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@xxxxxxxxxxxxxx>
Signed-off-by: Michael Walle <michael@xxxxxxxx>
---
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) {
