Messages in this thread | | | Date | Wed, 1 Dec 2021 12:50:15 +0000 | Subject | Re: [PATCH v2 3/3] drm/etnaviv: use a 32 bit mask as coherent DMA mask | From | Robin Murphy <> |
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Sorry I missed this earlier...
On 2021-09-07 17:49, Michael Walle wrote: > The STLB and the first command buffer (which is used to set up the TLBs) > has a 32 bit size restriction in hardware. There seems to be no way to > specify addresses larger than 32 bit. Keep it simple and restict the > addresses to the lower 4 GiB range for all coherent DMA memory > allocations. > > Please note, that platform_device_alloc() will initialize dev->dma_mask > to point to pdev->platform_dma_mask, thus dma_set_mask() will work as > expected. > > While at it, move the dma_mask setup code to the of_dma_configure() to > keep all the DMA setup code next to each other. > > Suggested-by: Lucas Stach <l.stach@pengutronix.de> > Signed-off-by: Michael Walle <michael@walle.cc> > --- > drivers/gpu/drm/etnaviv/etnaviv_drv.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c > index 54eb653ca295..0b756ecb1bc2 100644 > --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c > +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c > @@ -613,6 +613,24 @@ static int etnaviv_pdev_probe(struct platform_device *pdev) > component_match_add(dev, &match, compare_str, names[i]); > } > > + /* > + * PTA and MTLB can have 40 bit base addresses, but > + * unfortunately, an entry in the MTLB can only point to a > + * 32 bit base address of a STLB. Moreover, to initialize the > + * MMU we need a command buffer with a 32 bit address because > + * without an MMU there is only an indentity mapping between > + * the internal 32 bit addresses and the bus addresses. > + * > + * To make things easy, we set the dma_coherent_mask to 32 > + * bit to make sure we are allocating the command buffers and > + * TLBs in the lower 4 GiB address space. > + */ > + if (dma_set_mask(&pdev->dev, DMA_BIT_MASK(40)) || > + dma_set_coherent_mask(&pdev->dev, DMA_BIT_MASK(32))) {
Since AFAICS you're not changing the default dma_mask pointer to point to some storage other than the coherent mask, the dma_set_mask() call effectively does nothing and both masks will end up reading back as 32 bits.
Robin.
> + dev_dbg(&pdev->dev, "No suitable DMA available\n"); > + return -ENODEV; > + } > + > /* > * Apply the same DMA configuration to the virtual etnaviv > * device as the GPU we found. This assumes that all Vivante > @@ -671,8 +689,6 @@ static int __init etnaviv_init(void) > of_node_put(np); > goto unregister_platform_driver; > } > - pdev->dev.coherent_dma_mask = DMA_BIT_MASK(40); > - pdev->dev.dma_mask = &pdev->dev.coherent_dma_mask; > > ret = platform_device_add(pdev); > if (ret) { >
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