Also handle a possible overflow in the calculation of period_cycles when
both clk_rate and period are large numbers. This logic was unit-tested
out by calculating period_cycles using both the existing logic and the
proposed one, and the results are as below.

----------------------------------------------------------------------------
 clk_rate            period           existing            proposed
----------------------------------------------------------------------------
1000000000   18446744073709551615    18446744072    18446744073000000000
                   (U64_MAX)
----------------------------------------------------------------------------
1000000000        4294967291         4294967291         4294967291
----------------------------------------------------------------------------

Overflow occurs in the first case with the existing logic, whereas the
proposed logic handles it better, sacrificing some precision in a best-effort
attempt to handle overflow. As for the second case where there are
more typical values of period, the proposed logic handles that correctly
too.

Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP Linux Team <linux-imx@nxp.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Collins <collinsd@codeaurora.org>

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/pwm/pwm-imx27.c | 53 +++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 45 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index a6e40d4..164cb65 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -203,7 +203,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
 	sr = readl(imx->mmio_base + MX3_PWMSR);
 	fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr);
 	if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
-		period_ms = DIV_ROUND_UP(pwm_get_period(pwm),
+		period_ms = DIV_ROUND_UP_ULL(pwm_get_period(pwm),
 					 NSEC_PER_MSEC);
 		msleep(period_ms);
 
@@ -213,6 +213,45 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
 	}
 }
 
+static int pwm_imx27_calc_period_cycles(const struct pwm_state *state,
+					unsigned long clk_rate,
+					unsigned long *period_cycles)
+{
+	u64 c = 0, c1, c2;
+
+	c1 = clk_rate;
+	c2 = state->period;
+	if (c2 > c1) {
+		c2 = c1;
+		c1 = state->period;
+	}
+
+	if (!c1 || !c2) {
+		pr_err("clk rate and period should be nonzero\n");
+		return -EINVAL;
+	}
+
+	if (c2 <= div64_u64(U64_MAX, c1)) {
+		c = c1 * c2;
+		do_div(c, 1000000000);
+	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000))) {
+		do_div(c1, 1000);
+		c = c1 * c2;
+		do_div(c, 1000000);
+	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000))) {
+		do_div(c1, 1000000);
+		c = c1 * c2;
+		do_div(c, 1000);
+	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000000))) {
+		do_div(c1, 1000000000);
+		c = c1 * c2;
+	}
+
+	*period_cycles = c;
+
+	return 0;
+}
+
 static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			   const struct pwm_state *state)
 {
@@ -225,18 +264,16 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	pwm_get_state(pwm, &cstate);
 
-	c = clk_get_rate(imx->clk_per);
-	c *= state->period;
-
-	do_div(c, 1000000000);
-	period_cycles = c;
+	ret = pwm_imx27_calc_period_cycles(state, clk_get_rate(imx->clk_per),
+					   &period_cycles);
+	if (ret)
+		return ret;
 
 	prescale = period_cycles / 0x10000 + 1;
 
 	period_cycles /= prescale;
 	c = (unsigned long long)period_cycles * state->duty_cycle;
-	do_div(c, state->period);
-	duty_cycles = c;
+	duty_cycles = div64_u64(c, state->period);
 
 	/*
 	 * according to imx pwm RM, the real period value should be PERIOD
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 07/11] pwm: sifive: Use 64-bit division macro

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by using DIV64_U64_ROUND_CLOSEST to
handle a 64-bit divisor.

Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: linux-riscv@lists.infradead.org
Cc: Yash Shah <yash.shah@sifive.com>
Cc: Atish Patra <atish.patra@wdc.com>

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Acked-by: Palmer Dabbelt <palmerdabbelt@google.com>
---
 drivers/pwm/pwm-sifive.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index cc63f9b..62de0bb 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -181,7 +181,7 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	 * consecutively
 	 */
 	num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
-	frac = DIV_ROUND_CLOSEST_ULL(num, state->period);
+	frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
 	/* The hardware cannot generate a 100% duty cycle */
 	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 08/11] pwm: sun4i: Use nsecs_to_jiffies to avoid a division

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.period's datatype
to u64, prepare for this transition by using nsecs_to_jiffies() which
does away with the need for a division operation.

