This is a note to let you know that I've just added the patch titled
i2c: rk3x: fix divisor calculation for SCL frequency
to the 3.16-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
i2c-rk3x-fix-divisor-calculation-for-scl-frequency.patch
and it can be found in the queue-3.16 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From b4a7bd7a386dc6b0bb49cb47614e06e8295d495a Mon Sep 17 00:00:00 2001
From: addy ke <[email protected]>
Date: Mon, 8 Sep 2014 11:38:25 +0800
Subject: i2c: rk3x: fix divisor calculation for SCL frequency
From: addy ke <[email protected]>
commit b4a7bd7a386dc6b0bb49cb47614e06e8295d495a upstream.
I2C_CLKDIV register descripted in the previous version of
RK3x chip manual is incorrect. Plus 1 is required.
The correct formula:
- T(SCL_HIGH) = T(PCLK) * (CLKDIVH + 1) * 8
- T(SCL_LOW) = T(PCLK) * (CLKDIVL + 1) * 8
- (SCL Divsor) = 8 * ((CLKDIVL + 1) + (CLKDIVH + 1))
- SCL = PCLK / (CLK Divsor)
It will be updated to the latest version of chip manual.
Signed-off-by: Addy Ke <[email protected]>
Reviewed-by: Doug Anderson <[email protected]>
Signed-off-by: Wolfram Sang <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/i2c/busses/i2c-rk3x.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
--- a/drivers/i2c/busses/i2c-rk3x.c
+++ b/drivers/i2c/busses/i2c-rk3x.c
@@ -433,12 +433,11 @@ static void rk3x_i2c_set_scl_rate(struct
unsigned long i2c_rate = clk_get_rate(i2c->clk);
unsigned int div;
- /* SCL rate = (clk rate) / (8 * DIV) */
- div = DIV_ROUND_UP(i2c_rate, scl_rate * 8);
-
- /* The lower and upper half of the CLKDIV reg describe the length of
- * SCL low & high periods. */
- div = DIV_ROUND_UP(div, 2);
+ /* set DIV = DIVH = DIVL
+ * SCL rate = (clk rate) / (8 * (DIVH + 1 + DIVL + 1))
+ * = (clk rate) / (16 * (DIV + 1))
+ */
+ div = DIV_ROUND_UP(i2c_rate, scl_rate * 16) - 1;
i2c_writel(i2c, (div << 16) | (div & 0xffff), REG_CLKDIV);
}
Patches currently in stable-queue which might be from [email protected] are
queue-3.16/i2c-rk3x-fix-divisor-calculation-for-scl-frequency.patch
queue-3.16/i2c-rk3x-fix-bug-that-cause-transfer-fails-in-master-receive-mode.patch
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