mmc: sdhci: Fix read-only detection with JMicron 388 chip

On HP laptops with JMicron 388 chip, the write-locked SD card isn't
detected correctly as read-only in many cases.  This is because the
PRESENT_STATE register becomes unsable just after plugging, and it
returns the WRITE_PROTECT bit wrongly at the first read.

This patch fixes the read-only detection by adding a new sdhci quirk
indicating to check the register more intensively with a relatively
long delay.

The patch is tested with 2.6.39-rc4 kernel.

Cc: Aries Lee <arieslee@jmicron.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 24 insertions, 4 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index a70a3d1ef35..e5cfe70dc23 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1256,14 +1256,11 @@ out:
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
-static int sdhci_get_ro(struct mmc_host *mmc)
+static int check_ro(struct sdhci_host *host)
 {
-	struct sdhci_host *host;
 	unsigned long flags;
 	int is_readonly;
 
-	host = mmc_priv(mmc);
-
 	spin_lock_irqsave(&host->lock, flags);
 
 	if (host->flags & SDHCI_DEVICE_DEAD)
@@ -1281,6 +1278,29 @@ static int sdhci_get_ro(struct mmc_host *mmc)
 		!is_readonly : is_readonly;
 }
 
+#define SAMPLE_COUNT	5
+
+static int sdhci_get_ro(struct mmc_host *mmc)
+{
+	struct sdhci_host *host;
+	int i, ro_count;
+
+	host = mmc_priv(mmc);
+
+	if (!(host->quirks & SDHCI_QUIRK_UNSTABLE_RO_DETECT))
+		return check_ro(host);
+
+	ro_count = 0;
+	for (i = 0; i < SAMPLE_COUNT; i++) {
+		if (check_ro(host)) {
+			if (++ro_count > SAMPLE_COUNT / 2)
+				return 1;
+		}
+		msleep(30);
+	}
+	return 0;
+}
+
 static void sdhci_enable_sdio_irq(struct mmc_host *mmc, int enable)
 {
 	struct sdhci_host *host;