linux-kernel - Re: [PATCH] drm/sun4i: Add DMA mask and segment size

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Date:   Fri, 17 Jun 2022 06:13:06 +0200
From:   Jernej Škrabec <jernej.skrabec@...il.com>
To:     mripard@...nel.org, wens@...e.org,
        Samuel Holland <samuel@...lland.org>
Cc:     airlied@...ux.ie, daniel@...ll.ch, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/sun4i: Add DMA mask and segment size

Dne petek, 17. junij 2022 ob 05:03:11 CEST je Samuel Holland napisal(a):
> Hi Jernej,
> 
> On 6/16/22 4:32 PM, Jernej Skrabec wrote:
> > Kernel occasionally complains that there is mismatch in segment size
> > when trying to render HW decoded videos and rendering them directly with
> > sun4i DRM driver.
> > 
> > Fix that by setting DMA mask and segment size.
> > 
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@...il.com>
> > ---
> > 
> >  drivers/gpu/drm/sun4i/sun4i_drv.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/sun4i/sun4i_drv.c
> > b/drivers/gpu/drm/sun4i/sun4i_drv.c index 275f7e4a03ae..83f4e87f77f6
> > 100644
> > --- a/drivers/gpu/drm/sun4i/sun4i_drv.c
> > +++ b/drivers/gpu/drm/sun4i/sun4i_drv.c
> > @@ -7,6 +7,7 @@
> > 
> >   */
> >  
> >  #include <linux/component.h>
> > 
> > +#include <linux/dma-mapping.h>
> > 
> >  #include <linux/kfifo.h>
> >  #include <linux/module.h>
> >  #include <linux/of_graph.h>
> > 
> > @@ -367,6 +368,9 @@ static int sun4i_drv_probe(struct platform_device
> > *pdev)> 
> >  	INIT_KFIFO(list.fifo);
> > 
> > +	dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> 
> Isn't this already the default, from of_dma_configure_id or
> setup_pdev_dma_masks?

Not sure, I need to check.

> > +	dma_set_max_seg_size(&pdev->dev, DMA_BIT_MASK(32));
> 
> This looks like a good change. In fact, I think we need a similar change in
> some other drivers.

Should be DMA_BIT_MASK(25) as in your other patch?

Best regards,
Jernej

> 
> Regards,
> Samuel