ACPI / LPSS: Only call pwm_add_table() for Bay Trail PWM if PMIC HRV is 2

jwrdegoede · rafaeljw · commit c975e472ec12 · 2018-05-10T16:54:40.000+02:00
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 &lt;hdegoede@redhat.com&gt;
Reviewed-by: Andy Shevchenko &lt;andriy.shevchenko@linux.intel.com&gt;
Signed-off-by: Rafael J. Wysocki &lt;rafael.j.wysocki@intel.com&gt;
diff --git a/drivers/acpi/acpi_lpss.c b/drivers/acpi/acpi_lpss.c
@@ -69,6 +69,10 @@ 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 {
@@ -162,7 +166,7 @@ static void byt_pwm_setup(struct lpss_private_data *pdata)
 	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));
 }
 
