Subject: [RFC v2 16/18] ARM: OMAP2+: AM33XX: Basic suspend resume support

From: [email-masked] (Kevin Hilman)
Date: Mon, 11 Feb 2013 17:27:50 -0800

Hi Viabhav,

Vaibhav Bedia <[email-masked]> writes:

> AM335x supports various low power modes as documented
> in section 8.1.4.3 of the AM335x TRM which is available
> @ http://www.ti.com/litv/pdf/spruh73f
>
> 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 resume process. As part of the boot
> process, the assembly code is copied over to OCMCRAM using
> the OMAP SRAM code.
>
> AM335x has 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.
>
> The IPC mechanism between MPU and WKUP_M3 uses a mailbox
> sub-module and 8 IPC registers in the Control module. MPU
> uses the assigned Mailbox for issuing an interrupt to
> WKUP_M3 which then goes and checks the IPC registers for
> the payload. WKUP_M3 has the ability to trigger on interrupt
> to MPU by executing the "sev" instruction.
>
> 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 PLLs in bypass, puts the
> external RAM in self-refresh mode and then finally execute the
> WFI instruction. Execution of the WFI instruction triggers another
> interrupt to the WKUP_M3 which then continues wiht 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.
>
> 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.
>
> The low level code in OCMC relocks the PLLs, enables access
> to external RAM and then jumps to the cpu_resume code of
> the kernel to finish the resume process.
>
> Signed-off-by: Vaibhav Bedia <[email-masked]>
> Cc: Tony Lingren <[email-masked]>
> Cc: Santosh Shilimkar <[email-masked]>
> Cc: Benoit Cousson <[email-masked]>
> Cc: Paul Walmsley <[email-masked]>
> Cc: Kevin Hilman <[email-masked]>

Thanks for the updated series here, and my apologies for the delayed
review.

I've just had a quick scan of this patch, and have a few general
comments, I'll probably have a few more comments after a closer look.

> ---
> v1->v2:
> 	Move assembly code addition, control module access
> 	and hookup in OMAP PM framework in separate patches.
> 	Address other comments from Kevin Hilman and Santosh
> 	Shilimkar on v1. The discussion on v1 is present @
> 	http://lists.infradead.org/pipermail/linux-arm-kernel/2012-November/129979.html
> 	Note: The mailbox change will need slight rework once
> 	the driver is finalized.
>
>  arch/arm/mach-omap2/pm33xx.c |  469 ++++++++++++++++++++++++++++++++++++++++++
>  arch/arm/mach-omap2/pm33xx.h |   56 +++++
>  2 files changed, 525 insertions(+), 0 deletions(-)
>  create mode 100644 arch/arm/mach-omap2/pm33xx.c
>  create mode 100644 arch/arm/mach-omap2/pm33xx.h
>
> diff --git a/arch/arm/mach-omap2/pm33xx.c b/arch/arm/mach-omap2/pm33xx.c
> new file mode 100644
> index 0000000..aaa4daa
> --- /dev/null
> +++ b/arch/arm/mach-omap2/pm33xx.c
> @@ -0,0 +1,469 @@
> +/*
> + * AM33XX Power Management Routines
> + *
> + * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
> + * Vaibhav Bedia <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation version 2.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/err.h>
> +#include <linux/firmware.h>
> +#include <linux/io.h>
> +#include <linux/platform_device.h>
> +#include <linux/sched.h>
> +#include <linux/suspend.h>
> +#include <linux/completion.h>
> +#include <linux/module.h>
> +#include <linux/mailbox.h>
> +#include <linux/interrupt.h>
> +
> +#include <asm/suspend.h>
> +#include <asm/proc-fns.h>
> +#include <asm/sizes.h>
> +#include <asm/fncpy.h>
> +#include <asm/system_misc.h>
> +
> +#include "pm.h"
> +#include "cm33xx.h"
> +#include "pm33xx.h"
> +#include "control.h"
> +#include "clockdomain.h"
> +#include "powerdomain.h"
> +#include "omap_hwmod.h"
> +#include "omap_device.h"
> +#include "soc.h"
> +#include "sram.h"
> +
> +void (*am33xx_do_wfi_sram)(void);

static?

