[PATCH for-5.3] drm/omap: ensure we have a valid dma_mask
Tomi Valkeinen
tomi.valkeinen at ti.com
Fri Aug 9 06:40:32 UTC 2019
Hi,
On 08/08/2019 13:10, Christoph Hellwig wrote:
> The omapfb platform devices does not have a DMA mask set. The
> traditional arm DMA code ignores, but the generic dma-direct/swiotlb
> has stricter checks and thus fails mappings without a DMA mask.
> As we use swiotlb for arm with LPAE now, omap needs to catch up
> and actually set a DMA mask.
>
> Fixes: ad3c7b18c5b3 ("arm: use swiotlb for bounce buffering on LPAE configs")
> Reported-by: "H. Nikolaus Schaller" <hns at goldelico.com>
> Tested-by: "H. Nikolaus Schaller" <hns at goldelico.com>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
> drivers/gpu/drm/omapdrm/omap_fbdev.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/omapdrm/omap_fbdev.c b/drivers/gpu/drm/omapdrm/omap_fbdev.c
> index 561c4812545b..2c8abf07e617 100644
> --- a/drivers/gpu/drm/omapdrm/omap_fbdev.c
> +++ b/drivers/gpu/drm/omapdrm/omap_fbdev.c
> @@ -232,6 +232,8 @@ void omap_fbdev_init(struct drm_device *dev)
> if (!priv->num_pipes)
> return;
>
> + dma_coerce_mask_and_coherent(dev->dev, DMA_BIT_MASK(32));
> +
> fbdev = kzalloc(sizeof(*fbdev), GFP_KERNEL);
> if (!fbdev)
> goto fail;
>
We do call dma_set_coherent_mask() in omapdrm's probe() (in omap_drv.c),
but apparently that's not enough anymore. Changing that call to
dma_coerce_mask_and_coherent() removes the WARN. I can create a patch
for that, or Christoph can respin this one.
I am not too familiar with the dma mask handling, so maybe someone can
educate:
dma_coerce_mask_and_coherent() overwrites dev->dma_mask. Isn't that a
bad thing? What if the platform has set dev->dma_mask, and the driver
overwrites it with its value? Or who is supposed to set dev->dma_mask?
Tomi
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