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

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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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