superio/ite: delay PWRGD3 during resume

According to the IT8728F datasheet it is possible to add an extra delay
between 3VSBSW# being set and PWRGD3 being set during resume from
Suspend-to-RAM. This is enabled in the special function selection
register, the default being 0.

This is also useful for the IT8720F although this chip does not have the
PWRGD3 output. On the corresponding pin it has PWROK2, which the setting
then seems to apply to.

The datasheet for the IT8720F marks the corresponding bit as reserved,
but the vendor BIOS of an Acer Aspire M3800 sets it anyway. Without
setting the bit, coreboot fails to resume from S3. Oscilloscope
measurements have shown that setting the bit increases the delay between
3VSBSW# being set and PWROK2 being set from around 1 us to 140 ms. The
actual use of PWROK2 on the board design is unclear - the only
destination it seems to reach is a pin header near the SuperIO marked as
"GPIO1".

Signed-off-by: Michael Büchler <michael.buechler@posteo.net>
Change-Id: I51cbf2470dc2b840a647a20090acb5a0cf4f4025
Reviewed-on: https://review.coreboot.org/c/coreboot/+/44639
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Held <felix-coreboot@felixheld.de>

2 files changed, 28 insertions, 0 deletions

diff --git a/src/superio/ite/common/early_serial.c b/src/superio/ite/common/early_serial.c
index d19548ebca..48e414b0da 100644
--- a/src/superio/ite/common/early_serial.c
+++ b/src/superio/ite/common/early_serial.c
@@ -95,6 +95,33 @@ void ite_enable_3vsbsw(pnp_devfn_t dev)
 }
 
 /*
+ *
+ * LDN 7, reg 0x2a, bit 0 - delay PWRGD3 rising edge after 3VSBSW# rising edge
+ * This can be needed for S3 resume.
+ * Documented in IT8728F V0.4.2 but also applies to IT8720F where it is marked
+ * as reserved.
+ *
+ * Delay PWRGD3 assertion after setting 3VSBSW#.
+ * 0: There will be no extra delay before PWRGD3 is set.
+ * 1: The delay after 3VSBSW# rising edge before PWRGD3 is set is increased.
+ *
+ * in romstage.c
+ * #define GPIO_DEV PNP_DEV(0x2e, ITE_GPIO)
+ * and pass: GPIO_DEV
+ */
+
+void ite_delay_pwrgd3(pnp_devfn_t dev)
+{
+	u8 tmp;
+	pnp_enter_conf_state(dev);
+	pnp_set_logical_device(dev);
+	tmp = pnp_read_config(dev, ITE_CONFIG_REG_MFC);
+	tmp |= 0x01;
+	pnp_write_config(dev, ITE_CONFIG_REG_MFC, tmp);
+	pnp_exit_conf_state(dev);
+}
+
+/*
  * in romstage.c
  * #define GPIO_DEV PNP_DEV(0x2e, ITE_GPIO)
  * and pass: GPIO_DEV
diff --git a/src/superio/ite/common/ite.h b/src/superio/ite/common/ite.h
index a0c20ff8e1..3e9b50289a 100644
--- a/src/superio/ite/common/ite.h
+++ b/src/superio/ite/common/ite.h
@@ -15,6 +15,7 @@ void ite_enable_serial(pnp_devfn_t dev, u16 iobase);
 /* Some boards need to init wdt+gpio's very early */
 void ite_reg_write(pnp_devfn_t dev, u8 reg, u8 value);
 void ite_enable_3vsbsw(pnp_devfn_t dev);
+void ite_delay_pwrgd3(pnp_devfn_t dev);
 void ite_kill_watchdog(pnp_devfn_t dev);
 
 void pnp_enter_conf_state(pnp_devfn_t dev);