linux-kernel - [ 27/42] mmc: atmel-mci: correct data timeout computation

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Message-Id: <20120411231312.018775228@linuxfoundation.org>
Date:	Wed, 11 Apr 2012 16:13:34 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Chris Ball <cjb@...top.org>
Subject: [ 27/42] mmc: atmel-mci: correct data timeout computation

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ludovic Desroches <ludovic.desroches@...el.com>

commit 66292ad92c6d3f2f1c137a1c826b331ca8595dfd upstream.

The HSMCI operates at a rate of up to Master Clock divided by two.
Moreover previous calculation can cause overflows and so wrong
timeouts.

Signed-off-by: Ludovic Desroches <ludovic.desroches@...el.com>
Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
Signed-off-by: Chris Ball <cjb@...top.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/mmc/host/atmel-mci.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/mmc/host/atmel-mci.c
+++ b/drivers/mmc/host/atmel-mci.c
@@ -468,7 +468,14 @@ err:
 static inline unsigned int ns_to_clocks(struct atmel_mci *host,
 					unsigned int ns)
 {
-	return (ns * (host->bus_hz / 1000000) + 999) / 1000;
+	/*
+	 * It is easier here to use us instead of ns for the timeout,
+	 * it prevents from overflows during calculation.
+	 */
+	unsigned int us = DIV_ROUND_UP(ns, 1000);
+
+	/* Maximum clock frequency is host->bus_hz/2 */
+	return us * (DIV_ROUND_UP(host->bus_hz, 2000000));
 }
 
 static void atmci_set_timeout(struct atmel_mci *host,


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