[PATCH v5 6/7] mmc: zynq_sdhci: Wait till sd card detect state is stable

[Ashok Reddy Soma]

From: T Karthik Reddy <t.karthik.reddy at xilinx.com>

As per SD spec when SD host controller is reset, it takes 1000msec
to detect the card state. In case, if we enable the sd bus voltage &
card detect state is not stable, then host controller will disable
the sd bus voltage.

In case of warm/subsystem reboot, due to unstable card detect state
host controller is disabling the sd bus voltage to sd card causing
sd card timeout error. So we wait for a maximum of 1000msec to get
the card detect state stable before we enable the sd bus voltage.

This current fix is workaround for now, this needs to be analysed
further. Zynqmp platform should behave the same as Versal, but we
did not encounter this issue as of now. So we are fixing it for
Versal only.

Signed-off-by: T Karthik Reddy <t.karthik.reddy at xilinx.com>
Signed-off-by: Ashok Reddy Soma <ashok.reddy.soma at xilinx.com>
Reviewed-by: Jaehoon Chung <jh80.chung at samsung.com>
---

Changes in v5:
 - Added WORKAROUND in comment and elaborated the comment about issue.

Changes in v2:
 - Changed return error from -EIO to -ETIMEDOUT in arasan_sdhci_probe()
   in card detect state stable workaround

 drivers/mmc/zynq_sdhci.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/mmc/zynq_sdhci.c b/drivers/mmc/zynq_sdhci.c
index 9a1693940a..4a877b4ce8 100644
--- a/drivers/mmc/zynq_sdhci.c
+++ b/drivers/mmc/zynq_sdhci.c
@@ -776,6 +776,25 @@ static int arasan_sdhci_probe(struct udevice *dev)
 		return ret;
 	upriv->mmc = host->mmc;
 
+	/*
+	 * WORKAROUND: Versal platforms have an issue with card detect state.
+	 * Due to this, host controller is switching off voltage to sd card
+	 * causing sd card timeout error. Workaround this by adding a wait for
+	 * 1000msec till the card detect state gets stable.
+	 */
+	if (IS_ENABLED(CONFIG_ARCH_VERSAL)) {
+		u32 timeout = 1000;
+
+		while (((sdhci_readl(host, SDHCI_PRESENT_STATE) &
+			 SDHCI_CARD_STATE_STABLE) == 0) && timeout--) {
+			mdelay(1);
+		}
+		if (!timeout) {
+			dev_err(dev, "Sdhci card detect state not stable\n");
+			return -ETIMEDOUT;
+		}
+	}
+
 	return sdhci_probe(dev);
 }
 
-- 
2.17.1