linux-kernel - Re: [PATCH v2 1/5] drm/rockchip: vop: optimize virtual stride calculate

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Message-ID: <5594D677.20202@rock-chips.com>
Date:	Thu, 02 Jul 2015 14:13:11 +0800
From:	Mark yao <mark.yao@...k-chips.com>
To:	Tomasz Figa <tfiga@...omium.org>
CC:	dri-devel <dri-devel@...ts.freedesktop.org>,
	David Airlie <airlied@...ux.ie>,
	Heiko Stuebner <heiko@...ech.de>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Daniel Vetter <daniel@...ll.ch>,
	Rob Clark <robdclark@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	sandy.huang@...k-chips.com, dkm@...k-chips.com, zwl@...k-chips.com,
	xw@...k-chips.com
Subject: Re: [PATCH v2 1/5] drm/rockchip: vop: optimize virtual stride calculate

On 2015年07月02日 12:59, Tomasz Figa wrote:
> On Fri, Jun 26, 2015 at 7:07 PM, Mark Yao <mark.yao@...k-chips.com> wrote:
>> vir_stride need number words of the virtual width, and fb->pitches
>> save bytes_per_pixel, so just div 4 switch to stride.
>>
>> Signed-off-by: Mark Yao <mark.yao@...k-chips.com>
>> ---
>> Changes in v2: None
>>
>>   drivers/gpu/drm/rockchip/rockchip_drm_vop.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> index 6188221..3c9f4f3 100644
>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
>> @@ -644,7 +644,7 @@ static int vop_update_plane_event(struct drm_plane *plane,
>>          offset += (src.y1 >> 16) * fb->pitches[0];
>>          yrgb_mst = rk_obj->dma_addr + offset;
>>
>> -       y_vir_stride = fb->pitches[0] / (fb->bits_per_pixel >> 3);
>> +       y_vir_stride = fb->pitches[0] >> 2;
> If the unit of y_vir_stride is words then doesn't it mean that the
> calculation before this patch was just invalid? If yes, shouldn't the
> subject actually say "Fix virtual stride calculation"?
>
> Best regards,
> Tomasz
>
>
>
Hi Tomasz
     the calculation thinking before is that:
        fb->pitches[0] = surface_width * bytes_per_pixel
        surface_width = fb->pitches[0] / bytes_per_pixel
                               = fb->pitches[0] / (fb->bits_per_pixel >> 3)

    means that "y_vir_stride = surface_width",

ARGB888 one pixel is word size, So that is right for ARGB888, but wrong for other formats.

You are right, subject say "Fix virtual stride calculation" is suitable.

Best regards,
-- 
Ｍark Yao


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