linux-kernel - [PATCH AUTOSEL 5.15 29/29] Revert "ACPI: Pass the same capabilities to the

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Date:   Mon, 28 Mar 2022 07:21:31 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Mario Limonciello <Mario.Limonciello@....com>,
        Mario Limonciello <mario.limonciello@....com>,
        Huang Rui <ray.huang@....com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Sasha Levin <sashal@...nel.org>, rafael@...nel.org,
        linux-acpi@...r.kernel.org
Subject: [PATCH AUTOSEL 5.15 29/29] Revert "ACPI: Pass the same capabilities to the _OSC regardless of the query flag"

From: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>

[ Upstream commit 2ca8e6285250c07a2e5a22ecbfd59b5a4ef73484 ]

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@....com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Tested-by: Mario Limonciello <mario.limonciello@....com>
Acked-by: Huang Rui <ray.huang@....com>
Reviewed-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/acpi/bus.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index dd535b4b9a16..3500744e6862 100644
--- 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);
 }
-- 
2.34.1