Re: [PATCH v3 2/4] of: move of_dma_configure() to device,c to help re-use

Murali Karicheri
2015-01-08T19:26:36Z

On 01/08/2015 03:40 AM, Arnd Bergmann wrote:
> On Wednesday 07 January 2015 17:37:56 Rob Herring wrote:
>> On Wed, Jan 7, 2015 at 12:49 PM, Murali Karicheri<m-karicheri2@ti.com> wrote:
>>
>>> + ret = of_dma_get_range(np,&dma_addr,&paddr,&size);
>>> + if (ret< 0) {
>>> + dma_addr = offset = 0;
>>> + size = dev->coherent_dma_mask + 1;
>>
>> If coherent_dma_mask is DMA_BIT_MASK(64), then you will overflow and
>> have a size of 0. There may also be a problem when the mask is only
>> 32-bit type.
>
> The mask is always a 64-bit type, it's not optional. But you are right,
> the 64-bit mask case is broken, so I guess we have to fix it differently
> by always passing the smaller value into arch_setup_dma_ops and
> adapting that function instead.
Arnd,

What is the smaller value you are referring to in the below code?
between *dev->dma_mask and size from DT? But overflow can still happen
when size is to be calculated in arch_setup_dma_ops() for Non DT case or
when DT size is configured to be equivalent of DMA_BIT_MASK(64) + 1. Can
we discuss the code change you have in mind when you get a chance?

Murali
>
> Arnd

--
Murali Karicheri
Linux Kernel, Texas Instruments