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From:   Mikko Perttunen <cyndis@kapsi.fi>
To:     "Rafael J. Wysocki" <rafael@kernel.org>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Amit Kucheria <amitk@kernel.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>
Cc:     Mikko Perttunen <mperttunen@nvidia.com>, linux-pm@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2] thermal: tegra-bpmp: Handle offline zones
Date:   Thu, 30 Mar 2023 12:49:04 +0300
Message-Id: <20230330094904.2589428-1-cyndis@kapsi.fi>
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From: Mikko Perttunen <mperttunen@nvidia.com>

Thermal zones located in power domains may not be accessible when
the domain is powergated. In this situation, reading the temperature
will return -BPMP_EFAULT. When evaluating trips, BPMP will internally
use -256C as the temperature for offline zones.

For smooth operation, for offline zones, return -EAGAIN when reading
the temperature and allow registration of zones even if they are
offline during probe.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
---
v2:
* Adjusted commit message.
* Patch 2/2 dropped for now since it is more controversial,
  and this patch is more critical.

 drivers/thermal/tegra/tegra-bpmp-thermal.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/tegra/tegra-bpmp-thermal.c b/drivers/thermal/tegra/tegra-bpmp-thermal.c
index f5fd4018f72f..4ffc3bb3bf35 100644
--- a/drivers/thermal/tegra/tegra-bpmp-thermal.c
+++ b/drivers/thermal/tegra/tegra-bpmp-thermal.c
@@ -52,6 +52,8 @@ static int __tegra_bpmp_thermal_get_temp(struct tegra_bpmp_thermal_zone *zone,
 	err = tegra_bpmp_transfer(zone->tegra->bpmp, &msg);
 	if (err)
 		return err;
+	if (msg.rx.ret == -BPMP_EFAULT)
+		return -EAGAIN;
 	if (msg.rx.ret)
 		return -EINVAL;
 
@@ -259,7 +261,12 @@ static int tegra_bpmp_thermal_probe(struct platform_device *pdev)
 		zone->tegra = tegra;
 
 		err = __tegra_bpmp_thermal_get_temp(zone, &temp);
-		if (err < 0) {
+
+		/*
+		 * Sensors in powergated domains may temporarily fail to be read
+		 * (-EAGAIN), but will become accessible when the domain is powered on.
+		 */
+		if (err < 0 && err != -EAGAIN) {
 			devm_kfree(&pdev->dev, zone);
 			continue;
 		}
-- 
2.39.2