[PATCH] drm/tilcdc: Fix setting clock divider for omap-l138

[PATCH] drm/tilcdc: Fix setting clock divider for omap-l138

[David Lechner]

This fixes setting the clock divider on the TI OMAP-L138 LCDK board.

The clock drivers for OMAP-L138 are being covernted to the common clock
framework. When this happens, clk_set_rate() will no longer return an
error. However, on this SoC, the clock rate cannot actually be changed
because the clock has to maintain a fixed ratio to the ARM clock. So
after attempting to set the clock rate, we need to check to see if the
new rate is actually close enough. If not, then follow the previous
error path to adjust the divider in LCDC IP block to compensate for not
being able to change the parent clock rate.

Tested working on a TI OMAP-L138 LCDK board.

Signed-off-by: David Lechner <david@lechnology.com>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 8bf6bb9..6931777 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -224,7 +224,7 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
 
 	ret = clk_set_rate(priv->clk, req_rate * clkdiv);
 	clk_rate = clk_get_rate(priv->clk);
-	if (ret < 0) {
+	if (ret < 0 || tilcdc_pclk_diff(req_rate, clk_rate) > 5) {
 		/*
 		 * If we fail to set the clock rate (some architectures don't
 		 * use the common clock framework yet and may not implement
-- 
2.7.4

Re: [PATCH] drm/tilcdc: Fix setting clock divider for omap-l138

[Jyri Sarha]

Thanks,
I'll pick this for v4.18.

Best regards,
Jyri

On 15/03/18 00:58, David Lechner wrote:
> This fixes setting the clock divider on the TI OMAP-L138 LCDK board.
> 
> The clock drivers for OMAP-L138 are being covernted to the common clock
> framework. When this happens, clk_set_rate() will no longer return an
> error. However, on this SoC, the clock rate cannot actually be changed
> because the clock has to maintain a fixed ratio to the ARM clock. So
> after attempting to set the clock rate, we need to check to see if the
> new rate is actually close enough. If not, then follow the previous
> error path to adjust the divider in LCDC IP block to compensate for not
> being able to change the parent clock rate.
> 
> Tested working on a TI OMAP-L138 LCDK board.
> 
> Signed-off-by: David Lechner <david@lechnology.com>
> ---
>  drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> index 8bf6bb9..6931777 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -224,7 +224,7 @@ static void tilcdc_crtc_set_clk(struct drm_crtc *crtc)
>  
>  	ret = clk_set_rate(priv->clk, req_rate * clkdiv);
>  	clk_rate = clk_get_rate(priv->clk);
> -	if (ret < 0) {
> +	if (ret < 0 || tilcdc_pclk_diff(req_rate, clk_rate) > 5) {
>  		/*
>  		 * If we fail to set the clock rate (some architectures don't
>  		 * use the common clock framework yet and may not implement
> 


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Re: [PATCH] drm/tilcdc: Fix setting clock divider for omap-l138

[David Lechner]

On 03/19/2018 04:05 AM, Jyri Sarha wrote:
> Thanks,
> I'll pick this for v4.18.

Ping. I don't see this in drm-misc-next yet.

Re: [PATCH] drm/tilcdc: Fix setting clock divider for omap-l138

[Jyri Sarha]

On 05/09/18 19:22, David Lechner wrote:
> On 03/19/2018 04:05 AM, Jyri Sarha wrote:
>> Thanks,
>> I'll pick this for v4.18.
> 
> Ping. I don't see this in drm-misc-next yet.
> 

Thanks for the ping. I thought I would have time to do something more
for tilcdc in v4.18, but it seems I have not. After testing I just sent
a tilcdc pull request with just this patch.

Best regards,
Jyri


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Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki