soc: ti: Add pm33xx driver for basic suspend support

AM335x and AM437x support various low power modes as documented
in section 8.1.4.3 of the AM335x Technical Reference Manual and
section 6.4.3 of the AM437x Technical Reference Manual.

DeepSleep0 mode offers the lowest power mode with limited
wakeup sources without a system reboot and is mapped as
the suspend state in the kernel. In this state, MPU and
PER domains are turned off with the internal RAM held in
retention to facilitate the resume process. As part of
the boot process, the assembly code is copied over to OCMCRAM
so it can be executed to turn of the EMIF and put DDR into self
refresh.

Both platforms have a Cortex-M3 (WKUP_M3) which assists the MPU
in DeepSleep0 entry and exit. WKUP_M3 takes care
of the clockdomain and powerdomain transitions based on the
intended low power state. MPU needs to load the appropriate
WKUP_M3 binary onto the WKUP_M3 memory space before it can
leverage any of the PM features like DeepSleep. This loading
is handled by the remoteproc driver wkup_m3_rproc.

Communication with the WKUP_M3 is handled by a wkup_m3_ipc
driver that exposes the specific PM functionality to be used
the PM code.

In the current implementation when the suspend process
is initiated, MPU interrupts the WKUP_M3 to let it know about
the intent of entering DeepSleep0 and waits for an ACK. When
the ACK is received MPU continues with its suspend process
to suspend all the drivers and then jumps to assembly in
OCMC RAM. The assembly code puts the external RAM in self-refresh
mode, gates the MPU clock, and then finally executes the WFI
instruction. Execution of the WFI instruction with MPU clock gated
triggers another interrupt to the WKUP_M3 which then continues
with the power down sequence wherein the clockdomain and
powerdomain transition takes place. As part of the sleep sequence,
WKUP_M3 unmasks the interrupt lines for the wakeup sources. WFI
execution on WKUP_M3 causes the hardware to disable the main
oscillator of the SoC and from here system remains in sleep state
until a wake source brings the system into resume path.

When a wakeup event occurs, WKUP_M3 starts the power-up
sequence by switching on the power domains and finally
enabling the clock to MPU. Since the MPU gets powered down
as part of the sleep sequence in the resume path ROM code
starts executing. The ROM code detects a wakeup from sleep
and then jumps to the resume location in OCMC which was
populated in one of the IPC registers as part of the suspend
sequence.

Code is based on work by Vaibhav Bedia.

Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/arm/omap/mpu.txt

@@ -13,6 +13,13 @@ Required properties:
 Optional properties:
 - sram:	Phandle to the ocmcram node
 
+am335x and am437x only:
+- pm-sram: Phandles to ocmcram nodes to be used for power management.
+	   First should be type 'protect-exec' for the driver to use to copy
+	   and run PM functions, second should be regular pool to be used for
+	   data region for code. See Documentation/devicetree/bindings/sram/sram.txt
+	   for more details.
+
 Examples:
 
 - For an OMAP5 SMP system:
@@ -36,3 +43,12 @@ mpu {
     compatible = "ti,omap3-mpu";
     ti,hwmods = "mpu";
 };
+
+- For an AM335x system:
+
+mpu {
+	compatible = "ti,omap3-mpu";
+	ti,hwmods = "mpu";
+	pm-sram = <&pm_sram_code
+		   &pm_sram_data>;
+};

drivers/soc/ti/Kconfig

@@ -28,6 +28,15 @@ config KEYSTONE_NAVIGATOR_DMA
 
 	  If unsure, say N.
 