Cc: Maxime Ripard <mripard@kernel.org>
Cc: Chen-Yu Tsai <wens@csie.org>
Cc: Philipp Zabel <p.zabel@pengutronix.de>

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/pwm/pwm-sun4i.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 5c677c5..1694e69 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -285,7 +285,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
 	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
 	sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
-		usecs_to_jiffies(cstate.period / 1000 + 1);
+		nsecs_to_jiffies(cstate.period + 1000);
 
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 09/11] backlight: pwm_bl: Use 64-bit division function

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_state.period's datatype
to u64, prepare for this transition by using div_u64 to handle a 64-bit
dividend instead of a straight division operation.

Cc: Lee Jones <lee.jones@linaro.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: Jingoo Han <jingoohan1@gmail.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: linux-pwm@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
---
 drivers/video/backlight/pwm_bl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index efb4efc..3e5dbcf 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -625,7 +625,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 		pb->scale = data->max_brightness;
 	}
 
-	pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
+	pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
+				pb->scale));
 
 	props.type = BACKLIGHT_RAW;
 	props.max_brightness = data->max_brightness;
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 10/11] clk: pwm: Use 64-bit division function

[Guru Das Srinagesh]

Since the PWM framework is switching struct pwm_args.period's datatype
to u64, prepare for this transition by using div64_u64 to handle a
64-bit divisor.

Also ensure that divide-by-zero (with fixed_rate as denominator) does
not happen with an explicit check with probe failure as a consequence.

Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: linux-clk@vger.kernel.org

Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/clk/clk-pwm.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
index 87fe0b0e..86f2e2d 100644
--- a/drivers/clk/clk-pwm.c
+++ b/drivers/clk/clk-pwm.c
@@ -89,7 +89,12 @@ static int clk_pwm_probe(struct platform_device *pdev)
 	}
 
 	if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
-		clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
+		clk_pwm->fixed_rate = div64_u64(NSEC_PER_SEC, pargs.period);
+
+	if (!clk_pwm->fixed_rate) {
+		dev_err(&pdev->dev, "fixed_rate cannot be zero\n");
+		return -EINVAL;
+	}
 
 	if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
 	    pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

[PATCH v12 11/11] pwm: core: Convert period and duty cycle to u64

[Guru Das Srinagesh]

Because period and duty cycle are defined as ints with units of
nanoseconds, the maximum time duration that can be set is limited to
~2.147 seconds. Change their definitions to u64 in the structs of the
PWM framework so that higher durations may be set.

Also use the right format specifiers in debug prints in both core.c as
well as pwm-stm32-lp.c.

Cc: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Joe Perches <joe@perches.com>

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
---
 drivers/pwm/core.c         | 14 +++++++-------
 drivers/pwm/pwm-stm32-lp.c |  2 +-
 drivers/pwm/sysfs.c        |  8 ++++----
 include/linux/pwm.h        | 12 ++++++------
 4 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 9973c44..b6c5f9f 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -510,12 +510,12 @@ static void pwm_apply_state_debug(struct pwm_device *pwm,
 	    last->period > s2.period &&
 	    last->period <= state->period)
 		dev_warn(chip->dev,
-			 ".apply didn't pick the best available period (requested: %u, applied: %u, possible: %u)\n",
+			 ".apply didn't pick the best available period (requested: %llu, applied: %llu, possible: %llu)\n",
 			 state->period, s2.period, last->period);
 
 	if (state->enabled && state->period < s2.period)
 		dev_warn(chip->dev,
-			 ".apply is supposed to round down period (requested: %u, applied: %u)\n",
+			 ".apply is supposed to round down period (requested: %llu, applied: %llu)\n",
 			 state->period, s2.period);
 
