[PATCH v2 6/7] ACPI/IORT: Don't set default coherent DMA mask
From: Lorenzo Pieralisi <hidden>
Date: 2018-07-25 15:27:47
Also in:
linux-acpi, linux-iommu
On Mon, Jul 23, 2018 at 11:16:11PM +0100, Robin Murphy wrote:
Now that we can track upstream DMA constraints properly with bus_dma_mask instead of trying (and failing) to maintain it in coherent_dma_mask, it doesn't make much sense for the firmware code to be touching the latter at all. It's merely papering over bugs wherein a driver has failed to call dma_set_coherent_mask() *and* the bus code has not initialised any default value.
Nit: I do not think the driver had a chance to probe and therefore call dma_set_coherent_mask() before iort_dma_setup() is executed, right ? Anyway, the patch makes perfect sense: Acked-by: Lorenzo Pieralisi <redacted>
quoted hunk ↗ jump to hunk
We don't really want to encourage more drivers coercing dma_mask so we'll continue to fix that up if necessary, but add a warning to help flush out any such buggy bus code that remains. CC: Lorenzo Pieralisi <redacted> CC: Hanjun Guo <redacted> CC: Sudeep Holla <redacted> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- drivers/acpi/arm64/iort.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c index bc51cff5505e..08f26db2da7e 100644 --- a/drivers/acpi/arm64/iort.c +++ b/drivers/acpi/arm64/iort.c@@ -978,20 +978,20 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size) int ret, msb; /* - * Set default coherent_dma_mask to 32 bit. Drivers are expected to - * setup the correct supported mask. + * If @dev is expected to be DMA-capable then the bus code that created + * it should have initialised its dma_mask pointer by this point. For + * now, we'll continue the legacy behaviour of coercing it to the + * coherent mask if not, but we'll no longer do so quietly. */ - if (!dev->coherent_dma_mask) - dev->coherent_dma_mask = DMA_BIT_MASK(32); - - /* - * Set it to coherent_dma_mask by default if the architecture - * code has not set it. - */ - if (!dev->dma_mask) + if (!dev->dma_mask) { + dev_warn(dev, "DMA mask not set\n"); dev->dma_mask = &dev->coherent_dma_mask; + } - size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1); + if (dev->coherent_dma_mask) + size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1); + else + size = 1ULL << 32; if (dev_is_pci(dev)) { ret = acpi_dma_get_range(dev, &dmaaddr, &offset, &size);-- 2.17.1.dirty