video: da8xx-fb: reset LCDC only if functional clock changes with DVFS

Started by Manjunathappa, Prakash on Dec 21, 2011 · 3 messages from 2 authors · Last reply Dec 21, 2011

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STALE5442d

Manjunathappa, Prakash Dec 21, 07:39 #

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LCDC functional clock may or may not be derived from CPU/MPU DPLL,
For example,
AM335x => Separate independent DPLL for LCDC
Davinci => Same DPLL as MPU

So, on platforms where LCDC functional clock is not derived from CPU/MPU
PLL it is not required to reset LCDC module, if CPU frequency does not
change with DVFS.

This patch adds check to do reset only if functional clock changes
between pre and post notifier callbacks with DVFS.

Signed-off-by: Manjunathappa, Prakash <redacted>
---
 drivers/video/da8xx-fb.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/video/da8xx-fb.c b/drivers/video/da8xx-fb.c
index 29577bf..1334a68 100644
--- a/drivers/video/da8xx-fb.c
+++ b/drivers/video/da8xx-fb.c

@@ -161,6 +161,7 @@ struct da8xx_fb_par {
 	int			vsync_timeout;
 #ifdef CONFIG_CPU_FREQ
 	struct notifier_block	freq_transition;
+	unsigned int		lcd_fck_rate;
 #endif
 	void (*panel_power_ctrl)(int);
 };

@@ -840,11 +841,12 @@ static int lcd_da8xx_cpufreq_transition(struct notifier_block *nb,
 	struct da8xx_fb_par *par;
 
 	par = container_of(nb, struct da8xx_fb_par, freq_transition);
-	if (val = CPUFREQ_PRECHANGE) {
-		lcd_disable_raster();
-	} else if (val = CPUFREQ_POSTCHANGE) {
-		lcd_calc_clk_divider(par);
-		lcd_enable_raster();
+	if (val = CPUFREQ_POSTCHANGE) {
+		if (par->lcd_fck_rate != clk_get_rate(par->lcdc_clk)) {
+			lcd_disable_raster();
+			lcd_calc_clk_divider(par);
+			lcd_enable_raster();
+		}
 	}
 
 	return 0;

@@ -1137,6 +1139,7 @@ static int __devinit fb_probe(struct platform_device *device)
 
 	par = da8xx_fb_info->par;
 	par->lcdc_clk = fb_clk;
+	par->lcd_fck_rate = clk_get_rate(fb_clk);
 	par->pxl_clk = lcdc_info->pxl_clk;
 	if (fb_pdata->panel_power_ctrl) {
 		par->panel_power_ctrl = fb_pdata->panel_power_ctrl;

-- 
1.7.1

Re: [PATCH] video: da8xx-fb: reset LCDC only if functional clock

Madhvapathi Sriram replied to Manjunathappa, Prakash Dec 21, 10:59 #

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Prakash,

On Wed, Dec 21, 2011 at 12:57 PM, Manjunathappa, Prakash
[off-list ref] wrote:

LCDC functional clock may or may not be derived from CPU/MPU DPLL,
For example,
AM335x => Separate independent DPLL for LCDC
Davinci => Same DPLL as MPU

So, on platforms where LCDC functional clock is not derived from CPU/MPU
PLL it is not required to reset LCDC module, if CPU frequency does not
change with DVFS.

Is it not the case that the CPU frequency always changes during DVFS?
This sentence does not strike me straight.
Did you mean that if the frequency of the PLL (from which LCDC
derives) does not change with DVFS, then LCDC module is not required
to be reset?

quoted hunk

This patch adds check to do reset only if functional clock changes
between pre and post notifier callbacks with DVFS.

