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SubjectRe: [PATCH] of: calculate masks of the device based on dma-range size
On 02/09/2015 06:27 AM, Catalin Marinas wrote:
> On Fri, Feb 06, 2015 at 03:15:20PM -0500, Murali Karicheri wrote:
>> diff --git a/drivers/of/device.c b/drivers/of/device.c
>> index 314c8a9..44209fa 100644
>> --- a/drivers/of/device.c
>> +++ b/drivers/of/device.c
>> @@ -83,17 +83,18 @@ int of_device_add(struct platform_device *ofdev)
>> */
>> void of_dma_configure(struct device *dev, struct device_node *np)
>> {
>> - u64 dma_addr, paddr, size;
>> + u64 dma_addr = 0, paddr, size;
>> int ret;
>> bool coherent;
>> - unsigned long offset;
>> + unsigned long offset = 0;
>> struct iommu_ops *iommu;
>>
>> /*
>> * Set default dma-mask to 32 bit. Drivers are expected to setup
>> * the correct supported dma_mask.
>> */
>> - dev->coherent_dma_mask = DMA_BIT_MASK(32);
>> + if (!dev->coherent_dma_mask)
>> + dev->coherent_dma_mask = DMA_BIT_MASK(32);
>>
>> /*
>> * Set it to coherent_dma_mask by default if the architecture
>> @@ -102,11 +103,14 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>> if (!dev->dma_mask)
>> dev->dma_mask =&dev->coherent_dma_mask;
>>
>> + /*
>> + * Set default size to cover the 32-bit. Drivers are expected to setup
>> + * the correct size and dma_mask.
>> + */
>
> Nitpick: drivers don't set up the size, just the mask. We read the size
> from DT.

Not sure how this came, I will update this.
>
>> + size = 1ULL<< 32;
>> +
>> ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
>> - if (ret< 0) {
>> - dma_addr = offset = 0;
>> - size = dev->coherent_dma_mask + 1;
>
> Do you assume that, on error, of_dma_get_range() does not touch any of
> the dma_addr/paddr/size? It looks safer to me to leave it as the
> original.
I think dma_addr and paddr is both modified on error. So this change
can't be done. I will revert the logic back to original.
>
>> - } else {
>> + if (!ret) {
>> offset = PFN_DOWN(paddr - dma_addr);
>>
>> /*
>> @@ -128,6 +132,15 @@ void of_dma_configure(struct device *dev, struct device_node *np)
>>
>> dev->dma_pfn_offset = offset;
>>
>> + /*
>> + * Limit coherent and dma mask based on size and default mask
>> + * set by the driver.
>> + */
>> + dev->coherent_dma_mask = min(dev->coherent_dma_mask,
>> + DMA_BIT_MASK(ilog2(dma_addr + size)));
>
> Do we need to cover the case where size is incorrectly set to 0 in the
> DT? At least some warning and leaving the mask unchanged.

The previous series already warn and return if the size is incorrect
(Patch v6 3/7) and leave the dma mask unchanged. So we don't have to do
anything in this patch. I will fix the above and re-send.
>
>> + *dev->dma_mask = min((*dev->dma_mask),
>> + DMA_BIT_MASK(ilog2(dma_addr + size)));
>> +
>> coherent = of_dma_is_coherent(np);
>> dev_dbg(dev, "device is%sdma coherent\n",
>> coherent ? " " : " not ");
>


--
Murali Karicheri
Linux Kernel, Texas Instruments


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