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

Srinivas Kandagatla
2014-05-30T16:21:02Z

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