Revert "ACPI: Pass the same capabilities to the _OSC regardless of the query flag"

Revert commit 159d8c274fd9 ("ACPI: Pass the same capabilities to the
_OSC regardless of the query flag") which caused legitimate usage
scenarios (when the platform firmware does not want the OS to control
certain platform features controlled by the system bus scope _OSC) to
break and was misguided by some misleading language in the _OSC
definition in the ACPI specification (in particular, Section 6.2.11.1.3
"Sequence of _OSC Calls" that contradicts other perts of the _OSC
definition).

Link: https://lore.kernel.org/linux-acpi/CAJZ5v0iStA0JmO0H3z+VgQsVuQONVjKPpw0F5HKfiq=Gb6B5yw@mail.gmail.com
Reported-by: Mario Limonciello <Mario.Limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mario Limonciello <mario.limonciello@amd.com>
Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index 647791d34c19ffd43bbbd51e4d3993ef65fc3533..c7670d441ad9e133c722549ecdb5fdd0c5b5016d 100644 (file)
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -332,21 +332,32 @@ static void acpi_bus_osc_negotiate_platform_control(void)
        if (ACPI_FAILURE(acpi_run_osc(handle, &context)))
                return;
 
-       kfree(context.ret.pointer);
+       capbuf_ret = context.ret.pointer;
+       if (context.ret.length <= OSC_SUPPORT_DWORD) {
+               kfree(context.ret.pointer);
+               return;
+       }
 
-       /* Now run _OSC again with query flag clear */
+       /*
+        * Now run _OSC again with query flag clear and with the caps
+        * supported by both the OS and the platform.
+        */
        capbuf[OSC_QUERY_DWORD] = 0;
+       capbuf[OSC_SUPPORT_DWORD] = capbuf_ret[OSC_SUPPORT_DWORD];
+       kfree(context.ret.pointer);
 
        if (ACPI_FAILURE(acpi_run_osc(handle, &context)))
                return;
 
        capbuf_ret = context.ret.pointer;
-       osc_sb_apei_support_acked =
-               capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_APEI_SUPPORT;
-       osc_pc_lpi_support_confirmed =
-               capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_PCLPI_SUPPORT;
-       osc_sb_native_usb4_support_confirmed =
-               capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_NATIVE_USB4_SUPPORT;
+       if (context.ret.length > OSC_SUPPORT_DWORD) {
+               osc_sb_apei_support_acked =
+                       capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_APEI_SUPPORT;
+               osc_pc_lpi_support_confirmed =
+                       capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_PCLPI_SUPPORT;
+               osc_sb_native_usb4_support_confirmed =
+                       capbuf_ret[OSC_SUPPORT_DWORD] & OSC_SB_NATIVE_USB4_SUPPORT;
+       }
 
        kfree(context.ret.pointer);
 }