linux-kernel - [PATCH AUTOSEL 3.18 15/41] mmc: omap: fix the maximum timeout setting

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Message-Id: <20190327182518.19394-15-sashal@kernel.org>
Date:   Wed, 27 Mar 2019 14:24:52 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Aaro Koskinen <aaro.koskinen@....fi>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Sasha Levin <sashal@...nel.org>, linux-omap@...r.kernel.org,
        linux-mmc@...r.kernel.org
Subject: [PATCH AUTOSEL 3.18 15/41] mmc: omap: fix the maximum timeout setting

From: Aaro Koskinen <aaro.koskinen@....fi>

[ Upstream commit a6327b5e57fdc679c842588c3be046c0b39cc127 ]

When running OMAP1 kernel on QEMU, MMC access is annoyingly noisy:

	MMC: CTO of 0xff and 0xfe cannot be used!
	MMC: CTO of 0xff and 0xfe cannot be used!
	MMC: CTO of 0xff and 0xfe cannot be used!
	[ad inf.]

Emulator warnings appear to be valid. The TI document SPRU680 [1]
("OMAP5910 Dual-Core Processor MultiMedia Card/Secure Data Memory Card
(MMC/SD) Reference Guide") page 36 states that the maximum timeout is 253
cycles and "0xff and 0xfe cannot be used".

Fix by using 0xfd as the maximum timeout.

Tested using QEMU 2.5 (Siemens SX1 machine, OMAP310), and also checked on
real hardware using Palm TE (OMAP310), Nokia 770 (OMAP1710) and Nokia N810
(OMAP2420) that MMC works as before.

[1] http://www.ti.com/lit/ug/spru680/spru680.pdf

Fixes: 730c9b7e6630f ("[MMC] Add OMAP MMC host driver")
Signed-off-by: Aaro Koskinen <aaro.koskinen@....fi>
Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/mmc/host/omap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index 11e5bfedab70..b9f4f39f9359 100644
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -921,7 +921,7 @@ static inline void set_cmd_timeout(struct mmc_omap_host *host, struct mmc_reques
 	reg &= ~(1 << 5);
 	OMAP_MMC_WRITE(host, SDIO, reg);
 	/* Set maximum timeout */
-	OMAP_MMC_WRITE(host, CTO, 0xff);
+	OMAP_MMC_WRITE(host, CTO, 0xfd);
 }
 
 static inline void set_data_timeout(struct mmc_omap_host *host, struct mmc_request *req)
-- 
2.19.1