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authorValentin Longchamp <valentin.longchamp@keymile.com>2015-02-10 16:46:33 +0100
committerWolfram Sang <wsa@the-dreams.de>2015-03-15 11:04:54 +0100
commit8ce795cb0c6b8214779c4a220781a26f096e4442 (patch)
treeec29263e34e460c18806c9db94bb10c94c69f44b /drivers/i2c
parent913b1d85cdde5f1fc081aa84f548270a15027abb (diff)
downloadlinux-8ce795cb0c6b8214779c4a220781a26f096e4442.tar.bz2
i2c: mpc: assign the correct prescaler from SVR
For the 85xx platforms, the source clock for the i2c-mpc can change from one SoC to another. This is documented in the AN2919 "Determining the I2C Frequency Divider Ratio for SCL" by Freescale. Not taking this into account can lead to the output SCL frequency to by off by an offset. It was observed on the P2041 from the QorIQ family. This patch fixes this problem by setting the prescaler value to the appropriate value when required. The SoCs that required a different prescaler than 1 are identified by reading out the SVR as discussed in http://thread.gmane.org/gmane.linux.drivers.devicetree/94247/focus=20556 Signed-off-by: Valentin Longchamp <valentin.longchamp@keymile.com> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Diffstat (limited to 'drivers/i2c')
-rw-r--r--drivers/i2c/busses/i2c-mpc.c30
1 files changed, 29 insertions, 1 deletions
diff --git a/drivers/i2c/busses/i2c-mpc.c b/drivers/i2c/busses/i2c-mpc.c
index c74cc2be613b..dc03a9164772 100644
--- a/drivers/i2c/busses/i2c-mpc.c
+++ b/drivers/i2c/busses/i2c-mpc.c
@@ -29,6 +29,7 @@
#include <linux/delay.h>
#include <asm/mpc52xx.h>
+#include <asm/mpc85xx.h>
#include <sysdev/fsl_soc.h>
#define DRV_NAME "mpc-i2c"
@@ -346,6 +347,33 @@ static u32 mpc_i2c_get_sec_cfg_8xxx(void)
return val;
}
+static u32 mpc_i2c_get_prescaler_8xxx(void)
+{
+ /* mpc83xx and mpc82xx all have prescaler 1 */
+ u32 prescaler = 1;
+
+ /* mpc85xx */
+ if (pvr_version_is(PVR_VER_E500V1) || pvr_version_is(PVR_VER_E500V2)
+ || pvr_version_is(PVR_VER_E500MC)
+ || pvr_version_is(PVR_VER_E5500)
+ || pvr_version_is(PVR_VER_E6500)) {
+ unsigned int svr = mfspr(SPRN_SVR);
+
+ if ((SVR_SOC_VER(svr) == SVR_8540)
+ || (SVR_SOC_VER(svr) == SVR_8541)
+ || (SVR_SOC_VER(svr) == SVR_8560)
+ || (SVR_SOC_VER(svr) == SVR_8555)
+ || (SVR_SOC_VER(svr) == SVR_8610))
+ /* the above 85xx SoCs have prescaler 1 */
+ prescaler = 1;
+ else
+ /* all the other 85xx have prescaler 2 */
+ prescaler = 2;
+ }
+
+ return prescaler;
+}
+
static int mpc_i2c_get_fdr_8xxx(struct device_node *node, u32 clock,
u32 prescaler, u32 *real_clk)
{
@@ -363,7 +391,7 @@ static int mpc_i2c_get_fdr_8xxx(struct device_node *node, u32 clock,
if (of_device_is_compatible(node, "fsl,mpc8544-i2c"))
prescaler = mpc_i2c_get_sec_cfg_8xxx() ? 3 : 2;
if (!prescaler)
- prescaler = 1;
+ prescaler = mpc_i2c_get_prescaler_8xxx();
divider = fsl_get_sys_freq() / clock / prescaler;