+config AMX3_PM
+	tristate "AMx3 Power Management"
+	depends on SOC_AM33XX || SOC_AM43XX
+	depends on WKUP_M3_IPC && TI_EMIF_SRAM && SRAM
+	help
+	  Enable power management on AM335x and AM437x. Required for suspend to mem
+	  and standby states on both AM335x and AM437x platforms and for deeper cpuidle
+	  c-states on AM335x.
+
 config WKUP_M3_IPC
 	tristate "TI AMx3 Wkup-M3 IPC Driver"
 	depends on WKUP_M3_RPROC

drivers/soc/ti/Makefile

@@ -5,5 +5,6 @@
 obj-$(CONFIG_KEYSTONE_NAVIGATOR_QMSS)	+= knav_qmss.o
 knav_qmss-y := knav_qmss_queue.o knav_qmss_acc.o
 obj-$(CONFIG_KEYSTONE_NAVIGATOR_DMA)	+= knav_dma.o
+obj-$(CONFIG_AMX3_PM)			+= pm33xx.o
 obj-$(CONFIG_WKUP_M3_IPC)		+= wkup_m3_ipc.o
 obj-$(CONFIG_TI_SCI_PM_DOMAINS)		+= ti_sci_pm_domains.o

drivers/soc/ti/pm33xx.c

@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * AM33XX Power Management Routines
+ *
+ * Copyright (C) 2012-2018 Texas Instruments Incorporated - http://www.ti.com/
+ *	Vaibhav Bedia, Dave Gerlach
+ */
+
+#include <linux/cpu.h>
+#include <linux/err.h>
+#include <linux/genalloc.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_data/pm33xx.h>
+#include <linux/platform_device.h>
+#include <linux/sizes.h>
+#include <linux/sram.h>
+#include <linux/suspend.h>
+#include <linux/ti-emif-sram.h>
+#include <linux/wkup_m3_ipc.h>
+
+#include <asm/proc-fns.h>
+#include <asm/suspend.h>
+#include <asm/system_misc.h>
+
+#define AMX3_PM_SRAM_SYMBOL_OFFSET(sym) ((unsigned long)(sym) - \
+					 (unsigned long)pm_sram->do_wfi)
+
+static int (*am33xx_do_wfi_sram)(unsigned long unused);
+static phys_addr_t am33xx_do_wfi_sram_phys;
+
+static struct gen_pool *sram_pool, *sram_pool_data;
+static unsigned long ocmcram_location, ocmcram_location_data;
+
+static struct am33xx_pm_platform_data *pm_ops;
+static struct am33xx_pm_sram_addr *pm_sram;
+
+static struct device *pm33xx_dev;
+static struct wkup_m3_ipc *m3_ipc;
+
+static u32 sram_suspend_address(unsigned long addr)
+{
+	return ((unsigned long)am33xx_do_wfi_sram +
+		AMX3_PM_SRAM_SYMBOL_OFFSET(addr));
+}
+
+#ifdef CONFIG_SUSPEND
+static int am33xx_pm_suspend(suspend_state_t suspend_state)
+{
+	int i, ret = 0;
+
+	ret = pm_ops->soc_suspend((unsigned long)suspend_state,
+				  am33xx_do_wfi_sram);
+
+	if (ret) {
+		dev_err(pm33xx_dev, "PM: Kernel suspend failure\n");
+	} else {
+		i = m3_ipc->ops->request_pm_status(m3_ipc);
+
+		switch (i) {
+		case 0:
+			dev_info(pm33xx_dev,
+				 "PM: Successfully put all powerdomains to target state\n");
+			break;
+		case 1:
+			dev_err(pm33xx_dev,
+				"PM: Could not transition all powerdomains to target state\n");
+			ret = -1;
+			break;
+		default:
+			dev_err(pm33xx_dev,
+				"PM: CM3 returned unknown result = %d\n", i);
+			ret = -1;
+		}
+	}
+
+	return ret;
+}
+
+static int am33xx_pm_enter(suspend_state_t suspend_state)
+{
+	int ret = 0;
+
+	switch (suspend_state) {
+	case PM_SUSPEND_MEM:
+	case PM_SUSPEND_STANDBY:
+		ret = am33xx_pm_suspend(suspend_state);
+		break;
+	default:
