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

[Srinivas Kandagatla]

Hi Ulf,

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