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 <lorenzo.pieralisi@xxxxxxx>
> 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 <lorenzo.pieralisi@xxxxxxx>
> CC: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
> CC: Sudeep Holla <sudeep.holla@xxxxxxx>
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> ---
> 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
>
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