mmc: sunxi: Add card busy detection

Some sdio wifi modules have not been working reliable with the sunxi-mmc
host code. This turns out to be caused by starting new io-rw commands while
the card signals that it is still busy processing a previous command.

This commit adds card-busy detection to the sunxi-mmc driver which together
with recent core changes to check card-busy before starting io-rw commands
fixes the wifi reliability issues on the Cubietruck and other sunxi boards
using sdio wifi.
Reported-by: Eugene K <sigintmailru@gmail.com>
Suggested-by: Eugene K <sigintmailru@gmail.com>
Cc: Eugene K <sigintmailru@gmail.com>
Cc: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sunxi-mmc.c

@@ -873,6 +873,13 @@ static void sunxi_mmc_request(struct mmc_host *mmc, struct mmc_request *mrq)
 	spin_unlock_irqrestore(&host->lock, iflags);
 }
 
+static int sunxi_mmc_card_busy(struct mmc_host *mmc)
+{
+	struct sunxi_mmc_host *host = mmc_priv(mmc);
+
+	return !!(mmc_readl(host, REG_STAS) & SDXC_CARD_DATA_BUSY);
+}
+
 static const struct of_device_id sunxi_mmc_of_match[] = {
 	{ .compatible = "allwinner,sun4i-a10-mmc", },
 	{ .compatible = "allwinner,sun5i-a13-mmc", },
@@ -888,6 +895,7 @@ static struct mmc_host_ops sunxi_mmc_ops = {
 	.get_cd		 = mmc_gpio_get_cd,
 	.enable_sdio_irq = sunxi_mmc_enable_sdio_irq,
 	.hw_reset	 = sunxi_mmc_hw_reset,
+	.card_busy	 = sunxi_mmc_card_busy,
 };
 
 static const struct sunxi_mmc_clk_delay sunxi_mmc_clk_delays[] = {