[PATCH] drm/etnaviv: init DMA ops for virtual master device

[Russell King - ARM Linux]

On Fri, Mar 09, 2018 at 11:12:37AM -0300, Fabio Estevam wrote:
> Hi Russell,
> 
> On Fri, Mar 9, 2018 at 8:34 AM, Russell King - ARM Linux
> <linux at armlinux.org.uk> wrote:
> > On Fri, Mar 09, 2018 at 12:20:59PM +0100, Lucas Stach wrote:
> >> All the DRM GEM dma-buf import/export operations are done through the
> >> virtual DRM master device. As this isn't instanciated from DT anymore
> >> we need to make sure the DMA ops are set up correctly.
> >>
> >> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> >> ---
> >>  drivers/gpu/drm/etnaviv/etnaviv_drv.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> >> index ab50090d066c..d7666aed943b 100644
> >> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> >> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> >> @@ -655,7 +655,8 @@ static int etnaviv_pdev_probe(struct platform_device *pdev)
> >>       struct device *dev = &pdev->dev;
> >>       struct component_match *match = NULL;
> >>
> >> -     dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32));
> >> +     arch_setup_dma_ops(dev, 0, 0x100000000, NULL, false);
> >> +     dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
> >
> > NAK.  dma_coerce_mask_and_coherent() exists for broken devices.  Please
> > instead ensure that the device is created with the proper default DMA
> > mask.
> 
> Should it be like this (like vc4_drv.c) ?
> 
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> @@ -578,6 +578,8 @@ static int etnaviv_bind(struct device *dev)
>         struct drm_device *drm;
>         int ret;
> 
> +       dev->coherent_dma_mask = DMA_BIT_MASK(32);
> +

No.  Drivers should be using dma_set_coherent_mask().

Whoever is creating this struct device has the responsibility to
initialise the DMA mask to something sensible.

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