linux-kernel - [PATCH] mmc: Fix read-only detection with JMicron 388 chip

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Date:	Thu, 21 Apr 2011 18:00:17 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Chris Ball <cjb@...top.org>
Cc:	Aries Lee <arieslee@...cron.com>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] mmc: 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 the own get_ro op
for checking the register more intensively with a relatively long
delay.

The patch is tested with 2.6.39-rc4 kernel.

Cc: Aries Lee <arieslee@...cron.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---
 drivers/mmc/host/sdhci-pci.c |   34 ++++++++++++++++++++++++++++++++++
 1 files changed, 34 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/host/sdhci-pci.c b/drivers/mmc/host/sdhci-pci.c
index a136be7..9037b2a 100644
--- a/drivers/mmc/host/sdhci-pci.c
+++ b/drivers/mmc/host/sdhci-pci.c
@@ -346,6 +346,35 @@ static void jmicron_enable_mmc(struct sdhci_host *host, int on)
 	writeb(scratch, host->ioaddr + 0xC0);
 }
 
+/* As PRESENT_STATE register becomes unstable just after plugging,
+ * need to check the RO-cap multiple times with a relatively long delay.
+ */
+
+#define SAMPLE_COUNT	5
+
+static unsigned int jmicron_get_ro(struct sdhci_host *host)
+{
+	int i, ro_count;
+
+	ro_count = 0;
+	for (i = 0; i < SAMPLE_COUNT; i++) {
+		int present = sdhci_readl(host, SDHCI_PRESENT_STATE);
+		if (!(present & SDHCI_WRITE_PROTECT)) {
+			if (++ro_count > SAMPLE_COUNT / 2)
+				return 1;
+		}
+		msleep(30);
+	}
+	return 0;
+}
+
+static int sdhci_pci_enable_dma(struct sdhci_host *host);
+
+static struct sdhci_ops jmicron_pci_ops = {
+	.enable_dma	= sdhci_pci_enable_dma,
+	.get_ro		= jmicron_get_ro,
+};
+
 static int jmicron_probe_slot(struct sdhci_pci_slot *slot)
 {
 	if (slot->chip->pdev->revision == 0) {
@@ -383,6 +412,11 @@ static int jmicron_probe_slot(struct sdhci_pci_slot *slot)
 
 	slot->host->mmc->caps |= MMC_CAP_BUS_WIDTH_TEST;
 
+	/* Replace the ops for unstable get_ro detection */
+	if (slot->chip->pdev->device == PCI_DEVICE_ID_JMICRON_JMB388_SD ||
+	    slot->chip->pdev->device == PCI_DEVICE_ID_JMICRON_JMB388_ESD)
+		slot->host->ops = &jmicron_pci_ops;
+
 	return 0;
 }
 
-- 
1.7.4.2

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