* [PATCH v1] pwm: mediatek: improve precision in rate calculation
@ 2018-03-02 8:49 ` sean.wang
0 siblings, 0 replies; 5+ messages in thread
From: sean.wang @ 2018-03-02 8:49 UTC (permalink / raw)
To: thierry.reding, matthias.bgg
Cc: linux-pwm, linux-arm-kernel, linux-mediatek, linux-kernel,
Sean Wang, stable
From: Sean Wang <sean.wang@mediatek.com>
Add a way that turning resolution from in nanosecond into in picosecond
to improve noticeably almost 4.5% precision.
It's necessary to hold the new resolution with type u64 and thus related
operations on u64 are applied instead in those rate calculations.
And the patch has a dependency on [1].
[1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
Cc: stable@vger.kernel.org
Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
index 796baea..98b0a93 100644
--- a/drivers/pwm/pwm-mediatek.c
+++ b/drivers/pwm/pwm-mediatek.c
@@ -135,19 +135,25 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
- u32 resolution, clkdiv = 0, reg_width = PWMDWIDTH,
+ u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
reg_thres = PWMTHRES;
+ u64 resolution;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
- resolution = NSEC_PER_SEC / clk_get_rate(clk);
+ /* Using resolution in picosecond gets accuracy higher */
+ resolution = (u64)NSEC_PER_SEC * 1000;
+ do_div(resolution, clk_get_rate(clk));
- while (period_ns / resolution > 8191) {
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
+ while (cnt_period > 8191) {
resolution *= 2;
clkdiv++;
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
+ resolution);
}
if (clkdiv > PWM_CLK_DIV_MAX) {
@@ -165,9 +171,10 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
reg_thres = PWM45THRES_FIXUP;
}
+ cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_width, period_ns / resolution);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, duty_ns / resolution);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
mtk_pwm_clk_disable(chip, pwm);
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v1] pwm: mediatek: improve precision in rate calculation
@ 2018-03-02 8:49 ` sean.wang
0 siblings, 0 replies; 5+ messages in thread
From: sean.wang @ 2018-03-02 8:49 UTC (permalink / raw)
To: thierry.reding, matthias.bgg
Cc: linux-pwm, linux-arm-kernel, linux-mediatek, linux-kernel,
Sean Wang, stable
From: Sean Wang <sean.wang@mediatek.com>
Add a way that turning resolution from in nanosecond into in picosecond
to improve noticeably almost 4.5% precision.
It's necessary to hold the new resolution with type u64 and thus related
operations on u64 are applied instead in those rate calculations.
And the patch has a dependency on [1].
[1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
Cc: stable@vger.kernel.org
Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
index 796baea..98b0a93 100644
--- a/drivers/pwm/pwm-mediatek.c
+++ b/drivers/pwm/pwm-mediatek.c
@@ -135,19 +135,25 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
- u32 resolution, clkdiv = 0, reg_width = PWMDWIDTH,
+ u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
reg_thres = PWMTHRES;
+ u64 resolution;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
- resolution = NSEC_PER_SEC / clk_get_rate(clk);
+ /* Using resolution in picosecond gets accuracy higher */
+ resolution = (u64)NSEC_PER_SEC * 1000;
+ do_div(resolution, clk_get_rate(clk));
- while (period_ns / resolution > 8191) {
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
+ while (cnt_period > 8191) {
resolution *= 2;
clkdiv++;
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
+ resolution);
}
if (clkdiv > PWM_CLK_DIV_MAX) {
@@ -165,9 +171,10 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
reg_thres = PWM45THRES_FIXUP;
}
+ cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_width, period_ns / resolution);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, duty_ns / resolution);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
mtk_pwm_clk_disable(chip, pwm);
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH v1] pwm: mediatek: improve precision in rate calculation
@ 2018-03-02 8:49 ` sean.wang
0 siblings, 0 replies; 5+ messages in thread
From: sean.wang at mediatek.com @ 2018-03-02 8:49 UTC (permalink / raw)
To: linux-arm-kernel
From: Sean Wang <sean.wang@mediatek.com>
Add a way that turning resolution from in nanosecond into in picosecond
to improve noticeably almost 4.5% precision.
It's necessary to hold the new resolution with type u64 and thus related
operations on u64 are applied instead in those rate calculations.
And the patch has a dependency on [1].