> +static void __iomem *am33xx_emif_base;
> +static struct powerdomain *cefuse_pwrdm, *gfx_pwrdm, *per_pwrdm;
> +static struct clockdomain *gfx_l4ls_clkdm;
> +static struct omap_hwmod *usb_oh, *cpsw_oh, *tptc0_oh, *tptc1_oh, *tptc2_oh;
> +static struct wkup_m3_context *wkup_m3;
> +
> +static DECLARE_COMPLETION(wkup_m3_sync);
> +
> +#ifdef CONFIG_SUSPEND
> +static int am33xx_do_sram_idle(long unsigned int unused)
> +{
> +	am33xx_do_wfi_sram();
> +	return 0;
> +}
> +
> +static int am33xx_pm_suspend(void)
> +{
> +	int status, ret = 0;
> +
> +	/*
> +	 * By default the following IPs do not have MSTANDBY asserted
> +	 * which is necessary for PER domain transition. If the drivers
> +	 * are not compiled into the kernel HWMOD code will not change the
> +	 * state of the IPs if the IP was not never enabled. To ensure
> +	 * that there no issues with or without the drivers being compiled
> +	 * in the kernel, we forcefully put these IPs to idle.
> +	 */
> +	omap_hwmod_enable(usb_oh);
> +	omap_hwmod_enable(tptc0_oh);
> +	omap_hwmod_enable(tptc1_oh);
> +	omap_hwmod_enable(tptc2_oh);
> +	omap_hwmod_enable(cpsw_oh);
> +
> +	omap_hwmod_idle(usb_oh);
> +	omap_hwmod_idle(tptc0_oh);
> +	omap_hwmod_idle(tptc1_oh);
> +	omap_hwmod_idle(tptc2_oh);
> +	omap_hwmod_idle(cpsw_oh);

I think I asked this in my review of v1, but why does this need to
happen on every suspend attempt?

This should happen once on init, which will handle the case where there
are no drivers, and if there are drivers, then the drivers need to
handle this properly.  

I don't like this happening here on every suspend attempt, because it
will surely hide bugs where drivers are not properly managing their own PM.

> +	/* Try to put GFX to sleep */
> +	pwrdm_set_next_fpwrst(gfx_pwrdm, PWRDM_FUNC_PWRST_OFF);
> +
> +	ret = cpu_suspend(0, am33xx_do_sram_idle);
> +	status = pwrdm_read_fpwrst(gfx_pwrdm);
> +	if (status != PWRDM_FUNC_PWRST_OFF)
> +		pr_err("GFX domain did not transition\n");
> +	else
> +		pr_info("GFX domain entered low power state\n");

Do you really want this printed every time?

> +	/*
> +	 * GFX_L4LS clock domain needs to be woken up to
> +	 * ensure thet L4LS clock domain does not get stuck in transition
> +	 * If that happens L3 module does not get disabled, thereby leading
> +	 * to PER power domain transition failing
> +	 *
> +	 * The clock framework should take care of ensuring
> +	 * that the clock domain is in the right state when
> +	 * GFX driver is active.

Are you suggesting that the clock framework is not doing this already?

> +	 */
> +	clkdm_wakeup(gfx_l4ls_clkdm);
> +	clkdm_sleep(gfx_l4ls_clkdm);
> +
> +	if (ret) {
> +		pr_err("Kernel suspend failure\n");
> +	} else {
> +		status = omap_ctrl_readl(AM33XX_CONTROL_IPC_MSG_REG1);

We're trying to git rid of direct control module register access, and
consolidate them into control.c (for an eventual move to a driver.)  I
see you've mostly done that in other parts of the series, but here's one
that needs to move.

> +		status &= IPC_RESP_MASK;
> +		status >>= __ffs(IPC_RESP_MASK);
> +
> +		switch (status) {
> +		case 0:
> +			pr_info("Successfully put all powerdomains to target state\n");
> +			/*
> +			 * XXX: Leads to loss of logic state in PER power domain
> +			 * Use SOC specific ops for this?
> +			 */

huh?