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static int am33xx_pm_begin(suspend_state_t state)
+{
+	int ret = -EINVAL;
+
+	switch (state) {
+	case PM_SUSPEND_MEM:
+		ret = m3_ipc->ops->prepare_low_power(m3_ipc, WKUP_M3_DEEPSLEEP);
+		break;
+	case PM_SUSPEND_STANDBY:
+		ret = m3_ipc->ops->prepare_low_power(m3_ipc, WKUP_M3_STANDBY);
+		break;
+	}
+
+	return ret;
+}
+
+static void am33xx_pm_end(void)
+{
+	m3_ipc->ops->finish_low_power(m3_ipc);
+}
+
+static int am33xx_pm_valid(suspend_state_t state)
+{
+	switch (state) {
+	case PM_SUSPEND_STANDBY:
+	case PM_SUSPEND_MEM:
+		return 1;
+	default:
+		return 0;
+	}
+}
+
+static const struct platform_suspend_ops am33xx_pm_ops = {
+	.begin		= am33xx_pm_begin,
+	.end		= am33xx_pm_end,
+	.enter		= am33xx_pm_enter,
+	.valid		= am33xx_pm_valid,
+};
+#endif /* CONFIG_SUSPEND */
+
+static void am33xx_pm_set_ipc_ops(void)
+{
+	u32 resume_address;
+	int temp;
+
+	temp = ti_emif_get_mem_type();
+	if (temp < 0) {
+		dev_err(pm33xx_dev, "PM: Cannot determine memory type, no PM available\n");
+		return;
+	}
+	m3_ipc->ops->set_mem_type(m3_ipc, temp);
+
+	/* Physical resume address to be used by ROM code */
+	resume_address = am33xx_do_wfi_sram_phys +
+			 *pm_sram->resume_offset + 0x4;
+
+	m3_ipc->ops->set_resume_address(m3_ipc, (void *)resume_address);
+}
+
+static void am33xx_pm_free_sram(void)
+{
+	gen_pool_free(sram_pool, ocmcram_location, *pm_sram->do_wfi_sz);
+	gen_pool_free(sram_pool_data, ocmcram_location_data,
+		      sizeof(struct am33xx_pm_ro_sram_data));
+}
+
+/*
+ * Push the minimal suspend-resume code to SRAM
+ */
+static int am33xx_pm_alloc_sram(void)
+{
+	struct device_node *np;
+	int ret = 0;
+
+	np = of_find_compatible_node(NULL, NULL, "ti,omap3-mpu");
+	if (!np) {
+		np = of_find_compatible_node(NULL, NULL, "ti,omap4-mpu");
+		if (!np) {
+			dev_err(pm33xx_dev, "PM: %s: Unable to find device node for mpu\n",
+				__func__);
+			return -ENODEV;
+		}
+	}
+
+	sram_pool = of_gen_pool_get(np, "pm-sram", 0);
+	if (!sram_pool) {
+		dev_err(pm33xx_dev, "PM: %s: Unable to get sram pool for ocmcram\n",
+			__func__);
+		ret = -ENODEV;
+		goto mpu_put_node;
+	}
+
+	sram_pool_data = of_gen_pool_get(np, "pm-sram", 1);
+	if (!sram_pool_data) {
+		dev_err(pm33xx_dev, "PM: %s: Unable to get sram data pool for ocmcram\n",
+			__func__);
+		ret = -ENODEV;
+		goto mpu_put_node;
+	}
+
+	ocmcram_location = gen_pool_alloc(sram_pool, *pm_sram->do_wfi_sz);
+	if (!ocmcram_location) {
+		dev_err(pm33xx_dev, "PM: %s: Unable to allocate memory from ocmcram\n",
+			__func__);
+		ret = -ENOMEM;
+		goto mpu_put_node;
+	}
+
+	ocmcram_location_data = gen_pool_alloc(sram_pool_data,
+					       sizeof(struct emif_regs_amx3));
+	if (!ocmcram_location_data) {
+		dev_err(pm33xx_dev, "PM: Unable to allocate memory from ocmcram\n");
+		gen_pool_free(sram_pool, ocmcram_location, *pm_sram->do_wfi_sz);
+		ret = -ENOMEM;
+	}
+
+mpu_put_node:
+	of_node_put(np);
+	return ret;
+}
+
+static int am33xx_push_sram_idle(void)
