Change in coreboot[master]: mb/google/dedede/var/blipper: Configure I2C times for touchpad/touchp...

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/54249 )

Change subject: mb/google/dedede/var/blipper: Configure I2C times for touchpad/touchpanel/codec
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mb/google/dedede/var/blipper: Configure I2C times for touchpad/touchpanel/codec

Configure I2C rise/fall time in device tree to ensure I2C
CLK runs accurately at I2C_SPEED_FAST (<400 kHz).

Measured I2C frequency changes are just as below after tuning:
touchpad: 434kHz ---> 391kHz
touchpanel: 439kHz ---> 382kHz
audio codec RT5682: 445kHz ---> 385kHz

BUG=b:187555396
BRANCH=dedede
TEST=Build and check after tuning I2C clock is under 400 kHz

Signed-off-by: Tao Xia 
Change-Id: I8438e37be49f8a74f53fd8460110dac1a3f06993
Reviewed-on: https://review.coreboot.org/c/coreboot/+/54249
Tested-by: build bot (Jenkins) 
Reviewed-by: Karthik Ramasubramanian 
---
M src/mainboard/google/dedede/variants/blipper/overridetree.cb
1 file changed, 6 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Karthik Ramasubramanian: Looks good to me, approved

diff --git a/src/mainboard/google/dedede/variants/blipper/overridetree.cb b/src/mainboard/google/dedede/variants/blipper/overridetree.cb
index df3f9dd..a5a7e48 100644
--- a/src/mainboard/google/dedede/variants/blipper/overridetree.cb
+++ b/src/mainboard/google/dedede/variants/blipper/overridetree.cb
@@ -21,18 +21,24 @@
    	},
    	.i2c[0] = {
    		.speed = I2C_SPEED_FAST,
+			.rise_time_ns = 247,
+			.fall_time_ns = 11,
    	},
    	.i2c[1] = {
    		.speed = I2C_SPEED_FAST,
    	},
    	.i2c[2] = {
    		.speed = I2C_SPEED_FAST,
+			.rise_time_ns = 175,
+			.fall_time_ns = 20,
    	},
    	.i2c[3] = {
    		.speed = I2C_SPEED_FAST,
    	},
    	.i2c[4] = {
    		.speed = I2C_SPEED_FAST,
+			.rise_time_ns = 99,
+			.fall_time_ns = 7,
    	},
    }"