On 6/10/19 3:18 AM, Christoph Hellwig wrote:
> On Sat, Jun 08, 2019 at 04:52:24PM -0500, Larry Finger wrote:
>> On 6/7/19 12:29 PM, Christoph Hellwig wrote:
>>> I don't think we should work around this in the driver, we need to fix
>>> it in the core. I'm curious why my previous patch didn't work. Can
>>> you throw in a few printks what failed? I.e. did dma_direct_supported
>>> return false? Did the actual allocation fail?
>>
>> Routine dma_direct_supported() returns true.
>>
>> The failure is in routine dma_set_mask() in the following if test:
>>
>> if (!dev->dma_mask || !dma_supported(dev, mask))
>> return -EIO;
>>
>> For b43legacy, dev->dma_mask is 0xc265684800000000.
>> dma_supported(dev, mask) is 0xc08b000000000000, mask is 0x3fffffff, and
>> the routine returns -EIO.
>>
>> For b43, dev->dma_mask is 0xc265684800000001,
>> dma_supported(dev, mask) is 0xc08b000000000000, mask is 0x77777777, and
>> the routine returns 0.
>
> I don't fully understand what values the above map to. Can you send
> me your actual debugging patch as well?
I do not understand why the if statement returns true as neither of the values
is zero. After seeing the x86 output shown below, I also do not understand all
the trailing zeros.
My entire patch is attached. That output came from this section:
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index f7afdad..ba2489d 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -317,9 +317,12 @@ int dma_supported(struct device *dev, u64 mask)
int dma_set_mask(struct device *dev, u64 mask)
{
+ pr_info("mask 0x%llx, dma_mask 0x%llx, dma_supported 0x%llx\n", mask,
dev->dma_mask,
+ dma_supported(dev, mask));
if (!dev->dma_mask || !dma_supported(dev, mask))
return -EIO;
+ pr_info("Continuing in dma_set_mask()\n");
arch_dma_set_mask(dev, mask);
dma_check_mask(dev, mask);
*dev->dma_mask = mask;
On a 32-bit x86 computer with 1GB of RAM, that same output was
For b43legacy, dev->dma_mask is 0x01f4029044.
dma_supported(dev, mask) is 0x1ef37f7000, mask is 0x3fffffff, and
the routine returns 0. 30-bit DMA works.
For b43, dev->dma_mask is 0x01f4029044,
dma_supported(dev, mask) is 0x1ef37f7000, mask is 0xffffffff, and
the routine also returns 0. This card supports 32-bit DMA.
Larry