Hi Russell,
On 03/10/2015 01:05 PM, Russell King - ARM Linux wrote:
> On Fri, Mar 06, 2015 at 11:47:48PM +0200, Grygorii.Strashko@xxxxxxxxxx wrote:
>> On 03/05/2015 10:17 PM, Russell King - ARM Linux wrote:
>>> On Thu, Mar 05, 2015 at 08:55:07PM +0200, Grygorii.Strashko@xxxxxxxxxx wrote:
>>>> The dma_coerce_mask_and_coherent() will fail in case 'Example 3' and succeed in cases 1,2.
>>>> dma-mapping.c --> __dma_supported()
>>>> if (sizeof(mask) != sizeof(dma_addr_t) && <== true for all OMAP4+
>>>> mask > (dma_addr_t)~0 && <== true for DMA_BIT_MASK(64)
>>>> dma_to_pfn(dev, ~0) < max_pfn) { <== true only for Example 3
>>>
>>> Hmm, I think this may make more sense to be "< max_pfn - 1" here, as
>>> that would be better suited to our intention.
>>>
>>> The result of dma_to_pfn(dev, ~0) is the maximum PFN which we could
>>> address via DMA, but we're comparing it with the maximum PFN in the
>>> system plus 1 - so we need to subtract one from it.
>>
>> Ok. I'll try it.
>
> Any news on this - I think it is a real off-by-one bug which we should
> fix in any case.
Sorry for delay, there was a day-off on my side.
As per my test results - with above change
dma_coerce_mask_and_coherent(DMA_BIT_MASK(64)) and friends will succeed always.
=========== Test results:
==== Test case 1:
Input data:
- RAM: start = 0x80000000 size = 0x80000000
- CONFIG_ARM_LPAE=n and sizeof(phys_addr_t) = 4
a) NO changes:
memory registered within memblock as:
memory.cnt = 0x1
memory[0x0] [0x00000080000000-0x000000fffffffe], 0x7fffffff bytes flags: 0x0
max_pfn = 0xFFFFF
max_mapnr = 0x7FFFF
dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded
b) with change in __dma_supported():
if (sizeof(mask) != sizeof(dma_addr_t) &&
mask > (dma_addr_t)~0 &&
- dma_to_pfn(dev, ~0) < max_pfn) {
+ dma_to_pfn(dev, ~0) < (max_pfn - 1)) {
if (warn) {
memory registered within memblock as:
memory.cnt = 0x1
memory[0x0] [0x00000080000000-0x000000fffffffe], 0x7fffffff bytes flags: 0x0
max_pfn = 0xFFFFF
max_mapnr = 0x7FFFF
dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded
==== Test case 2:
Input data:
- RAM: start = 0x80000000 size = 0x80000000
- CONFIG_ARM_LPAE=y and sizeof(phys_addr_t) = 8
a) NO changes:
memory registered within memblock as:
memory.cnt = 0x1
memory[0x0] [0x00000080000000-0x000000ffffffff], 0x80000000 bytes flags: 0x0
max_pfn = 0x100000
max_mapnr = 0x80000
dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- failed
[ 5.468470] asoc-simple-card sound@0: Coherent DMA mask 0xffffffffffffffff is larger than dma_addr_t allows
[ 5.478706] asoc-simple-card sound@0: Driver did not use or check the return value from dma_set_coherent_mask()?
[ 5.496620] davinci-mcasp 48468000.mcasp: ASoC: pcm constructor failed: -5
[ 5.503844] asoc-simple-card sound@0: ASoC: can't create pcm davinci-mcasp.0-tlv320aic3x-hifi :-5
b) with change in __dma_supported():
if (sizeof(mask) != sizeof(dma_addr_t) &&
mask > (dma_addr_t)~0 &&
- dma_to_pfn(dev, ~0) < max_pfn) {
+ dma_to_pfn(dev, ~0) < (max_pfn - 1)) {
if (warn) {
memory registered within memblock as:
memory.cnt = 0x1
memory[0x0] [0x00000080000000-0x000000ffffffff], 0x80000000 bytes flags: 0x0
max_pfn = 0x100000
max_mapnr = 0x80000
dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64)); -- succeeded
regards,
-grygorii
--
regards,
-grygorii
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