linux-kernel - [PATCH 1/2] MIPS: ath79: Fix the ar724x clock calculation

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Message-Id: <1448193785-31072-1-git-send-email-albeu@free.fr>
Date:	Sun, 22 Nov 2015 13:03:04 +0100
From:	Alban Bedel <albeu@...e.fr>
To:	linux-mips@...ux-mips.org
Cc:	Ralf Baechle <ralf@...ux-mips.org>,
	Weijie Gao <hackpascal@...il.com>,
	linux-kernel@...r.kernel.org, Alban Bedel <albeu@...e.fr>
Subject: [PATCH 1/2] MIPS: ath79: Fix the ar724x clock calculation

From: Weijie Gao <hackpascal@...il.com>

According to the AR7242 datasheet section 2.8, AR724X CPUs use a 40MHz
input clock as the REF_CLK instead of 5MHz.

The correct CPU PLL calculation procedure is as follows:
CPU_PLL = (FB * REF_CLK) / REF_DIV / 2.

This patch is compatible with the current calculation procedure with
default FB and REF_DIV values.

Tested on AR7240, AR7241 and AR7242.

Signed-off-by: Weijie Gao <hackpascal@...il.com>
Signed-off-by: Alban Bedel <albeu@...e.fr>
[albeu@...e.fr: Fixed the commit log message]
---
 arch/mips/ath79/clock.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/mips/ath79/clock.c b/arch/mips/ath79/clock.c
index eb5117c..ed28465 100644
--- a/arch/mips/ath79/clock.c
+++ b/arch/mips/ath79/clock.c
@@ -26,7 +26,7 @@
 #include "common.h"
 
 #define AR71XX_BASE_FREQ	40000000
-#define AR724X_BASE_FREQ	5000000
+#define AR724X_BASE_FREQ	40000000
 #define AR913X_BASE_FREQ	5000000
 
 static struct clk *clks[3];
@@ -103,8 +103,8 @@ static void __init ar724x_clocks_init(void)
 	div = ((pll >> AR724X_PLL_FB_SHIFT) & AR724X_PLL_FB_MASK);
 	freq = div * ref_rate;
 
-	div = ((pll >> AR724X_PLL_REF_DIV_SHIFT) & AR724X_PLL_REF_DIV_MASK);
-	freq *= div;
+	div = ((pll >> AR724X_PLL_REF_DIV_SHIFT) & AR724X_PLL_REF_DIV_MASK) * 2;
+	freq /= div;
 
 	cpu_rate = freq;
 
-- 
2.0.0

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