linux-kernel - [PATCH 4.17 200/336] ACPI / LPSS: Only call pwm_add_table() for Bay Trail PWM if PMIC HRV is 2

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Date:   Wed,  1 Aug 2018 18:48:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.17 200/336] ACPI / LPSS: Only call pwm_add_table() for Bay Trail PWM if PMIC HRV is 2

4.17-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hans de Goede <hdegoede@...hat.com>

[ Upstream commit c975e472ec12392a0c34de1350e634310f8a1dea ]

The Point of View mobii wintab p800w Bay Trail tablet comes with a Crystal
Cove PMIC, yet uses the LPSS PWM for backlight control, rather then the
Crystal Cove's PWM, so we need to call pwm_add_table() to add a
pwm_backlight mapping for the LPSS pwm despite there being an INT33FD
ACPI device present.

On all Bay Trail devices the _HRV object of the INT33FD ACPI device
will normally return 2, to indicate the Bay Trail variant of the CRC
PMIC is present, except on this tablet where _HRV is 0xffff. I guess this
is a hack to make the windows Crystal Cove PWM driver not bind.

Out of the 44 DSTDs with an INT33FD device in there which I have (from
different model devices) only the pov mobii wintab p800w uses 0xffff for
the HRV.

The byt_pwm_setup code calls acpi_dev_present to check for the presence
of a INT33FD ACPI device which indicates that a CRC PMIC is present and
if the INT33FD ACPI device is present then byt_pwm_setup will not add
a pwm_backlight mapping for the LPSS pwm, so that the CRC PWM will get
used instead.

acpi_dev_present has a hrv parameter, this commit make us pass 2 instead
of -1, so that things still match on normal tablets, but on this special
case with its _HRV of 0xffff, the check will now fail so that the
pwm_backlight mapping for the LPSS pwm gets added fixing backlight
brightness control on this device.

Signed-off-by: Hans de Goede <hdegoede@...hat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/acpi/acpi_lpss.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/acpi/acpi_lpss.c
+++ b/drivers/acpi/acpi_lpss.c
@@ -70,6 +70,10 @@ ACPI_MODULE_NAME("acpi_lpss");
 #define LPSS_SAVE_CTX			BIT(4)
 #define LPSS_NO_D3_DELAY		BIT(5)

+/* Crystal Cove PMIC shares same ACPI ID between different platforms */
+#define BYT_CRC_HRV			2
+#define CHT_CRC_HRV			3
+
 struct lpss_private_data;

 struct lpss_device_desc {
@@ -163,7 +167,7 @@ static void byt_pwm_setup(struct lpss_pr
 	if (!adev->pnp.unique_id || strcmp(adev->pnp.unique_id, "1"))
 		return;

-	if (!acpi_dev_present("INT33FD", NULL, -1))
+	if (!acpi_dev_present("INT33FD", NULL, BYT_CRC_HRV))
 		pwm_add_table(byt_pwm_lookup, ARRAY_SIZE(byt_pwm_lookup));
 }