 	if (state->enabled &&
@@ -524,14 +524,14 @@ static void pwm_apply_state_debug(struct pwm_device *pwm,
 	    last->duty_cycle > s2.duty_cycle &&
 	    last->duty_cycle <= state->duty_cycle)
 		dev_warn(chip->dev,
-			 ".apply didn't pick the best available duty cycle (requested: %u/%u, applied: %u/%u, possible: %u/%u)\n",
+			 ".apply didn't pick the best available duty cycle (requested: %llu/%llu, applied: %llu/%llu, possible: %llu/%llu)\n",
 			 state->duty_cycle, state->period,
 			 s2.duty_cycle, s2.period,
 			 last->duty_cycle, last->period);
 
 	if (state->enabled && state->duty_cycle < s2.duty_cycle)
 		dev_warn(chip->dev,
-			 ".apply is supposed to round down duty_cycle (requested: %u/%u, applied: %u/%u)\n",
+			 ".apply is supposed to round down duty_cycle (requested: %llu/%llu, applied: %llu/%llu)\n",
 			 state->duty_cycle, state->period,
 			 s2.duty_cycle, s2.period);
 
@@ -558,7 +558,7 @@ static void pwm_apply_state_debug(struct pwm_device *pwm,
 	    (s1.enabled && s1.period != last->period) ||
 	    (s1.enabled && s1.duty_cycle != last->duty_cycle)) {
 		dev_err(chip->dev,
-			".apply is not idempotent (ena=%d pol=%d %u/%u) -> (ena=%d pol=%d %u/%u)\n",
+			".apply is not idempotent (ena=%d pol=%d %llu/%llu) -> (ena=%d pol=%d %llu/%llu)\n",
 			s1.enabled, s1.polarity, s1.duty_cycle, s1.period,
 			last->enabled, last->polarity, last->duty_cycle,
 			last->period);
@@ -1284,8 +1284,8 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
 		if (state.enabled)
 			seq_puts(s, " enabled");
 
-		seq_printf(s, " period: %u ns", state.period);
-		seq_printf(s, " duty: %u ns", state.duty_cycle);
+		seq_printf(s, " period: %llu ns", state.period);
+		seq_printf(s, " duty: %llu ns", state.duty_cycle);
 		seq_printf(s, " polarity: %s",
 			   state.polarity ? "inverse" : "normal");
 
diff --git a/drivers/pwm/pwm-stm32-lp.c b/drivers/pwm/pwm-stm32-lp.c
index 67fca62..134c146 100644
--- a/drivers/pwm/pwm-stm32-lp.c
+++ b/drivers/pwm/pwm-stm32-lp.c
@@ -61,7 +61,7 @@ static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	do_div(div, NSEC_PER_SEC);
 	if (!div) {
 		/* Clock is too slow to achieve requested period. */
-		dev_dbg(priv->chip.dev, "Can't reach %u ns\n",	state->period);
+		dev_dbg(priv->chip.dev, "Can't reach %llu ns\n", state->period);
 		return -EINVAL;
 	}
 
diff --git a/drivers/pwm/sysfs.c b/drivers/pwm/sysfs.c
index 2389b86..449dbc0 100644
--- a/drivers/pwm/sysfs.c
+++ b/drivers/pwm/sysfs.c
@@ -42,7 +42,7 @@ static ssize_t period_show(struct device *child,
 
 	pwm_get_state(pwm, &state);
 
-	return sprintf(buf, "%u\n", state.period);
+	return sprintf(buf, "%llu\n", state.period);
 }
 
 static ssize_t period_store(struct device *child,
@@ -52,10 +52,10 @@ static ssize_t period_store(struct device *child,
 	struct pwm_export *export = child_to_pwm_export(child);
 	struct pwm_device *pwm = export->pwm;
 	struct pwm_state state;
-	unsigned int val;
+	u64 val;
 	int ret;
 
-	ret = kstrtouint(buf, 0, &val);
+	ret = kstrtou64(buf, 0, &val);
 	if (ret)
 		return ret;
 
@@ -77,7 +77,7 @@ static ssize_t duty_cycle_show(struct device *child,
 
 	pwm_get_state(pwm, &state);
 
-	return sprintf(buf, "%u\n", state.duty_cycle);
+	return sprintf(buf, "%llu\n", state.duty_cycle);
 }
 
 static ssize_t duty_cycle_store(struct device *child,
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 2635b2a..a13ff38 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -39,7 +39,7 @@ enum pwm_polarity {
  * current PWM hardware state.
  */
 struct pwm_args {
-	unsigned int period;
+	u64 period;
 	enum pwm_polarity polarity;
 };
 
