[3.11.y.z extended stable] Patch "ARM: at91: sama5d3: reduce TWI internal clock frequency" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ARM: at91: sama5d3: reduce TWI internal clock frequency

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 32a3cdda4f3f6d2ed5424080ab66cf02f5dbe952 Mon Sep 17 00:00:00 2001
From: Ludovic Desroches <ludovic.desroches at atmel.com>
Date: Fri, 22 Nov 2013 17:08:43 +0100
Subject: ARM: at91: sama5d3: reduce TWI internal clock frequency

commit 58e7b1d5826ac6a64b1101d8a70162bc084a7d1e upstream.

With some devices, transfer hangs during I2C frame transmission. This issue
disappears when reducing the internal frequency of the TWI IP. Even if it is
indicated that internal clock max frequency is 66MHz, it seems we have
oversampling on I2C signals making TWI believe that a transfer in progress
is done.

This fix has no impact on the I2C bus frequency.

Signed-off-by: Ludovic Desroches <ludovic.desroches at atmel.com>
Acked-by: Wolfram Sang <wsa at the-dreams.de>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre at atmel.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/arm/mach-at91/sama5d3.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-at91/sama5d3.c b/arch/arm/mach-at91/sama5d3.c
index 3ea8642..a28873f 100644
--- a/arch/arm/mach-at91/sama5d3.c
+++ b/arch/arm/mach-at91/sama5d3.c
@@ -95,19 +95,19 @@ static struct clk twi0_clk = {
 	.name		= "twi0_clk",
 	.pid		= SAMA5D3_ID_TWI0,
 	.type		= CLK_TYPE_PERIPHERAL,
-	.div		= AT91_PMC_PCR_DIV2,
+	.div		= AT91_PMC_PCR_DIV8,
 };
 static struct clk twi1_clk = {
 	.name		= "twi1_clk",
 	.pid		= SAMA5D3_ID_TWI1,
 	.type		= CLK_TYPE_PERIPHERAL,
-	.div		= AT91_PMC_PCR_DIV2,
+	.div		= AT91_PMC_PCR_DIV8,
 };
 static struct clk twi2_clk = {
 	.name		= "twi2_clk",
 	.pid		= SAMA5D3_ID_TWI2,
 	.type		= CLK_TYPE_PERIPHERAL,
-	.div		= AT91_PMC_PCR_DIV2,
+	.div		= AT91_PMC_PCR_DIV8,
 };
 static struct clk mmc0_clk = {
 	.name		= "mci0_clk",
--
1.8.3.2