[PATCH] MMC: OMAP: fix the maximum timeout setting

From: Aaro Koskinen <aaro.koskinen@iki.fi>
To: Ulf Hansson <ulf.hansson@linaro.org>, linux-mmc@vger.kernel.org
Cc: linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org,
	Tony Lindgren <tony@atomide.com>,
	Aaro Koskinen <aaro.koskinen@iki.fi>
Subject: [PATCH] MMC: OMAP: fix the maximum timeout setting
Date: Sun,  3 Feb 2019 00:14:33 +0200	[thread overview]
Message-ID: <20190202221433.24717-1-aaro.koskinen@iki.fi> (raw)

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@iki.fi>
---
 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 c60a7625b1fa..b2873a2432b6 100644
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -920,7 +920,7 @@ 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)
-- 
2.17.0