Signed-off-by: Manjunathappa, Prakash <redacted>
---
 drivers/video/da8xx-fb.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/video/da8xx-fb.c b/drivers/video/da8xx-fb.c
index 29577bf..1334a68 100644
--- a/drivers/video/da8xx-fb.c
+++ b/drivers/video/da8xx-fb.c

@@ -161,6 +161,7 @@ struct da8xx_fb_par {

       int                     vsync_timeout;
 #ifdef CONFIG_CPU_FREQ
       struct notifier_block   freq_transition;
+       unsigned int            lcd_fck_rate;
 #endif
       void (*panel_power_ctrl)(int);
 };

@@ -840,11 +841,12 @@ static int lcd_da8xx_cpufreq_transition(struct notifier_block *nb,

       struct da8xx_fb_par *par;

       par = container_of(nb, struct da8xx_fb_par, freq_transition);
-       if (val = CPUFREQ_PRECHANGE) {
-               lcd_disable_raster();
-       } else if (val = CPUFREQ_POSTCHANGE) {
-               lcd_calc_clk_divider(par);
-               lcd_enable_raster();
+       if (val = CPUFREQ_POSTCHANGE) {
+               if (par->lcd_fck_rate != clk_get_rate(par->lcdc_clk)) {
+                       lcd_disable_raster();
+                       lcd_calc_clk_divider(par);
+                       lcd_enable_raster();
+               }
       }

       return 0;

@@ -1137,6 +1139,7 @@ static int __devinit fb_probe(struct platform_device *device)

14 more quoted lines

RE: [PATCH] video: da8xx-fb: reset LCDC only if functional clock

Manjunathappa, Prakash replied to Manjunathappa, Prakash Dec 21, 11:11 #

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Hi Sriram,

On Wed, Dec 21, 2011 at 16:17:01, Madhvapathi Sriram wrote:

Prakash,

On Wed, Dec 21, 2011 at 12:57 PM, Manjunathappa, Prakash
[off-list ref] wrote:

quoted

LCDC functional clock may or may not be derived from CPU/MPU DPLL,
For example,
AM335x => Separate independent DPLL for LCDC
Davinci => Same DPLL as MPU

So, on platforms where LCDC functional clock is not derived from CPU/MPU
PLL it is not required to reset LCDC module, if CPU frequency does not
change with DVFS.

Is it not the case that the CPU frequency always changes during DVFS?
This sentence does not strike me straight.
Did you mean that if the frequency of the PLL (from which LCDC
derives) does not change with DVFS, then LCDC module is not required
to be reset?

Ok I will re-phrase it as below:
So, on platforms where LCDC functional clock is not derived from CPU/MPU
PLL it is not required to reset LCDC module as its functional clock does not change with DVFS.

quoted

This patch adds check to do reset only if functional clock changes
between pre and post notifier callbacks with DVFS.

Signed-off-by: Manjunathappa, Prakash <redacted>
---
 drivers/video/da8xx-fb.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/video/da8xx-fb.c b/drivers/video/da8xx-fb.c
index 29577bf..1334a68 100644
--- a/drivers/video/da8xx-fb.c
+++ b/drivers/video/da8xx-fb.c

@@ -161,6 +161,7 @@ struct da8xx_fb_par {

       int                     vsync_timeout;
 #ifdef CONFIG_CPU_FREQ
       struct notifier_block   freq_transition;
+       unsigned int            lcd_fck_rate;
 #endif
       void (*panel_power_ctrl)(int);
 };

@@ -840,11 +841,12 @@ static int lcd_da8xx_cpufreq_transition(struct notifier_block *nb,

       struct da8xx_fb_par *par;

       par = container_of(nb, struct da8xx_fb_par, freq_transition);
-       if (val = CPUFREQ_PRECHANGE) {
-               lcd_disable_raster();
-       } else if (val = CPUFREQ_POSTCHANGE) {
-               lcd_calc_clk_divider(par);
-               lcd_enable_raster();
+       if (val = CPUFREQ_POSTCHANGE) {
+               if (par->lcd_fck_rate != clk_get_rate(par->lcdc_clk)) {
+                       lcd_disable_raster();
+                       lcd_calc_clk_divider(par);
+                       lcd_enable_raster();
+               }
       }

       return 0;

@@ -1137,6 +1139,7 @@ static int __devinit fb_probe(struct platform_device *device)

15 more quoted lines

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