[coreboot-gerrit] Change in coreboot[master]: soc/intel/tigerlake: Set default USB3 de-emphasis to -3.5dB

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/43831 )

Change subject: soc/intel/tigerlake: Set default USB3 de-emphasis to -3.5dB
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soc/intel/tigerlake: Set default USB3 de-emphasis to -3.5dB

The HSIO tuning guide recommendation for the default USB3 settings is to
have de-emphasis set to -3.5dB with the equation 20*log(X/64).  0x29 results
in a value close to -3.5dB and it is the value that was used for the default
on past platforms so I used it here as well.

BUG=b:160721468
TEST=Ensure WWAN device does not disconnect during use.

Change-Id: Ia594996cb55523dacce0d4bef98cc217321c62de
Signed-off-by: Duncan Laurie 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43831
Tested-by: build bot (Jenkins) 
Reviewed-by: Angel Pons 
---
M src/soc/intel/tigerlake/include/soc/usb.h
1 file changed, 1 insertion(+), 1 deletion(-)

Approvals:
  build bot (Jenkins): Verified
  Angel Pons: Looks good to me, approved

diff --git a/src/soc/intel/tigerlake/include/soc/usb.h b/src/soc/intel/tigerlake/include/soc/usb.h
index 247b0ba..d4836c9 100644
--- a/src/soc/intel/tigerlake/include/soc/usb.h
+++ b/src/soc/intel/tigerlake/include/soc/usb.h
@@ -132,7 +132,7 @@
 #define USB3_PORT_DEFAULT(pin) { \
    .enable           = 1, \
    .ocpin            = (pin), \
-	.tx_de_emp        = 0x0, \
+	.tx_de_emp        = 0x29, \
    .tx_downscale_amp = 0x00, \
 }