Change in coreboot[master]: soc/amd/common/block/spi: Support fast speed override

[Karthik Ramasubramanian (Code Review)]

Attention is currently required from: Jason Glenesk, Raul Rangel, Marshall Dawson, Felix Held.
Karthik Ramasubramanian has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/58116 )

Change subject: soc/amd/common/block/spi: Support fast speed override
......................................................................

soc/amd/common/block/spi: Support fast speed override

Add support to override SPI ROM fast speed based on board version. This
will allow boards to start at lower speeds during bringup and then
switch to higher speeds after assessing the signal integrity. Also
implement a default no-op override.

BUG=None
TEST=Build and boot to OS in Guybrush. Perform S5->S0, G3->S0, warm
reset and suspend/resume cycles for 50 iterations each.

Signed-off-by: Karthikeyan Ramasubramanian 
Change-Id: Ia8ff3b3bdb53fee142527ae63aa7785945909304
---
M src/soc/amd/common/block/include/amdblocks/spi.h
M src/soc/amd/common/block/spi/fch_spi.c
2 files changed, 7 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/16/58116/1

diff --git a/src/soc/amd/common/block/include/amdblocks/spi.h b/src/soc/amd/common/block/include/amdblocks/spi.h
index eaea0f7..35a3782 100644
--- a/src/soc/amd/common/block/include/amdblocks/spi.h
+++ b/src/soc/amd/common/block/include/amdblocks/spi.h
@@ -117,4 +117,5 @@
 void spi_write32(uint8_t reg, uint32_t val);

void fch_spi_config_modes(void);
+void mainboard_spi_fast_speed_override(uint8_t *fast_speed);
 #endif /* AMD_BLOCK_SPI_H */
diff --git a/src/soc/amd/common/block/spi/fch_spi.c b/src/soc/amd/common/block/spi/fch_spi.c
index 51787fae..6757f36 100644
--- a/src/soc/amd/common/block/spi/fch_spi.c
+++ b/src/soc/amd/common/block/spi/fch_spi.c
@@ -50,6 +50,11 @@
    printk(BIOS_DEBUG, "SPI Read Mode: %s\n", read_mode_str[DECODE_SPI_READ_MODE(val32)]);
 }

+void __weak mainboard_spi_fast_speed_override(uint8_t *unused)
+{
+	/* No overriding SPI speeds. */
+}
+
 static uint8_t lower_speed(uint8_t speed1, uint8_t speed2)
 {
    uint8_t speeds[] = {SPI_SPEED_800K, SPI_SPEED_16M, SPI_SPEED_22M,
@@ -102,6 +107,7 @@
    	read_mode = CONFIG_EFS_SPI_READ_MODE;
    	fast_speed = CONFIG_EFS_SPI_SPEED;
    }
+	mainboard_spi_fast_speed_override(&fast_speed);

if (fast_speed != CONFIG_EFS_SPI_SPEED) {
    	normal_speed = lower_speed(normal_speed, fast_speed);