@@ -56,8 +56,8 @@ enum {
  * @enabled: PWM enabled status
  */
 struct pwm_state {
-	unsigned int period;
-	unsigned int duty_cycle;
+	u64 period;
+	u64 duty_cycle;
 	enum pwm_polarity polarity;
 	bool enabled;
 };
@@ -107,13 +107,13 @@ static inline bool pwm_is_enabled(const struct pwm_device *pwm)
 	return state.enabled;
 }
 
-static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
+static inline void pwm_set_period(struct pwm_device *pwm, u64 period)
 {
 	if (pwm)
 		pwm->state.period = period;
 }
 
-static inline unsigned int pwm_get_period(const struct pwm_device *pwm)
+static inline u64 pwm_get_period(const struct pwm_device *pwm)
 {
 	struct pwm_state state;
 
@@ -128,7 +128,7 @@ static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
 		pwm->state.duty_cycle = duty;
 }
 
-static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
+static inline u64 pwm_get_duty_cycle(const struct pwm_device *pwm)
 {
 	struct pwm_state state;
 
-- 
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [PATCH v12 10/11] clk: pwm: Use 64-bit division function

[Guru Das Srinagesh]

+ Arnd, David

On Wed, Apr 08, 2020 at 11:52:39PM -0700, Guru Das Srinagesh wrote:
> Since the PWM framework is switching struct pwm_args.period's datatype
> to u64, prepare for this transition by using div64_u64 to handle a
> 64-bit divisor.
> 
> Also ensure that divide-by-zero (with fixed_rate as denominator) does
> not happen with an explicit check with probe failure as a consequence.
> 
> Cc: Michael Turquette <mturquette@baylibre.com>
> Cc: Stephen Boyd <sboyd@kernel.org>
> Cc: linux-clk@vger.kernel.org
> 
> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
> ---
>  drivers/clk/clk-pwm.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
> index 87fe0b0e..86f2e2d 100644
> --- a/drivers/clk/clk-pwm.c
> +++ b/drivers/clk/clk-pwm.c
> @@ -89,7 +89,12 @@ static int clk_pwm_probe(struct platform_device *pdev)
>  	}
>  
>  	if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
> -		clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
> +		clk_pwm->fixed_rate = div64_u64(NSEC_PER_SEC, pargs.period);
> +
> +	if (!clk_pwm->fixed_rate) {
> +		dev_err(&pdev->dev, "fixed_rate cannot be zero\n");
> +		return -EINVAL;
> +	}
>  
>  	if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
>  	    pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
> -- 

Hello Arnd, David:

Sorry, missed cc-ing you both to this patch while sending it out. Could
you please review it when you get a chance to?

Thank you.

Guru Das.

Re: [PATCH v12 06/11] pwm: imx27: Use 64-bit division macro and function

[Guru Das Srinagesh]

