linux-kernel - RE: [PATCH v3 updated 3/3] ACPI / PMIC: AXP288: support virtual GPIO in ACPI table

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Date:	Tue, 25 Nov 2014 01:44:28 +0000
From:	"Zheng, Lv" <lv.zheng@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"Lu, Aaron" <aaron.lu@...el.com>
CC:	Lee Jones <lee.jones@...aro.org>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	"Iyer, Yegnesh S" <yegnesh.s.iyer@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v3 updated 3/3] ACPI / PMIC: AXP288: support virtual
 GPIO in ACPI table

Hi,

> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> Sent: Monday, November 24, 2014 11:20 PM
> Lv
> Subject: Re: [PATCH v3 updated 3/3] ACPI / PMIC: AXP288: support virtual GPIO in ACPI table
> 
> On Monday, November 24, 2014 05:32:33 PM Aaron Lu wrote:
> > On 11/24/2014 09:06 AM, Rafael J. Wysocki wrote:
> > > On Friday, November 21, 2014 03:11:51 PM Aaron Lu wrote:
> > >> +	if (!result) {
> > >> +		status = acpi_install_address_space_handler(
> > >> +				ACPI_HANDLE(parent), ACPI_ADR_SPACE_GPIO,
> > >> +				intel_xpower_pmic_gpio_handler, NULL, NULL);
> > >
> > > So here we have a problem, because we can't unregister the opregion handler
> > > registered above if this fails.  Not nice.
> >
> > I'm not correct in the cover letter, the actual problem with operation
> > region remove is with module unload, it happens like this:
> >
> > The acpi_remove_address_space_handler doesn't wait for the current
> > running handler to return, so if we call
> > acpi_remove_address_space_handler in a module's exit function, the
> > handler's memory will be freed and the running handler will access to
> > a no longer valid memory place.
> >
> > So as long as we can make sure the handler will not go away from the
> > memory, we are safe.
> 
> This only means that address space handlers cannot be removed from kernel
> modules.
> 
> Lv was trying to add a wrapper for that some time ago, maybe it's a good
> idea to revive that?

I may fix the issue in ACPICA, but it looks like that it will cost time to discuss.
So I also think it is better to take the wrapper now.
I'll hand the patch to Aaron to let him do a test on it before posting it again.

Thanks and best regards
-Lv

> > With this said, the updated patch is here:
> >
> > From: Aaron Lu <aaron.lu@...el.com>
> > Date: Mon, 20 Oct 2014 17:06:20 +0800
> > Subject: [PATCH 3/3] ACPI / PMIC: AXP288: support virtual GPIO in ACPI table
> >
> > The same virtual GPIO strategy is also used for the AXP288 PMIC in that
> > various control methods that are used to do power rail handling and
> > sensor reading/setting will touch GPIO fields defined under the PMIC
> > device. The GPIO fileds are only defined by the ACPI code while the
> > actual hardware doesn't really have a GPIO controller, but to make those
> > control method execution succeed, we have to install a GPIO handler for
> > the PMIC device handle. Since we do not need the virtual GPIO strategy,
> > we can simply do nothing in that handler.
> >
> > Signed-off-by: Aaron Lu <aaron.lu@...el.com>
> > ---
> >  drivers/acpi/pmic/intel_pmic_xpower.c | 30 ++++++++++++++++++++++++++----
> >  1 file changed, 26 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/acpi/pmic/intel_pmic_xpower.c b/drivers/acpi/pmic/intel_pmic_xpower.c
> > index 795ca073db08..9ec57ebd81c9 100644
> > --- a/drivers/acpi/pmic/intel_pmic_xpower.c
> > +++ b/drivers/acpi/pmic/intel_pmic_xpower.c
> > @@ -220,13 +220,35 @@ static struct intel_pmic_opregion_data intel_xpower_pmic_opregion_data = {
> >  	.thermal_table_count = ARRAY_SIZE(thermal_table),
> >  };
> >
> > +static acpi_status intel_xpower_pmic_gpio_handler(u32 function,
> > +		acpi_physical_address address, u32 bit_width, u64 *value,
> > +		void *handler_context, void *region_context)
> > +{
> > +	return AE_OK;
> > +}
> >
> >  static int intel_xpower_pmic_opregion_probe(struct platform_device *pdev)
> >  {
> > -	struct axp20x_dev *axp20x = dev_get_drvdata(pdev->dev.parent);
> > -	return intel_pmic_install_opregion_handler(&pdev->dev,
> > -			ACPI_HANDLE(pdev->dev.parent), axp20x->regmap,
> > -			&intel_xpower_pmic_opregion_data);
> > +	struct device *parent = pdev->dev.parent;
> > +	struct axp20x_dev *axp20x = dev_get_drvdata(parent);
> > +	acpi_status status;
> > +	int result;
> > +
> > +	status = acpi_install_address_space_handler(ACPI_HANDLE(parent),
> > +			ACPI_ADR_SPACE_GPIO, intel_xpower_pmic_gpio_handler,
> > +			NULL, NULL);
> > +	if (ACPI_FAILURE(status))
> > +		return -ENODEV;
> > +
> > +	result = intel_pmic_install_opregion_handler(&pdev->dev,
> > +					ACPI_HANDLE(parent), axp20x->regmap,
> > +					&intel_xpower_pmic_opregion_data);
> > +	if (result)
> > +		acpi_remove_address_space_handler(ACPI_HANDLE(parent),
> > +						  ACPI_ADR_SPACE_GPIO,
> > +						  intel_xpower_pmic_gpio_handler);
> > +
> > +	return result;
> >  }
> >
> >  static struct platform_driver intel_xpower_pmic_opregion_driver = {
> >
> 
> --
> I speak only for myself.
> Rafael J. Wysocki, Intel Open Source Technology Center.