linux-kernel - [PATCH 3.10 13/52] ARM: at91: sama5d3: reduce TWI internal clock frequency

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Date:	Tue, 10 Dec 2013 00:00:46 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	Nicolas Ferre <nicolas.ferre@...el.com>
Subject: [PATCH 3.10 13/52] ARM: at91: sama5d3: reduce TWI internal clock frequency

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

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

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

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@...el.com>
Acked-by: Wolfram Sang <wsa@...-dreams.de>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm/mach-at91/sama5d3.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- 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",


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