# Re: \[PATCH\] video: mxsfb: Fix framebuffer corruption on mx6sx

- From: Marek Vasut \<marex@denx.de\>
- Date: 2016-08-26 15:28:54 
- List: linux-fbdev
- Page: https://ratatoskr.run/linux-fbdev/2016/08/13466589
- Thread: https://ratatoskr.run/linux-fbdev/2016/08/13466587/t.md

```text
On 08/26/2016 04:38 PM, Lucas Stach wrote:
> Am Freitag, den 26.08.2016, 16:30 +0200 schrieb Marek Vasut:
>> Allocate the framebuffer memory as coherent, otherwise the framebuffer
>> will suffer from artifacts when displaying scrolling text or video.
>> This can be replicated on i.MX6SX (armv7), which has more complex memory
>> architecture compared to the i.MX23/28 (armv5).
>>
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> Cc: Tomi Valkeinen <redacted>
>> Cc: Fabio Estevam <redacted>
>> Cc: Lucas Stach <l.stach@pengutronix.de>
>> Cc: Shawn Guo <shawnguo@kernel.org>
>> ---
>>  drivers/video/fbdev/mxsfb.c | 10 ++++++----
>>  1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/video/fbdev/mxsfb.c b/drivers/video/fbdev/mxsfb.c
>> index 4e6608c..bd1a310 100644
>> --- a/drivers/video/fbdev/mxsfb.c
>> +++ b/drivers/video/fbdev/mxsfb.c
>> @@ -800,6 +800,7 @@ static int mxsfb_init_fbinfo(struct mxsfb_info *host,
>>  			struct fb_videomode *vmode)
>>  {
>>  	int ret;
>> +	struct device *dev = &host->pdev->dev;
>>  	struct fb_info *fb_info = &host->fb_info;
>>  	struct fb_var_screeninfo *var = &fb_info->var;
>>  	dma_addr_t fb_phys;
>> @@ -825,12 +826,11 @@ static int mxsfb_init_fbinfo(struct mxsfb_info *host,
>>  
>>  	/* Memory allocation for framebuffer */
>>  	fb_size = SZ_2M;
>> -	fb_virt = alloc_pages_exact(fb_size, GFP_DMA);
>> +	fb_virt = dma_alloc_coherent(dev, PAGE_ALIGN(fb_size), &fb_phys,
>> +				     GFP_KERNEL);
> 
> You probably want writecombined memory here instead of coherent. Using
> coherent memory for framebuffers sucks performance wise.

Ah, true. That'd be dma_{alloc,free}_wc() , right ?

-- 
Best regards,
Marek Vasut
```