[PATCH] coresight: etm4x: lazily allocate memory for save_state

From: Andrew Murray <andrew.murray@arm.com>
To: Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: coresight@lists.linaro.org, Sudeep Holla <sudeep.holla@arm.com>,
	Leo Yan <leo.yan@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	Mike Leach <mike.leach@linaro.org>
Subject: [PATCH] coresight: etm4x: lazily allocate memory for save_state
Date: Fri, 12 Jul 2019 16:00:56 +0100	[thread overview]
Message-ID: <20190712150056.15775-1-andrew.murray@arm.com> (raw)
In-Reply-To: <20190711160114.634-6-andrew.murray@arm.com>

I had intended to lazily allocate memory for the save_state structure when
it is first used. Following is a patch that I will squash into "[PATCH v3 5/6]
coresight: etm4x: save/restore state across CPU low power states" on my
next respin. I thought I'd share it here to get some feedback along with
the rest of v3.

Thanks,

Andrew Murray

---
 drivers/hwtracing/coresight/coresight-etm4x.c | 14 +++++++++++---
 drivers/hwtracing/coresight/coresight-etm4x.h |  2 +-
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index b0bd8158bf13..cd02372194bc 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x.c
@@ -1112,6 +1112,13 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 	struct etmv4_save_state *state;
 	struct device *etm_dev = &drvdata->csdev->dev;
 
+	if (!drvdata->save_state) {
+		drvdata->save_state = devm_kmalloc(etm_dev,
+				sizeof(struct etmv4_save_state), GFP_KERNEL);
+		if (!drvdata->save_state)
+			return -ENOMEM;
+	}
+
 	/*
 	 * As recommended by 3.4.1 ("The procedure when powering down the PE")
 	 * of ARM IHI 0064D
@@ -1134,7 +1141,7 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 		goto out;
 	}
 
-	state = &drvdata->save_state;
+	state = drvdata->save_state;
 
 	state->trcprgctlr = readl(drvdata->base + TRCPRGCTLR);
 	state->trcprocselr = readl(drvdata->base + TRCPROCSELR);
@@ -1234,9 +1241,10 @@ static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
 static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
 {
 	int i;
-	struct etmv4_save_state *state;
+	struct etmv4_save_state *state = drvdata->save_state;
 
-	state = &drvdata->save_state;
+	if (WARN_ON_ONCE(!state))
+		return;
 
 	CS_UNLOCK(drvdata->base);
 
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index c31634c64f87..a70cafbbb8cf 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -441,7 +441,7 @@ struct etmv4_drvdata {
 	bool				atbtrig;
 	bool				lpoverride;
 	struct etmv4_config		config;
-	struct etmv4_save_state		save_state;
+	struct etmv4_save_state		*save_state;
 	bool				state_needs_restore;
 };
 
-- 
2.21.0


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