> +			break;
> +		case 1:
> +			pr_err("Could not transition all powerdomains to target state\n");
> +			ret = -1;
> +			break;
> +		default:
> +			pr_err("Something went wrong :(\nStatus = %d\n",
> +				status);
> +			ret = -1;
> +		}
> +	}
> +
> +	return ret;
> +}
> +
> +static int am33xx_pm_enter(suspend_state_t suspend_state)
> +{
> +	int ret = 0;
> +
> +	switch (suspend_state) {
> +	case PM_SUSPEND_STANDBY:
> +	case PM_SUSPEND_MEM:
> +		ret = am33xx_pm_suspend();
> +		break;
> +	default:
> +		ret = -EINVAL;
> +	}
> +
> +	return ret;
> +}
> +
> +static int am33xx_pm_begin(suspend_state_t state)
> +{
> +	int ret = 0;
> +	struct mailbox_msg dummy_msg;
> +
> +	disable_hlt();
> +
> +	MAILBOX_FILL_HEADER_MSG(dummy_msg, 0xABCDABCD);
> +
> +	wkup_m3->ipc_data.sleep_mode = IPC_CMD_DS0;
> +	wkup_m3->ipc_data.param1  = DS_IPC_DEFAULT;
> +	wkup_m3->ipc_data.param2  = DS_IPC_DEFAULT;
> +
> +	am33xx_wkup_m3_ipc_cmd(&wkup_m3->ipc_data);
> +
> +	wkup_m3->state = M3_STATE_MSG_FOR_LP;
> +
> +	mailbox_enable_irq(wkup_m3->mbox, IRQ_RX);
> +
> +	ret = mailbox_msg_send(wkup_m3->mbox, &dummy_msg);
> +	if (ret) {
> +		pr_err("A8<->CM3 MSG for LP failed\n");
> +		am33xx_m3_state_machine_reset();
> +		ret = -1;
> +	}
> +
> +	/* Give some time to M3 to respond. 500msec is a random value here */

random?  really?

> +	if (!wait_for_completion_timeout(&wkup_m3_sync,
> +					msecs_to_jiffies(500))) {
> +		pr_err("A8<->CM3 sync failure\n");
> +		am33xx_m3_state_machine_reset();
> +		ret = -1;
> +	} else {
> +		pr_debug("Message sent for entering DeepSleep mode\n");
> +		mailbox_disable_irq(wkup_m3->mbox, IRQ_RX);
> +	}
> +
> +	return ret;
> +}
> +
> +static void am33xx_pm_end(void)
> +{
> +	mailbox_enable_irq(wkup_m3->mbox, IRQ_RX);
> +
> +	am33xx_m3_state_machine_reset();
> +
> +	enable_hlt();
> +
> +	return;
> +}
> +
> +static const struct platform_suspend_ops am33xx_pm_ops = {
> +	.begin		= am33xx_pm_begin,
> +	.end		= am33xx_pm_end,
> +	.enter		= am33xx_pm_enter,
> +	.valid		= suspend_valid_only_mem,
> +};
> +
> +static void am33xx_m3_state_machine_reset(void)
> +{
> +	int ret = 0;
> +	struct mailbox_msg dummy_msg;
> +
> +	MAILBOX_FILL_HEADER_MSG(dummy_msg, 0xABCDABCD);
> +
> +	wkup_m3->ipc_data.sleep_mode	= IPC_CMD_RESET;
> +	wkup_m3->ipc_data.param1	= DS_IPC_DEFAULT;
> +	wkup_m3->ipc_data.param2	= DS_IPC_DEFAULT;
> +
> +	am33xx_wkup_m3_ipc_cmd(&wkup_m3->ipc_data);
> +
> +	wkup_m3->state = M3_STATE_MSG_FOR_RESET;
> +
> +	ret = mailbox_msg_send(wkup_m3->mbox, &dummy_msg);
> +	if (!ret) {
> +		pr_debug("Message sent for resetting M3 state machine\n");
> +		/* Give some to M3 to respond. 500msec is a random value here */
> +		if (!wait_for_completion_timeout(&wkup_m3_sync,
> +						msecs_to_jiffies(500)))
> +			pr_err("A8<->CM3 sync failure\n");
> +	} else {
> +		pr_err("Could not reset M3 state machine!!!\n");
> +		wkup_m3->state = M3_STATE_UNKNOWN;
> +	}
> +}
> +#endif /* CONFIG_SUSPEND */
> +
> +/*
> + * Dummy notifier for the mailbox
> + * XXX: Get rid of this requirement once the MBX driver has been finalized

IIRC, I suggested a trivial fix to the mailbox driver that would remove
the need for this, which could be done today.

