On Wednesday 29 April 2015 08:44:09 Suravee Suthikulpanit wrote:
diff --git a/drivers/acpi/acpi_platform.c b/drivers/acpi/acpi_platform.c index 4bf7559..a4db208 100644 --- a/drivers/acpi/acpi_platform.c +++ b/drivers/acpi/acpi_platform.c @@ -108,9 +108,12 @@ struct platform_device *acpi_create_platform_device(struct acpi_device *adev) if (IS_ERR(pdev)) dev_err(&adev->dev, "platform device creation failed: %ld\n", PTR_ERR(pdev));
else
else {
arch_setup_dma_ops(&pdev->dev, 0, 0, NULL,
adev->flags.is_coherent); dev_dbg(&adev->dev, "created platform device %s\n", dev_name(&pdev->dev));
}
kfree(resources);
Looking at this code in more detail, it seems that it unconditionally sets pdevinfo.dma_mask = DMA_BIT_MASK(32), before calling arch_setup_dma_ops(). This assignment should really done inside of arch_setup_dma_ops() instead, which means we should implement that function on all architectures that support ACPI.
For the case where _CCA is missing (or coherency disabled, if you ask me), we would not call that function.
On a related note, I'm not sure how to handle different DMA masks here. arch_setup_dma_ops() gets passed a size (and offset) argument, which should match the DMA mask, but I don't know if there is a way to find out the size from ACPI. Should we assume it's always 64-bit DMA capable?
For legacy reasons, the default mask is probably best left at 32-bit, but drivers are expected to call dma_set_mask() if they can do 64-bit DMA, and that should fail based on the information provided by the platform if the bus is not capable of doing that.
Arnd