linux-kernel - Re: [PATCH 2/4] drm/exynos/mixer: use MXR_GRP_SXY

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Message-id: <536B0900.10204@samsung.com>
Date:	Thu, 08 May 2014 13:33:04 +0900
From:	Seung-Woo Kim <sw0312.kim@...sung.com>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	Inki Dae <inki.dae@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	David Airlie <airlied@...ux.ie>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sean Paul <seanpaul@...omium.org>,
	Stéphane Marchesin <marcheu@...omium.org>,
	Seung-Woo Kim <sw0312.kim@...sung.com>
Subject: Re: [PATCH 2/4] drm/exynos/mixer: use MXR_GRP_SXY_SY

Hello Daniel,

On 2014년 05월 07일 23:14, Daniel Kurtz wrote:
> On Wed, May 7, 2014 at 1:14 PM, Seung-Woo Kim <sw0312.kim@...sung.com> wrote:
>> Hi Daniel,
>>
>> On 2014년 05월 05일 00:26, Daniel Kurtz wrote:
>>> Mixer hardware supports offsetting dma from start of source buffer using
>>> the MXR_GRP_SXY register.
>>>
>>> Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
>>> ---
>>>  drivers/gpu/drm/exynos/exynos_mixer.c | 8 +++-----
>>>  1 file changed, 3 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
>>> index 475eb49..40cf39b 100644
>>> --- a/drivers/gpu/drm/exynos/exynos_mixer.c
>>> +++ b/drivers/gpu/drm/exynos/exynos_mixer.c
>>> @@ -529,13 +529,11 @@ static void mixer_graph_buffer(struct mixer_context *ctx, int win)
>>>
>>>       dst_x_offset = win_data->crtc_x;
>>>       dst_y_offset = win_data->crtc_y;
>>> +     src_x_offset = win_data->fb_x;
>>> +     src_y_offset = win_data->fb_y;
>>>
>>>       /* converting dma address base and source offset */
>>> -     dma_addr = win_data->dma_addr
>>> -             + (win_data->fb_x * win_data->bpp >> 3)
>>> -             + (win_data->fb_y * win_data->fb_width * win_data->bpp >> 3);
>>> -     src_x_offset = 0;
>>> -     src_y_offset = 0;
>>> +     dma_addr = win_data->dma_addr;
>>
>> Basically, you are right and source offset register can be used. But
>> because of limitation of resolution for mixer up to 1920x1080, I
>> considered modified soruce dma address to set one frame buffer, which is
>> bigger than 1920x1080, on to both fimd and hdmi.
> 
> Hi Seung-Woo,
> 
> I do not see why the maximum MIXER resolution matters for choosing
> between offsetting BASE or using SXY.
> 
> Let's say you have one big 1920x1908 framebuffer, with a span of 1920,
> starting at dma_addr (there is no extra padding at the end of the
> line).
> Let's say you wanted the mixer to scan out 1920x1080 pixels starting
> from (0, 800) in the framebuffer, and start drawing them at (0,0) on
> the screen.
> 
> What we currently do is:
>   BASE = dma_addr + (800 * 1080 * 4)
>   SPAN = 1920
>   SXY = SX(0) | SY(0)
>   WH = W(1920) | H(1080)
>   DXY = DX(0) | DY(0)
> 
> I am proposing we do:
>   BASE = dma_addr
>   SPAN = 1920
>   SXY = SX(0) | SY(800)
>   WH = W(1920) | H(1080)
>   DXY = DX(0) | DY(0)
> 
> In both cases, the mixer resolution is 1920x1080.

In my test to show each half of big one framebuffer (3840 x 1080) to
FIMD from 0 to 1079 and MIXER from 1080 to 3839 with exynos4210 and
exynos4412, it was failed to show proper hdmi display. Also it is same
for framebuffer (1920 x 2160). AFAIK, it is mainly because mixer dma has
limitation of dma memory size.

In this case, I set register as like:
  BASE = dma_addr /* 3840 x 1080 x 4 */
  SPAN = 3840
  SXY = SX(1920) | SY(0)
  WH = W(1920) | H(1080)
  DXY = DX(0) | DY(0)
or:
  BASE = dma_addr /* 1920 x 2160 x 4 */
  SPAN = 1920
  SXY = SX(0) | SY(1080)
  WH = W(1920) | H(1080)
  DXY = DX(0) | DY(0)
but these two setting did not show hdmi display as I expected. So I used
modified dma address.

> 
> My motivation for wanting to program an un-modified dma_addr into BASE
> is so we can then just check BASE_S to determine from which buffer the
> mixer is actively being scanned out without worrying about the source
> offset, since the source offset can change for a given framebuffer
> (for example, when doing panning, or if an overlay is used for a HW
> cursor).

Actually, this patch is exactly same with my first implementation, so I
completely understand your motivation. Anyway, I was focus on extended
displays with one buffer, so I wrote modified dma base address.

Thanks and Regards,
- Seung-Woo Kim

> 
> Best Regards,
> -Daniel
> 
>>
>> Regards,
>> - Seung-Woo Kim
>>
>>>
>>>       if (win_data->scan_flags & DRM_MODE_FLAG_INTERLACE)
>>>               ctx->interlace = true;
>>>
>>
>> --
>> Seung-Woo Kim
>> Samsung Software R&D Center
>> --
>>
> 

-- 
Seung-Woo Kim
Samsung Software R&D Center
--

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