Change in coreboot[master]: drivers/tpm: Force enable long IRQ pulses for Ti50 versions under 0.15.

[Paul Fagerburg (Code Review)]

Paul Fagerburg has submitted this change. ( https://review.coreboot.org/c/coreboot/+/63160 )

Change subject: drivers/tpm: Force enable long IRQ pulses for Ti50 versions under 0.15.
......................................................................

drivers/tpm: Force enable long IRQ pulses for Ti50 versions under 0.15.

Only Cr50 versions starting at 0.5.5 support long IRQ pulses, so this
feature is enabled based on the value of the board_cfg register (see
CB:61722).

However, Ti50 versions below 0.0.15 don't support the board_cfg
register, and trying to access it will cause I2C errors (see CB:63011).
Also, all Ti50 versions only support long IRQ pulses. Therefore, add a
workaround to force enable long IRQ pulses for boards using Ti50
versions under 0.0.15, instead of enabling it based on board_cfg. This
workaround will be removed once all Ti50 stocks are updated to 0.0.15 or
higher.

BUG=b:225941781
TEST=Boot nivviks and nereid to OS with Ti50 0.0.14 and check there are
none of these I2C errors:
[ERROR]  I2C stop bit not received
[ERROR]  cr50_i2c_read: Address write failed
[ERROR]  cr50_i2c_tis_status: Failed to read status

Change-Id: Iaba71461d8ec79e8d6efddbd505339cdf1176485
Signed-off-by: Reka Norman 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63160
Reviewed-by: Eric Lai 
Reviewed-by: Kangheui Won 
Tested-by: build bot (Jenkins) 
---
M src/drivers/tpm/cr50.c
1 file changed, 8 insertions(+), 0 deletions(-)

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

diff --git a/src/drivers/tpm/cr50.c b/src/drivers/tpm/cr50.c
index 1d6c691..4ab01fb 100644
--- a/src/drivers/tpm/cr50.c
+++ b/src/drivers/tpm/cr50.c
@@ -142,6 +142,14 @@

bool cr50_is_long_interrupt_pulse_enabled(void)
 {
+	/*
+	 * Ti50 FW versions under 0.15 don't support the board cfg register,
+	 * and all Ti50 versions only support long IRQ pulses.
+	 * TODO: Remove this after all Ti50 stocks uprev to 0.15 or above.
+	 */
+	if (CONFIG(MAINBOARD_NEEDS_I2C_TI50_WORKAROUND))
+		return true;
+
    return !!(cr50_get_board_cfg() & CR50_BOARD_CFG_100US_READY_PULSE);
 }