[XS] Change in coreboot[main]: soc/intel/adl: Prevent unconditional legacy COM ports initialization

[Subrata Banik (Code Review)]

Subrata Banik has submitted this change. ( https://review.coreboot.org/c/coreboot/+/84080?usp=email )

Change subject: soc/intel/adl: Prevent unconditional legacy COM ports initialization
......................................................................

soc/intel/adl: Prevent unconditional legacy COM ports initialization

This patch eliminates the LPC_IOE_COMA_EN and LPC_IOE_COMB_EN IO enables
from the io_enables variable in the pch_early_iorange_init() function
because lpc_io_setup_comm_a_b() is intended to activate legacy COM
ports like COM-A (0x3F8 - 0x3FF) and COM_B (0x2F8 - 0x2FF).

These COM ports are being activated unconditionally, which is
undesirable for the Intel Alder Lake platform and causes traffic over
the IO bus.

As a result, this code is being removed and platforms that select
DRIVERS_UART_8250IO can activate legacy COM ports.

BUG=b:354066052
TEST=Able to boot google/redrix to the operating system and confirm
that there was no traffic over legacy COMs while being monitored
using the eSPI analyzer.

Change-Id: I7a6e38bd151f823d37c07ee89a800489122cc209
Signed-off-by: Subrata Banik 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/84080
Reviewed-by: Eric Lai 
Reviewed-by: Dinesh Gehlot 
Tested-by: build bot (Jenkins) 
---
M src/soc/intel/alderlake/bootblock/pch.c
1 file changed, 1 insertion(+), 2 deletions(-)

Approvals:
  Dinesh Gehlot: Looks good to me, approved
  Eric Lai: Looks good to me, approved
  build bot (Jenkins): Verified

diff --git a/src/soc/intel/alderlake/bootblock/pch.c b/src/soc/intel/alderlake/bootblock/pch.c
index 9041052..0115348 100644
--- a/src/soc/intel/alderlake/bootblock/pch.c
+++ b/src/soc/intel/alderlake/bootblock/pch.c
@@ -98,8 +98,7 @@

void pch_early_iorange_init(void)
 {
-	uint16_t io_enables = LPC_IOE_COMA_EN | LPC_IOE_COMB_EN |
-			      LPC_IOE_LPT_EN | LPC_IOE_FDD_EN |
+	uint16_t io_enables = LPC_IOE_LPT_EN | LPC_IOE_FDD_EN |
    		      LPC_IOE_LGE_200 | LPC_IOE_HGE_208 |
    		      LPC_IOE_KBC_60_64 | LPC_IOE_EC_62_66 |
    		      LPC_IOE_SUPERIO_2E_2F | LPC_IOE_EC_4E_4F;