linux-kernel - Re: [PATCH v3] power: reset: use restart

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Date:	Wed, 24 Sep 2014 07:38:05 +0530
From:	Pramod Gurav <pramod.gurav@...rtplayin.com>
To:	Kumar Gala <galak@...eaurora.org>
CC:	linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
	Josh Cartwright <joshc@...eaurora.org>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-pm@...r.kernel.org,
	linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v3] power: reset: use restart_notifier mechanism for msm-poweroff

Hi Kumar,

On 23-09-2014 11:18 PM, Kumar Gala wrote:
> 
> On Sep 23, 2014, at 1:28 AM, Pramod Gurav <pramod.gurav@...rtplayin.com> wrote:
> 
>> +linux-arm-msm
>> On Tuesday 23 September 2014 11:38 AM, Pramod Gurav wrote:
>>> This change replaces use of arm_pm_restart with recently introduced
>>> reset mechanism in Linux kernel called restart_notifier.
> 
> Can you update the commit message to include details about the priority level we are setting it to.
> 
> Probably something like Josh had:
> 
> Choose priority 128, as according to documentation, this mechanism "is
> sufficient to restart the entire system”.
Will update the commit message.
> 
> Hmm, what happens if we have ps_hold restart and msm-poweroff enabled.  Which one should have priority?
In case of A-family/apq8064, the ps_hold register region is owned by
pinctrl hence the reset is implemented in pinctrl driver as the region
is already mapped there.
I have had a discussion with Stephen Boyd and was informed that ps_hold
register region in apq8074/B-family are moved to its own region and we
need to reset it through pinctrl.

So, for b family there is no need for ps_hold to be configured/muxed in
pinctrl and Josh's changes wont execute. Hence msm-poweroff wil be the
default reset as 128 in the default priority.

Hope I was able to put it well to answer your comment.
> 
>>>
>>> Reviewed-by: Guenter Roeck <linux@...ck-us.net>
>>> Cc: Guenter Roeck <linux@...ck-us.net>
>>> Cc: Josh Cartwright <joshc@...eaurora.org>
>>> Cc: Sebastian Reichel <sre@...nel.org>
>>> Cc: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
>>> Cc: David Woodhouse <dwmw2@...radead.org>
>>> Cc: Stephen Boyd <sboyd@...eaurora.org>
>>> Cc: linux-pm@...r.kernel.org
>>>
>>> Signed-off-by: Pramod Gurav <pramod.gurav@...rtplayin.com>
>>> ---
>>> Tested on Dragonboard APQ8074
>>>
>>> Changes since v2:
>>> - Removed unwanted header file and added linux/pm.h
>>>
>>> Changes since v1:
>>> - Initialized restart_nb with its declaration
>>> - Removed return check for register_restart_handler as it always
>>>  returns 0 as per Guenter's suggestion to Josh's similar patch.
>>>  This takes care of Guenter's comments on error logs and NULL
>>>  initialization of restart_nb.notifier_call.
>>> ---
>>> drivers/power/reset/msm-poweroff.c |   20 ++++++++++++++------
>>> 1 file changed, 14 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/power/reset/msm-poweroff.c b/drivers/power/reset/msm-poweroff.c
>>> index 774f9a3..4702efd 100644
>>> --- a/drivers/power/reset/msm-poweroff.c
>>> +++ b/drivers/power/reset/msm-poweroff.c
>>> @@ -20,21 +20,27 @@
>>> #include <linux/platform_device.h>
>>> #include <linux/module.h>
>>> #include <linux/reboot.h>
>>> -
>>> -#include <asm/system_misc.h>
>>> +#include <linux/pm.h>
>>>
>>> static void __iomem *msm_ps_hold;
>>> -
>>> -static void do_msm_restart(enum reboot_mode reboot_mode, const char *cmd)
>>> +static int do_msm_restart(struct notifier_block *nb, unsigned long action,
>>> +			   void *data)
>>> {
>>> 	writel(0, msm_ps_hold);
>>> 	mdelay(10000);
>>> +
>>> +	return NOTIFY_DONE;
>>> }
>>>
>>> +static struct notifier_block restart_nb = {
>>> +	.notifier_call = do_msm_restart,
>>> +	.priority = 128,
>>> +};
>>> +
>>> static void do_msm_poweroff(void)
>>> {
>>> 	/* TODO: Add poweroff capability */
>>> -	do_msm_restart(REBOOT_HARD, NULL);
>>> +	do_msm_restart(&restart_nb, 0, NULL);
>>> }
>>>
>>> static int msm_restart_probe(struct platform_device *pdev)
>>> @@ -47,8 +53,10 @@ static int msm_restart_probe(struct platform_device *pdev)
>>> 	if (IS_ERR(msm_ps_hold))
>>> 		return PTR_ERR(msm_ps_hold);
>>>
>>> +	register_restart_handler(&restart_nb);
>>> +
>>> 	pm_power_off = do_msm_poweroff;
>>> -	arm_pm_restart = do_msm_restart;
>>> +
>>> 	return 0;
>>> }
>>>
>>>
>> --
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> 
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