MIPS: ath79: Fix the ar724x clock calculation
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@gmail.com>
Signed-off-by: Alban Bedel <albeu@free.fr> (Fixed the commit log message)
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12870/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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 @@
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;