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    Subject[PATCH v1 11/11] mmc: mmci: Add Qcom specific pio_read function.
    Date
    From: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>

    MCIFIFOCNT register behaviour on Qcom chips is very different than the other
    pl180 integrations. MCIFIFOCNT register contains the number of
    words that are still waiting to be transferred through the FIFO. It keeps
    decrementing once the host CPU reads the MCIFIFO. With the existing logic and
    the MCIFIFOCNT behaviour, mmci_pio_read will loop forever, as the FIFOCNT
    register will always return transfer size before reading the FIFO.

    Also the data sheet states that "This register is only useful for debug
    purposes and should not be used for normal operation since it does not reflect
    data which may or may not be in the pipeline".

    This patch implements qcom_pio_read function so as existing mmci_pio_read is
    not suitable for Qcom SOCs.

    Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
    ---
    drivers/mmc/host/mmci.c | 31 +++++++++++++++++++++++++++++--
    1 file changed, 29 insertions(+), 2 deletions(-)

    diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
    index def1b19..45198b6 100644
    --- a/drivers/mmc/host/mmci.c
    +++ b/drivers/mmc/host/mmci.c
    @@ -1038,6 +1038,29 @@ 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)
    +{
    + uint32_t *ptr = (uint32_t *) buffer;
    + int count = 0;
    + struct variant_data *variant = host->variant;
    + int fifo_size = variant->fifosize;
    +
    + if (remain % 4)
    + remain = ((remain >> 2) + 1) << 2;
    +
    + while (readl(host->base + MMCISTATUS) & MCI_RXDATAAVLBL) {
    + *ptr = readl(host->base + MMCIFIFO + (count % fifo_size));
    + ptr++;
    + count += sizeof(uint32_t);
    +
    + remain -= sizeof(uint32_t);
    + if (remain == 0)
    + break;
    + }
    + return count;
    +}
    +
    static int mmci_pio_read(struct mmci_host *host, char *buffer, unsigned int remain)
    {
    void __iomem *base = host->base;
    @@ -1159,8 +1182,12 @@ static irqreturn_t mmci_pio_irq(int irq, void *dev_id)
    remain = sg_miter->length;

    len = 0;
    - if (status & MCI_RXACTIVE)
    - len = mmci_pio_read(host, buffer, remain);
    + if (status & MCI_RXACTIVE) {
    + if (host->hw_designer == AMBA_VENDOR_QCOM)
    + len = mmci_qcom_pio_read(host, buffer, remain);
    + else
    + len = mmci_pio_read(host, buffer, remain);
    + }
    if (status & MCI_TXACTIVE)
    len = mmci_pio_write(host, buffer, remain, status);

    --
    1.7.9.5


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