On 2021-12-01 13:41, Lucas Stach wrote:
Hi Robin,
Am Mittwoch, dem 01.12.2021 um 12:50 +0000 schrieb Robin Murphy:
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.
From what I can see the dma_mask has allocated storage in the platform
device and does not point to the coherent dma mask, see
setup_pdev_dma_masks().
Urgh, apologies for the confusion - seems I had one of those mental
short-circuits and was utterly convinced that that's what the platform
device setup did, but of course it's only the fallback case in
of_dma_configure(). Sorry for the noise!
Cheers,
Robin.
