Re: [PATCH v4 13/13] mmc: mmci: Add Qcom specific pio_read function.

Srinivas Kandagatla
2014-05-30T11:44:43Z

Hi Ulf,

On 30/05/14 12:27, Ulf Hansson wrote:
> On 28 May 2014 15:48, <srinivas.kandagatla@linaro.org> wrote:
...

>> .f_max = 208000000,
>> .explicit_mclk_control = true,
>> + .qcom_fifo = true,
>> };
>>
>> static int mmci_card_busy(struct mmc_host *mmc)
>> @@ -1006,6 +1009,40 @@ mmci_cmd_irq(struct mmci_host *host, struct mmc_command *cmd,
>> }
>> }
>>
>> +static int mmci_qcom_pio_read(struct mmci_host *host, char *buffer,
>> + unsigned int remain)
>> +{
>> + u32 *ptr = (u32 *) buffer;
>
> Instead of u32 ptr above, I suggest to use a char *ptr. You need it
> anyway further down below where you move in step of bytes instead of
> words.
>
>> + unsigned int count = 0;
>> + unsigned int words, bytes;
>> + unsigned int fsize = host->variant->fifosize;
>> +
>> + words = remain >> 2;
>> + bytes = remain % 4;
>> + /* read full words followed by leftover bytes */
>> + if (words) {
>> + while (readl(host->base + MMCISTATUS) & MCI_RXDATAAVLBL) {
>
> How about while (words && (readl(host->base + MMCISTATUS) & MCI_RXDATAAVLBL)
>
> That would make it possible the remove the "if", both above and below.

That sounds sensible.. I will try it.
>
>> + *ptr = readl(host->base + MMCIFIFO + (count % fsize));
>
> This looks strange. :-) Depending on the count you will read an offset
> into the FIFO? Seems like a very awkward implementation of a FIFO in
> the HW. :-)
>
I got into weird issues when I tried using the mmci_pio_read, the fifo
implementation seems to be different. I dont have full details on the
fifo behaviour.

Most of this logic is inherited from 3.4 qcom andriod kernel.

> BTW, what does "MCI_RXDATAAVLBL" actually mean for the Qcom variant?

It means, At least 1 word in the RX FIFO. SW can read 1 word only from
the FIFO.

> How much data could you expect in the FIFO when this status is
> triggered?

> Are there no option of reading a number of words, depending on what
> type FIFO IRQ that was raised?
There are RXFIFO_HALF_FULL and RXFIFO_FULL bits in status register, but
I never tried to use them. Might be worth a try before I send next
version patches.

I will give a try and keep you posted.
Thanks,
srini
>
>> + ptr++;
>> + count += 4;
>> + words--;
>> + if (!words)
>> + break;
>> + }
>> + }
>> +
>> + if (bytes) {
>> + unsigned char buf[4];
>> + if (readl(host->base + MMCISTATUS) & MCI_RXDATAAVLBL) {
>> + *buf = readl(host->base + MMCIFIFO + (count % fsize));
>> + memcpy(ptr, buf, bytes);
>> + count += bytes;
>> + }
>> + }
>> +
>> + return count;
>> +}
>> +

>>
>
> Kind regards
> Ulf Hansson
>