ARM: 7552/1: mmc: mmci: Switching off HWFC for SDIO depends on MCLK

For writes, HWFC shall be switched off when transfer size <= 8
bytes and when MCLK rate is above 50 MHz. For 50MHz and below
it shall be switched off when transfer size < 8 bytes.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Johan Rudholm <johan.rudholm@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 7 insertions, 5 deletions

diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
index 877079e778cd..cd0fbee0b1c0 100644
--- a/drivers/mmc/host/mmci.c
+++ b/drivers/mmc/host/mmci.c
@@ -664,12 +664,14 @@ static void mmci_start_data(struct mmci_host *host, struct mmc_data *data)
                         datactrl |= MCI_ST_DPSM_SDIOEN;
 
                         /*
-                         * The ST Micro variant for SDIO transfer sizes
-                         * less then 8 bytes should have clock H/W flow
-                         * control disabled.
+                         * The ST Micro variant for SDIO small write transfers
+                         * needs to have clock H/W flow control disabled,
+                         * otherwise the transfer will not start. The threshold
+                         * depends on the rate of MCLK.
                          */
-                        if ((host->size < 8) &&
-                            (data->flags & MMC_DATA_WRITE))
+                        if (data->flags & MMC_DATA_WRITE &&
+                            (host->size < 8 ||
+                             (host->size <= 8 && host->mclk > 50000000)))
                                 clk = host->clk_reg & ~variant->clkreg_enable;
                         else
                                 clk = host->clk_reg | variant->clkreg_enable;