+{
+	struct am33xx_pm_ro_sram_data ro_sram_data;
+	int ret;
+	u32 table_addr, ro_data_addr;
+	void *copy_addr;
+
+	ro_sram_data.amx3_pm_sram_data_virt = ocmcram_location_data;
+	ro_sram_data.amx3_pm_sram_data_phys =
+		gen_pool_virt_to_phys(sram_pool_data, ocmcram_location_data);
+
+	/* Save physical address to calculate resume offset during pm init */
+	am33xx_do_wfi_sram_phys = gen_pool_virt_to_phys(sram_pool,
+							ocmcram_location);
+
+	am33xx_do_wfi_sram = sram_exec_copy(sram_pool, (void *)ocmcram_location,
+					    pm_sram->do_wfi,
+					    *pm_sram->do_wfi_sz);
+	if (!am33xx_do_wfi_sram) {
+		dev_err(pm33xx_dev,
+			"PM: %s: am33xx_do_wfi copy to sram failed\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	table_addr =
+		sram_suspend_address((unsigned long)pm_sram->emif_sram_table);
+	ret = ti_emif_copy_pm_function_table(sram_pool, (void *)table_addr);
+	if (ret) {
+		dev_dbg(pm33xx_dev,
+			"PM: %s: EMIF function copy failed\n", __func__);
+		return -EPROBE_DEFER;
+	}
+
+	ro_data_addr =
+		sram_suspend_address((unsigned long)pm_sram->ro_sram_data);
+	copy_addr = sram_exec_copy(sram_pool, (void *)ro_data_addr,
+				   &ro_sram_data,
+				   sizeof(ro_sram_data));
+	if (!copy_addr) {
+		dev_err(pm33xx_dev,
+			"PM: %s: ro_sram_data copy to sram failed\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int am33xx_pm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	if (!of_machine_is_compatible("ti,am33xx") &&
+	    !of_machine_is_compatible("ti,am43"))
+		return -ENODEV;
+
+	pm_ops = dev->platform_data;
+	if (!pm_ops) {
+		dev_err(dev, "PM: Cannot get core PM ops!\n");
+		return -ENODEV;
+	}
+
+	pm_sram = pm_ops->get_sram_addrs();
+	if (!pm_sram) {
+		dev_err(dev, "PM: Cannot get PM asm function addresses!!\n");
+		return -ENODEV;
+	}
+
+	pm33xx_dev = dev;
+
+	ret = am33xx_pm_alloc_sram();
+	if (ret)
+		return ret;
+
+	ret = am33xx_push_sram_idle();
+	if (ret)
+		goto err_free_sram;
+
+	m3_ipc = wkup_m3_ipc_get();
+	if (!m3_ipc) {
+		dev_dbg(dev, "PM: Cannot get wkup_m3_ipc handle\n");
+		ret = -EPROBE_DEFER;
+		goto err_free_sram;
+	}
+
+	am33xx_pm_set_ipc_ops();
+
+#ifdef CONFIG_SUSPEND
+	suspend_set_ops(&am33xx_pm_ops);
+#endif /* CONFIG_SUSPEND */
+
+	ret = pm_ops->init();
+	if (ret) {
+		dev_err(dev, "Unable to call core pm init!\n");
+		ret = -ENODEV;
+		goto err_put_wkup_m3_ipc;
+	}
+
+	return 0;
+
+err_put_wkup_m3_ipc:
+	wkup_m3_ipc_put(m3_ipc);
+err_free_sram:
+	am33xx_pm_free_sram();
+	pm33xx_dev = NULL;
+	return ret;
+}
+
+static int am33xx_pm_remove(struct platform_device *pdev)
+{
+	suspend_set_ops(NULL);
+	wkup_m3_ipc_put(m3_ipc);
+	am33xx_pm_free_sram();
+	return 0;
+}
+
+static struct platform_driver am33xx_pm_driver = {
+	.driver = {
+		.name   = "pm33xx",
+	},
+	.probe = am33xx_pm_probe,
+	.remove = am33xx_pm_remove,
+};
+module_platform_driver(am33xx_pm_driver);
+
+MODULE_ALIAS("platform:pm33xx");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("am33xx power management driver");