mb/google/zork: Add support for WiFi power sequencing

This change replaces variant_wifi_romstage_gpio_table() with
variant_pcie_power_reset_configure() to handle the reset and power
sequencing for WiFi devices pre- and post- v3 version of schematics.

These are the requirements that need to be satisfied:
1. As per PCI Express M.2 Specification Revision 3.0,
Version 1.2, Section 3.1.4 "Power-up Timing", PERST# should stay
disabled until `TPVPGL` time duration after device power has
stabilized.  Value of TPVPGL is implementation specific.
2. For Intel WiFi chip, it is known to get into a bad state if the
above requirement is violated and hence requires a power cycle.
3. On pre-v3 schematics:
  - For both dalboz and trembyle references, GPIO42 drives
  WIFI_AUX_RESET_L which is pulled up to PP3300_WIFI.
  - For both dalboz and trembyle references, PP3300_WIFI is controlled
  using GPIO29. This pad gets pulled high by default on PWRGOOD
  because of internal pull-up. But, at RESET# it is known to have a
  glitch. When GPIO29 gets pulled high, it causes WIFI_AUX_RESET_L to
  be pulled high as well. This violates the PCIe power sequencing
  requirements. Hence, for pre-v3 schematics on both dalboz and
  trembyle, following sequence needs to be followed:
   a. Assert WIFI_AUX_RESET_L.
   b. Disable power to WiFi.
   c. Wait 10ms to allow WiFi power to go low.
   d. Enable power to WiFi.
   e. Wait 50ms as per PCIe specification.
   f. Deassert WIFI_AUX_RESET_L.
4. On v3 schematics:
   - For trembyle: WIFI_AUX_RESET_L is driven by GPIO86 which has an
   internal PU as well as an external PU to PP3300_WIFI.
   - For dalboz: WIFI_AUX_RESET is driven by GPIO29. This is active
   high and has an internal PU. It also has an external 1K PD to
   overcome internal PU.
   - For both dalboz and trembyle references, PP3300_WIFI is
   controlled by GPIO42 which has an internal PU and external
   PD. Trembyle schematics have a comment saying strong PD of 2.2K but
   the stuffed resistor is a weak one (499K). ON dalboz, it uses a
   weak PD (which doesn't look correct and instead should be a strong
   PD just like trembyle). Having a strong PD ensures that the WiFi
   power is kept disabled when coming out of G3 until coreboot
   configures GPIO42 as high.
   - Thus, for v3 schematics, following sequence needs to be followed:
    a. Assert WIFI_AUX_RESET{_L} signal.
    b. Enable power to WiFi.
    c. Wait 50ms as per PCIe specification.
    d. Deassert WIFI_AUX_RESET{_L} signal.

BUG=b:157686402, b:158257076
TEST=Verified that QCA and AX200 cards both continue working. Tested
QCA on Dalboz and Trembyle. Tested AX200 on morphius.

Signed-off-by: Furquan Shaikh <furquan@google.com>
Change-Id: I532131ee911d5efb5130d8710f3e01578f6c9627
Reviewed-on: https://review.coreboot.org/c/coreboot/+/42738
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

2 files changed, 0 insertions, 29 deletions

diff --git a/src/mainboard/google/zork/variants/berknip/Makefile.inc b/src/mainboard/google/zork/variants/berknip/Makefile.inc
index b1212bcbdd..57e7136ddc 100644
--- a/src/mainboard/google/zork/variants/berknip/Makefile.inc
+++ b/src/mainboard/google/zork/variants/berknip/Makefile.inc
@@ -2,6 +2,4 @@
 
 subdirs-y += ./spd
 
-romstage-y += ./romstage.c
-
 ramstage-y += gpio.c
diff --git a/src/mainboard/google/zork/variants/berknip/romstage.c b/src/mainboard/google/zork/variants/berknip/romstage.c
deleted file mode 100644
index 67ad31c6d8..0000000000
--- a/src/mainboard/google/zork/variants/berknip/romstage.c
+++ /dev/null
@@ -1,27 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-
-#include <stddef.h>
-#include <soc/romstage.h>
-#include <baseboard/variants.h>
-#include <ec/google/chromeec/ec.h>
-
-#include <gpio.h>
-#include <soc/gpio.h>
-#include <variant/gpio.h>
-
-void variant_romstage_entry(void)
-{
-	/* Power the wifi card */
-	gpio_set(EN_PWR_WIFI, 1);
-}
-
-static const struct soc_amd_gpio berknip_gpio_set_wifi[] = {
-	/* EN_PWR_WIFI - Power off. Pull high in romstage.c */
-	PAD_GPO(GPIO_29, LOW),
-};
-
-const struct soc_amd_gpio *variant_wifi_romstage_gpio_table(size_t *size)
-{
-	*size = ARRAY_SIZE(berknip_gpio_set_wifi);
-	return berknip_gpio_set_wifi;
-}