linux-kernel - [PATCH v2 08/11] mmc: host: omap_hsmmc: Workaround for errata id i802

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Message-ID: <1440493542-26150-9-git-send-email-kishon@ti.com>
Date:	Tue, 25 Aug 2015 14:35:39 +0530
From:	Kishon Vijay Abraham I <kishon@...com>
To:	<ulf.hansson@...aro.org>, <afenkart@...il.com>, <tony@...mide.com>,
	<linux-mmc@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <nsekhar@...com>
CC:	<neilb@...e.de>, <kishon@...com>
Subject: [PATCH v2 08/11] mmc: host: omap_hsmmc: Workaround for errata id i802

According to errata i802, DCRC error interrupts
(MMCHS_STAT[21] DCRC=0x1) can occur during the tuning procedure.

The DCRC interrupt, occurs when the last tuning block fails
(the last ratio tested). The delay from CRC check until the
interrupt is asserted is bigger than the delay until assertion
of the tuning end flag. Assertion of tuning end flag is what
masks the interrupts. Because of this race, an erroneous DCRC
interrupt occurs.

The suggested  workaround is to disable DCRC interrupts during
the tuning procedure which is implemented here.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
Signed-off-by: Sekhar Nori <nsekhar@...com>
---
 drivers/mmc/host/omap_hsmmc.c |   11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
index 43485c3..9ab0f6e 100644
--- a/drivers/mmc/host/omap_hsmmc.c
+++ b/drivers/mmc/host/omap_hsmmc.c
@@ -665,8 +665,17 @@ static void omap_hsmmc_enable_irq(struct omap_hsmmc_host *host,
 	is_tuning = (cmd->opcode == MMC_SEND_TUNING_BLOCK) ||
 		    (cmd->opcode == MMC_SEND_TUNING_BLOCK_HS200);
 
-	if (!is_tuning && host->use_dma)
+	if (is_tuning) {
+		/*
+		 * OMAP5/DRA74X/DRA72x Errata i802:
+		 * DCRC error interrupts (MMCHS_STAT[21] DCRC=0x1) can occur
+		 * during the tuning procedure. So disable it during the
+		 * tuning procedure.
+		 */
+		irq_mask &= ~DCRC_EN;
+	} else if (host->use_dma) {
 		irq_mask &= ~(BRR_EN | BWR_EN);
+	}
 
 	/* Disable timeout for erases */
 	if (cmd->opcode == MMC_ERASE)
-- 
1.7.9.5

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