linux-kernel - [PATCH] power: supply: surface_battery: Fix battery event handling

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Message-Id: <20210504184813.3414376-1-luzmaximilian@gmail.com>
Date:   Tue,  4 May 2021 20:48:13 +0200
From:   Maximilian Luz <luzmaximilian@...il.com>
To:     Sebastian Reichel <sre@...nel.org>
Cc:     Maximilian Luz <luzmaximilian@...il.com>, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] power: supply: surface_battery: Fix battery event handling

The battery subsystem of the Surface Aggregator Module EC requires us to
register the battery notifier with instance ID 0. However, battery
events are actually sent with the instance ID corresponding to the
device, which is nonzero. Thus, the strict-matching approach doesn't
work here and will discard events that the driver is expected to handle.

To fix this we have to fall back on notifier matching by target-category
only and have to manually check the instance ID in the notifier
callback.

Fixes: 167f77f7d0b3 ("power: supply: Add battery driver for Surface Aggregator Module")
Signed-off-by: Maximilian Luz <luzmaximilian@...il.com>
---
 drivers/power/supply/surface_battery.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/power/supply/surface_battery.c b/drivers/power/supply/surface_battery.c
index 7efa431a62b2..5ec2e6bb2465 100644
--- a/drivers/power/supply/surface_battery.c
+++ b/drivers/power/supply/surface_battery.c
@@ -345,6 +345,16 @@ static u32 spwr_notify_bat(struct ssam_event_notifier *nf, const struct ssam_eve
 	struct spwr_battery_device *bat = container_of(nf, struct spwr_battery_device, notif);
 	int status;
 
+	/*
+	 * We cannot use strict matching when registering the notifier as the
+	 * EC expects us to register it against instance ID 0. Strict matching
+	 * would thus drop events, as those may have non-zero instance IDs in
+	 * this subsystem. So we need to check the instance ID of the event
+	 * here manually.
+	 */
+	if (event->instance_id != bat->sdev->uid.instance)
+		return 0;
+
 	dev_dbg(&bat->sdev->dev, "power event (cid = %#04x, iid = %#04x, tid = %#04x)\n",
 		event->command_id, event->instance_id, event->target_id);
 
@@ -720,8 +730,8 @@ static void spwr_battery_init(struct spwr_battery_device *bat, struct ssam_devic
 	bat->notif.base.fn = spwr_notify_bat;
 	bat->notif.event.reg = registry;
 	bat->notif.event.id.target_category = sdev->uid.category;
-	bat->notif.event.id.instance = 0;
-	bat->notif.event.mask = SSAM_EVENT_MASK_STRICT;
+	bat->notif.event.id.instance = 0;	/* need to register with instance 0 */
+	bat->notif.event.mask = SSAM_EVENT_MASK_TARGET;
 	bat->notif.event.flags = SSAM_EVENT_SEQUENCED;
 
 	bat->psy_desc.name = bat->name;
-- 
2.31.1