linux-kernel - RE: [PATCH v1] soc: fsl: rcpm: Add ACPI support

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Message-ID: <AM6PR04MB5413903EAAEDB2EED2E254C6F1210@AM6PR04MB5413.eurprd04.prod.outlook.com>
Date:   Wed, 16 Sep 2020 01:32:29 +0000
From:   Ran Wang <ran.wang_1@....com>
To:     Ard Biesheuvel <ard.biesheuvel@....com>,
        kuldip dwivedi <kuldip.dwivedi@...esoftware.com>,
        Leo Li <leoyang.li@....com>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Biwen Li <biwen.li@....com>, Varun Sethi <V.Sethi@....com>,
        Arokia Samy <arokia.samy@....com>,
        Samer El-Haj-Mahmoud <Samer.El-Haj-Mahmoud@....com>,
        Paul Yang <Paul.Yang@....com>,
        tanveer <tanveer.alam@...esoftware.com>
Subject: RE: [PATCH v1] soc: fsl: rcpm: Add ACPI support

Hi Ard,

On Tuesday, September 15, 2020 7:10 PM, Ard Biesheuvel wrote:
> Subject: Re: [PATCH v1] soc: fsl: rcpm: Add ACPI support
> 
> On 9/15/20 1:06 PM, kuldip dwivedi wrote:
> > Add ACPI support in fsl RCPM driver. This is required to support ACPI
> > S3 state. S3 is the ACPI sleep state that is known as "sleep" or
> > "suspend to RAM".
> > It essentially turns off most power of the system but keeps memory
> > powered.
> >
> > Signed-off-by: tanveer <tanveer.alam@...esoftware.com>
> > Signed-off-by: kuldip dwivedi <kuldip.dwivedi@...esoftware.com>
> 
> Why does the OS need to program this device? Can't this be done by
> firmware?

This device is use to tell HW which IP (such as USB, SDHC, SATA, etc) should not be
clock gated during system enter low power state (to allow that IP work as a
wakeup source). And user does this configuration in device tree. So implement
this RCPM driver to do it in kernel rather than firmware.

Regards,
Ran

> > ---
> >
> > Notes:
> >      1. Add ACPI match table
> >      2. NXP team members are added for confirming HID changes
> >      3. There is only one node in ACPI so no need to check for
> >         current device explicitly
> >      4. These changes are tested on LX2160A and LS1046A platforms
> >
> >   drivers/soc/fsl/rcpm.c | 22 +++++++++++++++++++---
> >   1 file changed, 19 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/soc/fsl/rcpm.c b/drivers/soc/fsl/rcpm.c index
> > a093dbe6d2cb..e75a436fb159 100644
> > --- a/drivers/soc/fsl/rcpm.c
> > +++ b/drivers/soc/fsl/rcpm.c
> > @@ -2,10 +2,12 @@
> >   //
> >   // rcpm.c - Freescale QorIQ RCPM driver
> >   //
> > -// Copyright 2019 NXP
> > +// Copyright 2019-2020 NXP
> > +// Copyright 2020 Puresoftware Ltd.
> >   //
> >   // Author: Ran Wang <ran.wang_1@....com>
> >
> > +#include <linux/acpi.h>
> >   #include <linux/init.h>
> >   #include <linux/module.h>
> >   #include <linux/platform_device.h>
> > @@ -57,8 +59,13 @@ static int rcpm_pm_prepare(struct device *dev)
> >   				rcpm->wakeup_cells + 1);
> >
> >   		/*  Wakeup source should refer to current rcpm device */
> > -		if (ret || (np->phandle != value[0]))
> > -			continue;
> > +		if (is_acpi_node(dev->fwnode)) {
> > +			if (ret)
> > +				continue;
> > +		} else {
> > +			if (ret || (np->phandle != value[0]))
> > +				continue;
> > +		}
> >
> >   		/* Property "#fsl,rcpm-wakeup-cells" of rcpm node defines the
> >   		 * number of IPPDEXPCR register cells, and "fsl,rcpm-wakeup"
> > @@ -139,10 +146,19 @@ static const struct of_device_id rcpm_of_match[]
> = {
> >   };
> >   MODULE_DEVICE_TABLE(of, rcpm_of_match);
> >
> > +#ifdef CONFIG_ACPI
> > +static const struct acpi_device_id rcpm_acpi_match[] = {
> > +	{ "NXP0015", },
> > +	{ }
> > +};
> > +MODULE_DEVICE_TABLE(acpi, rcpm_acpi_match); #endif
> > +
> >   static struct platform_driver rcpm_driver = {
> >   	.driver = {
> >   		.name = "rcpm",
> >   		.of_match_table = rcpm_of_match,
> > +		.acpi_match_table = ACPI_PTR(rcpm_acpi_match),
> >   		.pm	= &rcpm_pm_ops,
> >   	},
> >   	.probe = rcpm_probe,
> >