linux-kernel - [PATCH 18/18] MMC: OMAP: Do not busy wait for end of command for ever

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Date:	Wed, 26 Mar 2008 16:10:02 -0400
From:	Carlos Aguiar <carlos.aguiar@...t.org.br>
To:	ext Pierre Ossman <drzeus-list@...eus.cx>
CC:	Tony Lindgren <tony@...mide.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 18/18] MMC: OMAP: Do not busy wait for end of command for
 ever

From: Jarkko Lavinen <jarkko.lavinen@...ia.com>

The limit was a fixed 100k limit in the busy loop, which is not
accurate. It would better to have time limit for the worst case
which occurs when sending 80 cycles at 400 kHz and takes about
200 microseconds, so limit the max time spend in the busy loop
for some 250 microseconds.

Signed-off-by: Jarkko Lavinen <jarkko.lavinen@...ia.com>
---
 drivers/mmc/host/omap.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index b28ae3b..2468e2f 100644
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -1276,11 +1276,17 @@ static void mmc_omap_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 		OMAP_MMC_WRITE(host, CON, dsor);
 	slot->saved_con = dsor;
 	if (ios->power_mode == MMC_POWER_ON) {
+		/* worst case at 400kHz, 80 cycles makes 200 microsecs */
+		int usecs = 250;
+
 		/* Send clock cycles, poll completion */
 		OMAP_MMC_WRITE(host, IE, 0);
 		OMAP_MMC_WRITE(host, STAT, 0xffff);
 		OMAP_MMC_WRITE(host, CMD, 1 << 7);
-		while ((OMAP_MMC_READ(host, STAT) & 1) == 0);
+		while (usecs > 0 && (OMAP_MMC_READ(host, STAT) & 1) == 0) {
+			udelay(1);
+			usecs--;
+		}
 		OMAP_MMC_WRITE(host, STAT, 1);
 	}
 
-- 1.5.3.GIT

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