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

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Date:	Mon, 24 Nov 2014 17:32:33 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	Lee Jones <lee.jones@...aro.org>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Yegnesh Iyer <yegnesh.s.iyer@...el.com>,
	linux-acpi@...r.kernel.org, linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 updated 3/3] ACPI / PMIC: AXP288: support virtual GPIO
 in ACPI table

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a no longer valid memory place.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.

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 = {
-- 
1.9.3

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