Hi Vinod,
On 03/01/2019 12:45, Vinod Koul wrote:
> Hi Gustavo,
>
> On 03-01-19, 09:53, Gustavo Pimentel wrote:
>> Hi Vinod,
>>
>> (snipped)
>>
>>>>> +{
>>>>> + struct dw_edma_chan *chan = dchan2dw_edma_chan(dchan);
>>>>> + const struct dw_edma_core_ops *ops = chan2ops(chan);
>>>>> + enum dma_transfer_direction dir;
>>>>> + unsigned long flags;
>>>>> + int err = 0;
>>>>> +
>>>>> + spin_lock_irqsave(&chan->vc.lock, flags);
>>>>> +
>>>>> + if (!config) {
>>>>> + err = -EINVAL;
>>>>> + goto err_config;
>>>>> + }
>>>>> +
>>>>> + if (chan->configured) {
>>>>> + dev_err(chan2dev(chan), ": channel already configured\n");
>>>>> + err = -EPERM;
>>>>> + goto err_config;
>>>>> + }
>>>>> +
>>>>> + dir = config->direction;
>>>>
>>>> Direction is depreciated, I have already removed the usages, so please
>>>> do not add new ones.
>>>>
>>>> You need to take direction for respective prep_ calls
>>>
>>> Ok, I already do that. IMHO I found it strange to have the same information
>>> repeated on two places. But now that you say that this is deprecated, it makes
>>> sense now.
>>>
>>>>
>>>>> + if (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_WRITE) {
>>>>> + dev_info(chan2dev(chan),
>>>>> + ": direction DMA_DEV_TO_MEM (EDMA_DIR_WRITE)\n");
>>>>> + chan->p_addr = config->src_addr;
>>>>> + } else if (dir == DMA_MEM_TO_DEV && chan->dir == EDMA_DIR_READ) {
>>>>> + dev_info(chan2dev(chan),
>>>>> + ": direction DMA_MEM_TO_DEV (EDMA_DIR_READ)\n");
>>>>> + chan->p_addr = config->dst_addr;
>>>>> + } else {
>>>>> + dev_err(chan2dev(chan), ": invalid direction\n");
>>>>> + err = -EINVAL;
>>>>> + goto err_config;
>>>>> + }
>>>>
>>>> This should be removed
>>>
>>> Yeah, it was just for validation purposes. Now that direction is deprecated on
>>> the API, makes no sense to validate it.
>>>
>>>>
>>>>> +
>>>>> + dev_info(chan2dev(chan),
>>>>> + ": src_addr(physical) = 0x%.16x\n", config->src_addr);
>>>>> + dev_info(chan2dev(chan),
>>>>> + ": dst_addr(physical) = 0x%.16x\n", config->dst_addr);
>>>>
>>
>> I've a doubt now. As you know, for a DMA transfer you need the source and
>> destination addresses, which in the limited can be swapped according to the
>> direction MEM_TO_DEV/DEV_TO_MEM case.
>>
>> For the sake of simplicity, I'll just consider now the MEM_TO_DEV case, since
>> the other case is similar but the source and destination address are swapped.
>>
>> In my code I can get some of the information that I need by using the
>> sg_dma_address() in the scatter-gather list (which gives me the source address).
>>
>> The remaining information I got from here, using the direction to help me to
>> select which address I'll use later on the DMA transfer, in this case the
>> destination address.
>>
>> Since this is deprecated how should I proceed? How can I get that information?
>> There is some similar function to sg_dma_address() that could give me the
>> destination address?
>
> So the direction field is deprecated but rest of the configuration comes
> from from dma_slave_config. The user should set src_addr, dst_addr and
> then based on direction passed in the .device_prep_dma_* call arguments
> one can use one of these as peripheral address.
Ok, and the address given by sg_dma_address()? Is redundant or not applicable
for this case?
>
> Also, please keep in mind that for memory to memory transfers you should
> not expect the dma_slave_config to be used
My DMA implementation is only MEM_TO_DEV and DEV_TO_MEM.
>
> Thanks
>
Thanks.