On Wed, Apr 08, 2020 at 11:52:35PM -0700, Guru Das Srinagesh wrote:
> Since the PWM framework is switching struct pwm_state.period's
> datatype to u64, prepare for this transition by using
> DIV_ROUND_UP_ULL to handle a 64-bit dividend, and div64_u64 to handle a
> 64-bit divisor.
> 
> Also handle a possible overflow in the calculation of period_cycles when
> both clk_rate and period are large numbers. This logic was unit-tested
> out by calculating period_cycles using both the existing logic and the
> proposed one, and the results are as below.
> 
> ----------------------------------------------------------------------------
>  clk_rate            period           existing            proposed
> ----------------------------------------------------------------------------
> 1000000000   18446744073709551615    18446744072    18446744073000000000
>                    (U64_MAX)
> ----------------------------------------------------------------------------
> 1000000000        4294967291         4294967291         4294967291
> ----------------------------------------------------------------------------
> 
> Overflow occurs in the first case with the existing logic, whereas the
> proposed logic handles it better, sacrificing some precision in a best-effort
> attempt to handle overflow. As for the second case where there are
> more typical values of period, the proposed logic handles that correctly
> too.
> 
> Cc: Shawn Guo <shawnguo@kernel.org>
> Cc: Sascha Hauer <s.hauer@pengutronix.de>
> Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
> Cc: Fabio Estevam <festevam@gmail.com>
> Cc: NXP Linux Team <linux-imx@nxp.com>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Cc: David Collins <collinsd@codeaurora.org>
> 
> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
> ---
>  drivers/pwm/pwm-imx27.c | 53 +++++++++++++++++++++++++++++++++++++++++--------
>  1 file changed, 45 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
> index a6e40d4..164cb65 100644
> --- a/drivers/pwm/pwm-imx27.c
> +++ b/drivers/pwm/pwm-imx27.c
> @@ -203,7 +203,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
>  	sr = readl(imx->mmio_base + MX3_PWMSR);
>  	fifoav = FIELD_GET(MX3_PWMSR_FIFOAV, sr);
>  	if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
> -		period_ms = DIV_ROUND_UP(pwm_get_period(pwm),
> +		period_ms = DIV_ROUND_UP_ULL(pwm_get_period(pwm),
>  					 NSEC_PER_MSEC);
>  		msleep(period_ms);
>  
> @@ -213,6 +213,45 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
>  	}
>  }
>  
> +static int pwm_imx27_calc_period_cycles(const struct pwm_state *state,
> +					unsigned long clk_rate,
> +					unsigned long *period_cycles)
> +{
> +	u64 c = 0, c1, c2;
> +
> +	c1 = clk_rate;
> +	c2 = state->period;
> +	if (c2 > c1) {
> +		c2 = c1;
> +		c1 = state->period;
> +	}
> +
> +	if (!c1 || !c2) {
> +		pr_err("clk rate and period should be nonzero\n");
> +		return -EINVAL;
> +	}
> +
> +	if (c2 <= div64_u64(U64_MAX, c1)) {
> +		c = c1 * c2;
> +		do_div(c, 1000000000);
> +	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000))) {
> +		do_div(c1, 1000);
> +		c = c1 * c2;
> +		do_div(c, 1000000);
> +	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000))) {
> +		do_div(c1, 1000000);
> +		c = c1 * c2;
> +		do_div(c, 1000);
> +	} else if (c2 <= div64_u64(U64_MAX, div64_u64(c1, 1000000000))) {
> +		do_div(c1, 1000000000);
> +		c = c1 * c2;
> +	}
> +
> +	*period_cycles = c;
> +
> +	return 0;
> +}
> +
>  static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  			   const struct pwm_state *state)
>  {
> @@ -225,18 +264,16 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  
>  	pwm_get_state(pwm, &cstate);
>  
> -	c = clk_get_rate(imx->clk_per);
> -	c *= state->period;
> -
> -	do_div(c, 1000000000);
> -	period_cycles = c;
> +	ret = pwm_imx27_calc_period_cycles(state, clk_get_rate(imx->clk_per),
> +					   &period_cycles);
> +	if (ret)
> +		return ret;
>  
>  	prescale = period_cycles / 0x10000 + 1;
>  
>  	period_cycles /= prescale;
>  	c = (unsigned long long)period_cycles * state->duty_cycle;
> -	do_div(c, state->period);
> -	duty_cycles = c;
> +	duty_cycles = div64_u64(c, state->period);
>  
>  	/*
>  	 * according to imx pwm RM, the real period value should be PERIOD
> -- 

Hi Arnd,

Missed cc-ing you to this patch when sending it out. Could you please
review this when you get a chance to?

Thank you.

Guru Das.

