From eda13db4e93bda57d73a5b71229588238b5e1e1b Mon Sep 17 00:00:00 2001 From: Werner Zeh Date: Mon, 7 Nov 2022 15:15:58 +0100 Subject: mb/siemens/mc_ehl2: Add dummy I2C devices to limit the I2C speed in OS In Linux, the I2C speed defaults to 400 kHz if there is no device registered in ACPI which requests a different speed. Due to board limitations (layout, bus load), 400 kHz are too fast which results in a timing violation. Therefore, add a dummy I2C device to both used I2C buses (I2C1 and I2C2) with a speed of 100 kHz. This will limit the bus speed in Linux accordingly. Change-Id: I507c53c9ec7f763cef18903609231b1a66ed98fa Signed-off-by: Werner Zeh Reviewed-on: https://review.coreboot.org/c/coreboot/+/69306 Tested-by: build bot (Jenkins) Reviewed-by: Mario Scheithauer --- .../siemens/mc_ehl/variants/mc_ehl2/devicetree.cb | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/mainboard/siemens/mc_ehl/variants/mc_ehl2/devicetree.cb b/src/mainboard/siemens/mc_ehl/variants/mc_ehl2/devicetree.cb index 4109ec9157..d5d12777ec 100644 --- a/src/mainboard/siemens/mc_ehl/variants/mc_ehl2/devicetree.cb +++ b/src/mainboard/siemens/mc_ehl/variants/mc_ehl2/devicetree.cb @@ -144,8 +144,21 @@ chip soc/intel/elkhartlake register "cap_charge" = "CHARGE_OFF" device i2c 0x52 on end # RTC RV3028-C7 end + # Add dummy I2C device to limit BUS speed to 100 kHz in OS + chip drivers/i2c/generic + register "hid" = ""PRP0001"" + register "speed" = "I2C_SPEED_STANDARD" + device i2c 0x7f on end + end + end + device pci 15.2 on # I2C2 + # Add dummy I2C device to limit BUS speed to 100 kHz in OS + chip drivers/i2c/generic + register "hid" = ""PRP0001"" + register "speed" = "I2C_SPEED_STANDARD" + device i2c 0x7f on end + end end - device pci 15.2 on end # I2C2 device pci 15.3 on end # I2C3 device pci 16.0 hidden end # Management Engine Interface 1 -- cgit v1.2.3