mb/google/skyrim: override winterhold PCIe config

Winterhold boards populate either NVMe or eMMC, but not both.
This means that there is always one link that is unpopulated. The PCIe
configuration code takes longer to verify that a link is unpopulated
than to just train the link, so this slows down the boot by roughly
80ms vs the case when the device is present. Not training the device
at all lowers boot time by another 20ms, for a total of 100ms saved.

Looking at the NVMe CLKREQ signal before initializing the ports allows
us to identify which device is populated and only initialize that
device.

BUG=b:271569628
TEST=Boot Whiterun and eMMC or NVMe correctly work, boot time is lower.
BRANCH=skyrim

Signed-off-by: Martin Roth <gaumless@gmail.com>
Change-Id: I0b87f5e968cd1c87e62a1c0fbdee1fc0723f655d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/73441
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>

src/mainboard/google/skyrim/Kconfig

@@ -124,6 +124,8 @@ config VARIANT_DIR
 
 config USE_VARIANT_DXIO_DESCRIPTOR
 	bool
+	default y if BOARD_GOOGLE_WINTERHOLD
+	default n
 	help
 	  Enable this to allow a variant to override the dxio descriptor values
 	  in port_descriptors.c

src/mainboard/google/skyrim/variants/baseboard/gpio.c

@@ -201,6 +201,8 @@ static const struct soc_amd_gpio romstage_gpio_table[] = {
 	PAD_NFO(GPIO_27, PCIE_RST1_L, HIGH),
 	/* SSD_AUX_RESET_L */
 	PAD_GPO(GPIO_6, HIGH),
+	/* CLK_REQ0_L / SSD */
+	PAD_NF(GPIO_92, CLK_REQ0_L, PULL_NONE),
 	/* Enable touchscreen, hold in reset */
 	/* EN_PP3300_TCHSCR */
 	PAD_GPO(GPIO_131, HIGH),

src/mainboard/google/skyrim/variants/winterhold/Makefile.inc

@@ -2,4 +2,7 @@
 
 subdirs-y += ./memory
 
+romstage-y += port_descriptors.c
+
 ramstage-y += gpio.c
+ramstage-y += port_descriptors.c

src/mainboard/google/skyrim/variants/winterhold/port_descriptors.c

@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <baseboard/variants.h>
+#include <console/console.h>
+#include <gpio.h>
+#include <soc/platform_descriptors.h>
+#include <types.h>
+
+static const fsp_dxio_descriptor emmc_dxio_descriptors[] = {
+	{
+		/* WLAN */
+		.engine_type = PCIE_ENGINE,
+		.port_present = true,
+		.start_logical_lane = 0,
+		.end_logical_lane = 0,
+		.device_number = PCI_SLOT(WLAN_DEVFN),
+		.function_number = PCI_FUNC(WLAN_DEVFN),
+		.link_speed_capability = GEN3,
+		.turn_off_unused_lanes = true,
+		.link_aspm = ASPM_L1,
+		.link_aspm_L1_1 = true,
+		.link_aspm_L1_2 = true,
+		.clk_req = CLK_REQ2,
+	},
+	{
+		/* eMMC */
+		.engine_type = PCIE_ENGINE,
+		.port_present = true,
+		.start_logical_lane = 1,
+		.end_logical_lane = 1,
+		.device_number = PCI_SLOT(SD_DEVFN),
+		.function_number = PCI_FUNC(SD_DEVFN),
+		.link_speed_capability = GEN3,
+		.turn_off_unused_lanes = true,
+		.link_aspm = ASPM_L1,
+		.link_aspm_L1_1 = true,
+		.link_aspm_L1_2 = true,
+		.gpio_group_id = GPIO_27,
+		.clk_req = CLK_REQ1,
+	},
+};
+
+static const fsp_dxio_descriptor nvme_dxio_descriptors[] = {
+	{
+		/* WLAN */
+		.engine_type = PCIE_ENGINE,
+		.port_present = true,
+		.start_logical_lane = 0,
+		.end_logical_lane = 0,
+		.device_number = PCI_SLOT(WLAN_DEVFN),
+		.function_number = PCI_FUNC(WLAN_DEVFN),
+		.link_speed_capability = GEN3,
+		.turn_off_unused_lanes = true,
+		.link_aspm = ASPM_L1,
+		.link_aspm_L1_1 = true,
+		.link_aspm_L1_2 = true,
+		.clk_req = CLK_REQ2,
+	},
+	{
+		/* SSD */
+		.engine_type = PCIE_ENGINE,
+		.port_present = true,
+		.start_logical_lane = 2,
+		.end_logical_lane = 3,
+		.device_number = PCI_SLOT(NVME_DEVFN),
+		.function_number = PCI_FUNC(NVME_DEVFN),
+		.link_speed_capability = GEN3,
+		.turn_off_unused_lanes = true,
+		.link_aspm = ASPM_L1,
+		.link_aspm_L1_1 = true,
+		.link_aspm_L1_2 = true,
+		.gpio_group_id = GPIO_6,
+		.clk_req = CLK_REQ0,
+	},
+};
+
+#define NVME_CLKREQ_GPIO 92
+void variant_get_dxio_descriptor(const fsp_dxio_descriptor **dxio_descs, size_t *dxio_num)
+{
+	/*
+	 * We can determine if a device is populated based on the state of the clkreq
+	 * signal. If the device is present, the clkreq is held low by the device. If
+	 * no device is present, clkreq is pulled high by an external pull-up.
+	 *
+	 * This allows checking the state of the NVMe device clkreq signal and enabling
+	 * either eMMC or NVMe based on that.
+	 */
+	if (gpio_get(NVME_CLKREQ_GPIO)) {
+		printk(BIOS_DEBUG, "Enabling eMMC.\n");
+		*dxio_num = ARRAY_SIZE(emmc_dxio_descriptors);
+		*dxio_descs = emmc_dxio_descriptors;
+	} else {
+		printk(BIOS_DEBUG, "Enabling NVMe.\n");
+		*dxio_num = ARRAY_SIZE(nvme_dxio_descriptors);
+		*dxio_descs = nvme_dxio_descriptors;
+	}
+}