x86: Add low-power subsystem (lpss) support

This subsystem is present on various Intel SoCs.

Add very basic support for taking an lpss device out of reset.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/intel_common/Makefile

@@ -19,6 +19,7 @@ endif
 obj-y += cpu.o
 obj-y += fast_spi.o
 obj-y += lpc.o
+obj-y += lpss.o
 ifndef CONFIG_TARGET_EFI_APP
 obj-$(CONFIG_$(SPL_TPL_)X86_32BIT_INIT) += microcode.o
 ifndef CONFIG_$(SPL_)X86_64

arch/x86/cpu/intel_common/lpss.c

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Special driver to handle of-platdata
+ *
+ * Copyright 2019 Google LLC
+ *
+ * Some code from coreboot lpss.c
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <pci.h>
+#include <asm/io.h>
+#include <asm/lpss.h>
+
+enum {
+	LPSS_RESET_CTL_REG	= 0x204,
+
+	/*
+	 * Bit 1:0 controls LPSS controller reset.
+	 *
+	 * 00 ->LPSS Host Controller is in reset (Reset Asserted)
+	 * 01/10 ->Reserved
+	 * 11 ->LPSS Host Controller is NOT at reset (Reset Released)
+	 */
+	LPSS_CNT_RST_RELEASE	= 3,
+
+	/* Power management control and status register */
+	PME_CTRL_STATUS		= 0x84,
+
+	/* Bit 1:0 Powerstate, controls D0 and D3 state */
+	POWER_STATE_MASK	= 3,
+};
+
+/* Take controller out of reset */
+void lpss_reset_release(void *regs)
+{
+	writel(LPSS_CNT_RST_RELEASE, regs + LPSS_RESET_CTL_REG);
+}
+
+void lpss_set_power_state(struct udevice *dev, enum lpss_pwr_state state)
+{
+	dm_pci_clrset_config8(dev, PME_CTRL_STATUS, POWER_STATE_MASK, state);
+}

arch/x86/include/asm/lpss.h

@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef __ASM_LPSS_H
+#define __ASM_LPSS_H
+
+struct udevice;
+
+/* D0 and D3 enable config */
+enum lpss_pwr_state {
+	STATE_D0 = 0,
+	STATE_D3 = 3
+};
+
+/**
+ * lpss_reset_release() - Release device from reset
+ *
+ * This is used for devices which have LPSS support.
+ *
+ * @regs: Pointer to device registers
+ */
+void lpss_reset_release(void *regs);
+
+/**
+ * lpss_set_power_state() - Change power state of a device
+ *
+ * This is used for devices which have LPSS support.
+ *
+ * @dev: Device to update
+ * @state: New power state to set
+ */
+void lpss_set_power_state(struct udevice *dev, enum lpss_pwr_state state);
+
+#endif