linux-kernel - SDHCI - Add QUIRK2_BROKEN_WRITE_PROTEXT

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Date:	Fri, 16 Aug 2013 12:14:50 +0000
From:	James Walmsley <james@...lfat-fs.co.uk>
To:	"monstr@...str.eu" <monstr@...str.eu>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: SDHCI - Add QUIRK2_BROKEN_WRITE_PROTEXT - Support Xilinx Zynq
 (Linux 3.9.0)

Hi Michal,

I have built a Xilinx Zynq based design which doesn't use the SDHCI Write-protect line.
However, we use the MIO_0 pin for configuring a multiplexer and consequently the
SDHCI driver thinks that the card is read-only (RO).

In the patch below I have proposed a new quirk, similar to the QUIRK_BROKEN_CARD_DETECTION
flag, which causes the sdhci driver to assume a card with RW access.

This patch was made against the latest tree from Xilinx (github.com/Xilinx/linux-xlnx), Kernel 3.9.0
and I have attached it to the LKML to propose the additional quirk which may be useful on other platforms.

Kind regards,

James Walmsley

---
 drivers/mmc/host/sdhci-of-xilinxps.c | 4 ++++
 drivers/mmc/host/sdhci.c             | 4 ++++
 include/linux/mmc/sdhci.h            | 1 +
 3 files changed, 9 insertions(+)

diff --git a/drivers/mmc/host/sdhci-of-xilinxps.c b/drivers/mmc/host/sdhci-of-xilinxps.c
index f79e0db..5553bc0 100644
--- a/drivers/mmc/host/sdhci-of-xilinxps.c
+++ b/drivers/mmc/host/sdhci-of-xilinxps.c
@@ -211,6 +211,10 @@ static int sdhci_zynq_probe(struct platform_device *pdev)
 	if (prop == NULL || (!(u32) be32_to_cpup(prop)))
 		host->quirks |= SDHCI_QUIRK_BROKEN_CARD_DETECTION;
 
+	prop = of_get_property(np, "xlnx,has-wp", NULL);
+	if (prop == NULL || (!(u32) be32_to_cpup(prop)))
+		host->quirks2 |= SDHCI_QUIRK2_BROKEN_WRITE_PROTECT;
+
 	return 0;
 
 clk_notif_unreg:
diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 51bbba4..c40365f 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -1609,6 +1609,10 @@ static int sdhci_do_get_ro(struct sdhci_host *host)
 {
 	int i, ro_count;
 
+	if(host->quirks2 & SDHCI_QUIRK2_BROKEN_WRITE_PROTECT) {
+		return 0;	// Return zero to assume RW.
+	}
+
 	if (!(host->quirks & SDHCI_QUIRK_UNSTABLE_RO_DETECT))
 		return sdhci_check_ro(host);
 
diff --git a/include/linux/mmc/sdhci.h b/include/linux/mmc/sdhci.h
index b838ffc..3eccf12 100644
--- a/include/linux/mmc/sdhci.h
+++ b/include/linux/mmc/sdhci.h
@@ -95,6 +95,7 @@ struct sdhci_host {
 /* The system physically doesn't support 1.8v, even if the host does */
 #define SDHCI_QUIRK2_NO_1_8_V				(1<<2)
 #define SDHCI_QUIRK2_PRESET_VALUE_BROKEN		(1<<3)
+#define SDHCI_QUIRK2_BROKEN_WRITE_PROTECT		(1<<4)
 
 	int irq;		/* Device IRQ */
 	void __iomem *ioaddr;	/* Mapped address */
-- 
1.8.1.2

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