> + */
> +static int wkup_mbox_msg(struct notifier_block *self, unsigned long len,
> +		void *msg)
> +{
> +	return 0;
> +}
> +
> +static struct notifier_block wkup_mbox_notifier = {
> +	.notifier_call = wkup_mbox_msg,
> +};
> +
> +static irqreturn_t wkup_m3_txev_handler(int irq, void *unused)
> +{
> +	am33xx_txev_eoi();
> +
> +	switch (wkup_m3->state) {
> +	case M3_STATE_RESET:
> +		wkup_m3->state = M3_STATE_INITED;
> +		break;
> +	case M3_STATE_MSG_FOR_RESET:
> +		wkup_m3->state = M3_STATE_INITED;
> +		mailbox_rx_flush(wkup_m3->mbox);
> +		complete(&wkup_m3_sync);
> +		break;
> +	case M3_STATE_MSG_FOR_LP:
> +		mailbox_rx_flush(wkup_m3->mbox);
> +		complete(&wkup_m3_sync);
> +		break;
> +	case M3_STATE_UNKNOWN:
> +		pr_err("IRQ %d with WKUP_M3 in unknown state\n", irq);
> +		mailbox_rx_flush(wkup_m3->mbox);
> +		return IRQ_NONE;
> +	}
> +
> +	am33xx_txev_enable();
> +	return IRQ_HANDLED;
> +}
> +
> +static void am33xx_pm_firmware_cb(const struct firmware *fw, void *context)
> +{
> +	struct wkup_m3_context *wkup_m3_context = context;
> +	struct platform_device *pdev = to_platform_device(wkup_m3_context->dev);
> +	int ret = 0;
> +
> +	/* no firmware found */
> +	if (!fw) {
> +		dev_err(wkup_m3_context->dev, "request_firmware failed\n");
> +		goto err;
> +	}
> +
> +	memcpy((void *)wkup_m3_context->code, fw->data, fw->size);
> +	pr_info("Copied the M3 firmware to UMEM\n");
> +
> +	wkup_m3->state = M3_STATE_RESET;
> +
> +	ret = omap_device_deassert_hardreset(pdev, "wkup_m3");
> +	if (ret) {
> +		pr_err("Could not deassert the reset for WKUP_M3\n");
> +		goto err;
> +	} else {
> +#ifdef CONFIG_SUSPEND
> +		suspend_set_ops(&am33xx_pm_ops);
> +		/*
> +		 * Physical resume address to be used by ROM code
> +		 */
> +		wkup_m3->ipc_data.resume_addr = (AM33XX_OCMC_END -
> +				am33xx_do_wfi_sz + am33xx_resume_offset + 0x4);
> +#endif
> +		return;
> +	}
> +
> +err:
> +	mailbox_put(wkup_m3_context->mbox, &wkup_mbox_notifier);
> +}
> +
> +static int wkup_m3_init(void)
> +{
> +	int irq, ret = 0;
> +	struct resource *mem;
> +	struct platform_device *pdev = to_platform_device(wkup_m3->dev);
> +
> +	omap_device_enable_hwmods(to_omap_device(pdev));

Why not omap_device_enable(pdev) ?

> +
> +	/* Reserve the MBOX for sending messages to M3 */
> +	wkup_m3->mbox = mailbox_get("wkup_m3", &wkup_mbox_notifier);
> +	if (IS_ERR(wkup_m3->mbox)) {
> +		pr_err("Could not reserve mailbox for A8->M3 IPC\n");
> +		ret = -ENODEV;
> +		goto exit;
> +	}
> +
> +	irq = platform_get_irq(pdev, 0);
> +	if (!irq) {
> +		dev_err(wkup_m3->dev, "no irq resource\n");
> +		ret = -ENXIO;
> +		goto err;
> +	}
> +
> +	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!mem) {
> +		dev_err(wkup_m3->dev, "no memory resource\n");
> +		ret = -ENXIO;
> +		goto err;
> +	}
> +
> +	wkup_m3->code = devm_request_and_ioremap(wkup_m3->dev, mem);
> +	if (!wkup_m3->code) {
> +		dev_err(wkup_m3->dev, "could not ioremap\n");
> +		ret = -EADDRNOTAVAIL;
> +		goto err;
> +	}
> +
> +	ret = devm_request_irq(wkup_m3->dev, irq, wkup_m3_txev_handler,
> +		  IRQF_DISABLED, "wkup_m3_txev", NULL);
> +	if (ret) {
> +		dev_err(wkup_m3->dev, "request_irq failed\n");
> +		goto err;
> +	} else {
> +		am33xx_txev_enable();
> +	}
> +
> +	pr_info("Trying to load am335x-pm-firmware.bin");
> +
> +	/* We don't want to delay boot */
> +	request_firmware_nowait(THIS_MODULE, 0, "am335x-pm-firmware.bin",
> +				wkup_m3->dev, GFP_KERNEL, wkup_m3,
> +				am33xx_pm_firmware_cb);
> +	return 0;
> +
> +err:
> +	mailbox_put(wkup_m3->mbox, &wkup_mbox_notifier);
> +exit:
> +	return ret;
> +}

Kevin