[1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
Cc: stable at vger.kernel.org
Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
Signed-off-by: Sean Wang <sean.wang@mediatek.com>
---
drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
1 file changed, 12 insertions(+), 5 deletions(-)
diff --git a/drivers/pwm/pwm-mediatek.c b/drivers/pwm/pwm-mediatek.c
index 796baea..98b0a93 100644
--- a/drivers/pwm/pwm-mediatek.c
+++ b/drivers/pwm/pwm-mediatek.c
@@ -135,19 +135,25 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
{
struct mtk_pwm_chip *pc = to_mtk_pwm_chip(chip);
struct clk *clk = pc->clks[MTK_CLK_PWM1 + pwm->hwpwm];
- u32 resolution, clkdiv = 0, reg_width = PWMDWIDTH,
+ u32 clkdiv = 0, cnt_period, cnt_duty, reg_width = PWMDWIDTH,
reg_thres = PWMTHRES;
+ u64 resolution;
int ret;
ret = mtk_pwm_clk_enable(chip, pwm);
if (ret < 0)
return ret;
- resolution = NSEC_PER_SEC / clk_get_rate(clk);
+ /* Using resolution in picosecond gets accuracy higher */
+ resolution = (u64)NSEC_PER_SEC * 1000;
+ do_div(resolution, clk_get_rate(clk));
- while (period_ns / resolution > 8191) {
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000, resolution);
+ while (cnt_period > 8191) {
resolution *= 2;
clkdiv++;
+ cnt_period = DIV_ROUND_CLOSEST_ULL((u64)period_ns * 1000,
+ resolution);
}
if (clkdiv > PWM_CLK_DIV_MAX) {
@@ -165,9 +171,10 @@ static int mtk_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
reg_thres = PWM45THRES_FIXUP;
}
+ cnt_duty = DIV_ROUND_CLOSEST_ULL((u64)duty_ns * 1000, resolution);
mtk_pwm_writel(pc, pwm->hwpwm, PWMCON, BIT(15) | clkdiv);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_width, period_ns / resolution);
- mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, duty_ns / resolution);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_width, cnt_period);
+ mtk_pwm_writel(pc, pwm->hwpwm, reg_thres, cnt_duty);
mtk_pwm_clk_disable(chip, pwm);
--
2.7.4
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v1] pwm: mediatek: improve precision in rate calculation
2018-03-02 8:49 ` sean.wang
@ 2018-03-27 22:33 ` Thierry Reding
-1 siblings, 0 replies; 5+ messages in thread
From: Thierry Reding @ 2018-03-27 22:33 UTC (permalink / raw)
To: sean.wang
Cc: matthias.bgg, linux-pwm, linux-arm-kernel, linux-mediatek,
linux-kernel, stable
[-- Attachment #1: Type: text/plain, Size: 814 bytes --]
On Fri, Mar 02, 2018 at 04:49:14PM +0800, sean.wang@mediatek.com wrote:
> From: Sean Wang <sean.wang@mediatek.com>
>
> Add a way that turning resolution from in nanosecond into in picosecond
> to improve noticeably almost 4.5% precision.
>
> It's necessary to hold the new resolution with type u64 and thus related
> operations on u64 are applied instead in those rate calculations.
>
> And the patch has a dependency on [1].
>
> [1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
>
> Cc: stable@vger.kernel.org
> Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> ---
> drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
Applied, thanks.
Thierry
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH v1] pwm: mediatek: improve precision in rate calculation
@ 2018-03-27 22:33 ` Thierry Reding
0 siblings, 0 replies; 5+ messages in thread
From: Thierry Reding @ 2018-03-27 22:33 UTC (permalink / raw)
To: linux-arm-kernel
On Fri, Mar 02, 2018 at 04:49:14PM +0800, sean.wang at mediatek.com wrote:
> From: Sean Wang <sean.wang@mediatek.com>
>
> Add a way that turning resolution from in nanosecond into in picosecond
> to improve noticeably almost 4.5% precision.
>
> It's necessary to hold the new resolution with type u64 and thus related
> operations on u64 are applied instead in those rate calculations.
>
> And the patch has a dependency on [1].
>
> [1] http://lists.infradead.org/pipermail/linux-mediatek/2018-March/012225.html
>
> Cc: stable at vger.kernel.org
> Fixes: caf065f8fd58 ("pwm: Add MediaTek PWM support")
> Signed-off-by: Sean Wang <sean.wang@mediatek.com>
> ---
> drivers/pwm/pwm-mediatek.c | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
Applied, thanks.
Thierry
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://lists.infradead.org/pipermail/linux-arm-kernel/attachments/20180328/f2ff269c/attachment.sig>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-03-27 22:33 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-03-02 8:49 [PATCH v1] pwm: mediatek: improve precision in rate calculation sean.wang
2018-03-02 8:49 ` sean.wang at mediatek.com
2018-03-02 8:49 ` sean.wang
2018-03-27 22:33 ` Thierry Reding
2018-03-27 22:33 ` Thierry Reding
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.