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

[Srinivas Kandagatla]

Hi Ulf,

Managed to reuse the existing mmci_pio_read function with some minor 
modifications, Issue was with reading full fifo sizes which was creating 
the issue.

On 30/05/14 12:44, Srinivas Kandagatla wrote:
> 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.
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -73,6 +73,7 @@ static unsigned int fmax = 515633;
  * @busy_detect: true if busy detection on dat0 is supported
  * @pwrreg_nopower: bits in MMCIPOWER don't controls ext. power supply
  * @explicit_mclk_control: enable explicit mclk control in driver.
+ * @qcom_fifo: enables qcom specific fifo pio read logic.
  */
 struct variant_data {
        unsigned int            clkreg;
@@ -95,6 +96,7 @@ struct variant_data {
        bool                    busy_detect;
        bool                    pwrreg_nopower;
        bool                    explicit_mclk_control;
+       bool                    qcom_fifo;
 };

 static struct variant_data variant_arm = {
@@ -990,15 +992,33 @@ mmci_cmd_irq(struct mmci_host *host, struct 
mmc_command *cmd,
        }
 }

+static int mmci_get_rx_fifocnt(struct mmci_host *host, u32 status, int 
remain)
+{
+       return remain - (readl(host->base + MMCIFIFOCNT) << 2);
+}
+
+static int mmci_qcom_get_rx_fifocnt(struct mmci_host *host, u32 status, 
int r)
+{
+       /*
+        * on qcom SDCC4 only 8 words are used in each burst so only 8 
addresses
+        * from the fifo range should be used
+        */
+       if (status & MCI_RXFIFOHALFFULL)
+               return host->variant->fifohalfsize;
+       else
+               return 4;
+}
+
 static int mmci_pio_read(struct mmci_host *host, char *buffer, 
unsigned int remain)
 {
        void __iomem *base = host->base;
        char *ptr = buffer;
-       u32 status;
+       int hf = host->variant->fifohalfsize;
        int host_remain = host->size;
+       u32 status = readl(host->base + MMCISTATUS);

        do {
-               int count = host_remain - (readl(base + MMCIFIFOCNT) << 2);
+               int count = host->get_rx_fifocnt(host, status, host_remain);

                if (count > remain)
                        count = remain;
@@ -1488,6 +1508,11 @@ static int mmci_probe(struct amba_device *dev,
        if (ret)
                goto host_free;

+       if (variant->qcom_fifo)
+               host->get_rx_fifocnt = mmci_qcom_get_rx_fifocnt;
+       else
+               host->get_rx_fifocnt = mmci_get_rx_fifocnt;
+
        host->plat = plat;
        host->variant = variant;
        host->mclk = clk_get_rate(host->clk);
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index b5f0810..5f76670 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -229,6 +229,7 @@ struct mmci_host {
        /* pio stuff */
        struct sg_mapping_iter  sg_miter;
        unsigned int            size;
+       int (*get_rx_fifocnt)(struct mmci_host *h, u32 status, int remain);

 #ifdef CONFIG_DMA_ENGINE
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