Re: [PATCH v12 08/11] pwm: sun4i: Use nsecs_to_jiffies to avoid a division

[Guru Das Srinagesh]

On Wed, Apr 08, 2020 at 11:52:37PM -0700, Guru Das Srinagesh wrote:
> Since the PWM framework is switching struct pwm_state.period's datatype
> to u64, prepare for this transition by using nsecs_to_jiffies() which
> does away with the need for a division operation.
> 
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Chen-Yu Tsai <wens@csie.org>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> 
> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
> ---
>  drivers/pwm/pwm-sun4i.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
> index 5c677c5..1694e69 100644
> --- a/drivers/pwm/pwm-sun4i.c
> +++ b/drivers/pwm/pwm-sun4i.c
> @@ -285,7 +285,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  	val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
>  	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
>  	sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
> -		usecs_to_jiffies(cstate.period / 1000 + 1);
> +		nsecs_to_jiffies(cstate.period + 1000);
>  
>  	if (state->polarity != PWM_POLARITY_NORMAL)
>  		ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
> -- 

Hi Chen-Yu,

You had provided your "Acked-by:" [1] for an earlier version of this
patch but now that I've revised the patch based on a review comment I
received [2], could you please review this patch once again?

Thank you.

Guru Das.

[1] https://www.spinics.net/lists/linux-pwm/msg11755.html
[2] https://www.spinics.net/lists/linux-pwm/msg11956.html

Re: [PATCH v12 08/11] pwm: sun4i: Use nsecs_to_jiffies to avoid a division

[Chen-Yu Tsai]

On Thu, Apr 9, 2020 at 2:53 PM Guru Das Srinagesh <gurus@codeaurora.org> wrote:
>
> Since the PWM framework is switching struct pwm_state.period's datatype
> to u64, prepare for this transition by using nsecs_to_jiffies() which
> does away with the need for a division operation.
>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Chen-Yu Tsai <wens@csie.org>
> Cc: Philipp Zabel <p.zabel@pengutronix.de>
>
> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>

Acked-by: Chen-Yu Tsai <wens@csie.org>

Re: [PATCH v12 09/11] backlight: pwm_bl: Use 64-bit division function

[Lee Jones]

On Wed, 08 Apr 2020, Guru Das Srinagesh wrote:

> Since the PWM framework is switching struct pwm_state.period's datatype
> to u64, prepare for this transition by using div_u64 to handle a 64-bit
> dividend instead of a straight division operation.
> 
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Daniel Thompson <daniel.thompson@linaro.org>
> Cc: Jingoo Han <jingoohan1@gmail.com>
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Cc: linux-pwm@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Cc: linux-fbdev@vger.kernel.org
> 
> Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> ---
>  drivers/video/backlight/pwm_bl.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

I see that this is part of a large set, but the remainder of the
patches have been hidden from me.

Does this mean I can apply this patch on its own?

> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index efb4efc..3e5dbcf 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -625,7 +625,8 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>  		pb->scale = data->max_brightness;
>  	}
>  
> -	pb->lth_brightness = data->lth_brightness * (state.period / pb->scale);
> +	pb->lth_brightness = data->lth_brightness * (div_u64(state.period,
> +				pb->scale));
>  
>  	props.type = BACKLIGHT_RAW;
>  	props.max_brightness = data->max_brightness;

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog

Re: [PATCH v12 09/11] backlight: pwm_bl: Use 64-bit division function

[Guru Das Srinagesh]

On Thu, Apr 16, 2020 at 10:44:20AM +0100, Lee Jones wrote:
> On Wed, 08 Apr 2020, Guru Das Srinagesh wrote:
> 
> > Since the PWM framework is switching struct pwm_state.period's datatype
> > to u64, prepare for this transition by using div_u64 to handle a 64-bit
> > dividend instead of a straight division operation.
> > 
> > Cc: Lee Jones <lee.jones@linaro.org>
> > Cc: Daniel Thompson <daniel.thompson@linaro.org>
> > Cc: Jingoo Han <jingoohan1@gmail.com>
> > Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> > Cc: linux-pwm@vger.kernel.org
> > Cc: dri-devel@lists.freedesktop.org
> > Cc: linux-fbdev@vger.kernel.org
> > 
> > Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>
> > Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
> > ---
> >  drivers/video/backlight/pwm_bl.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> I see that this is part of a large set, but the remainder of the
> patches have been hidden from me.

Sorry about that, the full series is here: [1].

> Does this mean I can apply this patch on its own?

I'll defer to Uwe on this point as I am not sure of the implications of
taking in this single patch and not the entire series.

Thank you.

Guru Das.

[1] https://www.spinics.net/lists/linux-pwm/msg12131.html