New patch to review for coreboot: mainboard/google/reef: Tune i2c frequency to under 400 Khz

[Tim Chen]

Tim Chen ([e-mail]) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/18284

-gerrit

commit 8fca0ab3999413daeadb990aca4cb5fcad41b366
Author: Tim Chen 
Date:   Fri Feb 3 16:57:39 2017 +0800

mainboard/google/reef: Tune i2c frequency to under 400 Khz

tune i2c devices clk for reef:
    I2C0: audio
    I2C2: TPM H1
    I2C4: elan touchpad

BUG=chrome-os-partner:62593
    BRANCH=master
    TEST=emerge-reef coreboot chromeos-bootimage, and measured on EVT.
    audio:
      Freq. 393.1kHz
    TPM H1:
      Freq. 369.5kHz
    elan touchpad:
      Freq. 397.0kHz

Change-Id: If27b7a1333d5f1e14c850a0dfb3c6eb90f0072fc
---
 src/mainboard/google/reef/variants/baseboard/devicetree.cb | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/mainboard/google/reef/variants/baseboard/devicetree.cb b/src/mainboard/google/reef/variants/baseboard/devicetree.cb
index 2ccf277..e40bfee 100644
--- a/src/mainboard/google/reef/variants/baseboard/devicetree.cb
+++ b/src/mainboard/google/reef/variants/baseboard/devicetree.cb
@@ -76,16 +76,16 @@ chip soc/intel/apollolake
    # Enable I2C0 for audio codec at 400kHz
    register "i2c[0]" = "{
    	.speed = I2C_SPEED_FAST,
-		.rise_time_ns = 104,
-		.fall_time_ns = 52,
+		.rise_time_ns = 44,
+		.fall_time_ns = 22,
    }"

# Enable I2C2 bus early for TPM at 400kHz
    register "i2c[2]" = "{
    	.early_init = 1,
    	.speed = I2C_SPEED_FAST,
-		.rise_time_ns = 57,
-		.fall_time_ns = 28,
+		.rise_time_ns = 30,
+		.fall_time_ns = 15,
    }"

# touchscreen at 400kHz
@@ -98,8 +98,8 @@ chip soc/intel/apollolake
    # trackpad at 400kHz
    register "i2c[4]" = "{
    	.speed = I2C_SPEED_FAST,
-		.rise_time_ns = 114,
-		.fall_time_ns = 164,
+		.rise_time_ns = 57,
+		.fall_time_ns = 82,
    }"

# digitizer at 400kHz