[PATCH] drm: tilcdc: reduce max_width for revision 1

[PATCH] drm: tilcdc: reduce max_width for revision 1

[Bartosz Golaszewski]

While debugging the drm_bridge support for revision 1 I noticed the
driver was selecting the 1024x768 resolution as default from the set
retrieved from EDID. The following patch reduces the max_width for
rev1 in tilcdc.

Bartosz Golaszewski (1):
  drm: tilcdc: reduce max_width for revision 1

 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

-- 
2.9.3

[PATCH] drm: tilcdc: reduce max_width for revision 1

[Bartosz Golaszewski]

It has been determined that the highest resolution supported correctly
by LCDC rev1 is 800x600. Reduce the max_width value for rev1 to 800 in
crtc_max_width().

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.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 dfe3dd0..9081de5 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -683,7 +683,7 @@ int tilcdc_crtc_max_width(struct drm_crtc *crtc)
 	int max_width = 0;
 
 	if (priv->rev == 1)
-		max_width = 1024;
+		max_width = 800;
 	else if (priv->rev == 2)
 		max_width = 2048;
 
-- 
2.9.3

Re: [PATCH] drm: tilcdc: reduce max_width for revision 1

[Jyri Sarha]

On 11/21/16 19:16, Bartosz Golaszewski wrote:
> It has been determined that the highest resolution supported correctly
> by LCDC rev1 is 800x600. Reduce the max_width value for rev1 to 800 in
> crtc_max_width().
> 

I don't think this is the right way to limit the supported video modes.
There is technically there is no such limit, is there?

If memory bandwidth is limiting the functionality of higher resolutions,
you should use "max-bandwidth" tilcdc device-tree property [1].

Cheers,
Jyri

[1] In "Documentation/devicetree/bindings/display/tilcdc/tilcdc.txt":
Optional properties:
 - max-bandwidth: The maximum pixels per second that the memory
   interface / lcd controller combination can sustain



> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.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 dfe3dd0..9081de5 100644
> --- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> +++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
> @@ -683,7 +683,7 @@ int tilcdc_crtc_max_width(struct drm_crtc *crtc)
>  	int max_width = 0;
>  
>  	if (priv->rev == 1)
> -		max_width = 1024;
> +		max_width = 800;
>  	else if (priv->rev == 2)
>  		max_width = 2048;
>  
> 

Re: [PATCH] drm: tilcdc: reduce max_width for revision 1

[Bartosz Golaszewski]

2016-11-21 18:26 GMT+01:00 Jyri Sarha <jsarha@ti.com>:
> On 11/21/16 19:16, Bartosz Golaszewski wrote:
>> It has been determined that the highest resolution supported correctly
>> by LCDC rev1 is 800x600. Reduce the max_width value for rev1 to 800 in
>> crtc_max_width().
>>
>
> I don't think this is the right way to limit the supported video modes.
> There is technically there is no such limit, is there?
>
> If memory bandwidth is limiting the functionality of higher resolutions,
> you should use "max-bandwidth" tilcdc device-tree property [1].
>
> Cheers,
> Jyri
>

Will do, thanks.

Bartosz Golaszewski