linux-kernel - [PATCHv2 4/5] mmc: shdci-bcm2835: add verify for 32-bit back-to-back workaround

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Date:	Wed, 29 Oct 2014 23:36:56 -0700
From:	Scott Branden <sbranden@...adcom.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>,
	Russell King <rmk+kernel@....linux.org.uk>,
	Peter Griffin <peter.griffin@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Chris Ball <chris@...ntf.net>,
	Piotr Krol <pietrushnic@...il.com>
CC:	<linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Joe Perches <joe@...ches.com>,
	<linux-rpi-kernel@...ts.infradead.org>,
	Ray Jui <rjui@...adcom.com>,
	<bcm-kernel-feedback-list@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>
Subject: [PATCHv2 4/5] mmc: shdci-bcm2835: add verify for 32-bit back-to-back workaround

Add a verify option to driver to print out an error message if a
potential back to back write could cause a clock domain issue.

Signed-off-by: Scott Branden <sbranden@...adcom.com>
---
 drivers/mmc/host/Kconfig         |    9 +++++++++
 drivers/mmc/host/sdhci-bcm2835.c |   17 +++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
index 1386065..020de98 100644
--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -292,6 +292,15 @@ config MMC_SDHCI_BCM2835
 
 	  If unsure, say N.
 
+config MMC_SDHCI_BCM2835_VERIFY_WORKAROUND
+	bool "Verify BCM2835 workaround does not do back to back writes"
+	depends on MMC_SDHCI_BCM2835
+	default y
+	help
+	  This enables code that verifies the bcm2835 workaround.
+	  The verification code checks that back to back writes to the same
+	  register do not occur.
+
 config MMC_MOXART
 	tristate "MOXART SD/MMC Host Controller support"
 	depends on ARCH_MOXART && MMC
diff --git a/drivers/mmc/host/sdhci-bcm2835.c b/drivers/mmc/host/sdhci-bcm2835.c
index f8c450a..11af27f 100644
--- a/drivers/mmc/host/sdhci-bcm2835.c
+++ b/drivers/mmc/host/sdhci-bcm2835.c
@@ -27,6 +27,9 @@
 struct bcm2835_sdhci_host {
 	u32 shadow_cmd;
 	u32 shadow_blk;
+#ifdef CONFIG_MMC_SDHCI_BCM2835_VERIFY_WORKAROUND
+	int previous_reg;
+#endif
 };
 
 #define REG_OFFSET_IN_BITS(reg) ((reg) << 3 & 0x18)
@@ -58,6 +61,20 @@ static u8 bcm2835_sdhci_readb(struct sdhci_host *host, int reg)
 static inline void bcm2835_sdhci_writel(struct sdhci_host *host,
 						u32 val, int reg)
 {
+#ifdef CONFIG_MMC_SDHCI_BCM2835_VERIFY_WORKAROUND
+	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
+	struct bcm2835_sdhci_host *bcm2835_host = pltfm_host->priv;
+
+	if (bcm2835_host->previous_reg == reg) {
+		if ((reg != SDHCI_HOST_CONTROL)
+			&& (reg != SDHCI_CLOCK_CONTROL)) {
+			dev_err(mmc_dev(host->mmc),
+			"back-to-back write to 0x%x\n", reg);
+		}
+	}
+	bcm2835_host->previous_reg = reg;
+#endif
+
 	writel(val, host->ioaddr + reg);
 }
 
-- 
1.7.9.5

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