coresight: tmc: Cleanup operation mode handling

The mode of operation of the TMC tracked in drvdata->mode is defined
as a local_t type. This is always checked and modified under the
drvdata->spinlock and hence we don't need local_t for it and the
unnecessary synchronisation instructions that comes with it. This
change makes the code a bit more cleaner.

Also fixes the order in which we update the drvdata->mode to
CS_MODE_DISABLED. i.e, in tmc_disable_etX_sink we change the
mode to CS_MODE_DISABLED before invoking tmc_disable_etX_hw()
which in turn depends on the mode to decide whether to dump the
trace to a buffer.

Applies on mathieu's coresight/next tree [1]

https://git.linaro.org/kernel/coresight.git next
Reported-by: Venkatesh Vivekanandan <venkatesh.vivekanandan@broadcom.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hwtracing/coresight/coresight-tmc-etf.c

@@ -70,7 +70,7 @@ static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
 	 * When operating in sysFS mode the content of the buffer needs to be
 	 * read before the TMC is disabled.
 	 */
-	if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		tmc_etb_dump_hw(drvdata);
 	tmc_disable_hw(drvdata);
 
@@ -108,7 +108,6 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev, u32 mode)
 	int ret = 0;
 	bool used = false;
 	char *buf = NULL;
-	long val;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -138,13 +137,12 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev, u32 mode)
 		goto out;
 	}
 
-	val = local_xchg(&drvdata->mode, mode);
 	/*
 	 * In sysFS mode we can have multiple writers per sink.  Since this
 	 * sink is already enabled no memory is needed and the HW need not be
 	 * touched.
 	 */
-	if (val == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		goto out;
 
 	/*
@@ -163,6 +161,7 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev, u32 mode)
 		drvdata->buf = buf;
 	}
 
+	drvdata->mode = CS_MODE_SYSFS;
 	tmc_etb_enable_hw(drvdata);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -180,7 +179,6 @@ static int tmc_enable_etf_sink_sysfs(struct coresight_device *csdev, u32 mode)
 static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, u32 mode)
 {
 	int ret = 0;
-	long val;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -194,17 +192,17 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, u32 mode)
 		goto out;
 	}
 
-	val = local_xchg(&drvdata->mode, mode);
 	/*
 	 * In Perf mode there can be only one writer per sink.  There
 	 * is also no need to continue if the ETB/ETR is already operated
 	 * from sysFS.
 	 */
-	if (val != CS_MODE_DISABLED) {
+	if (drvdata->mode != CS_MODE_DISABLED) {
 		ret = -EINVAL;
 		goto out;
 	}
 
+	drvdata->mode = mode;
 	tmc_etb_enable_hw(drvdata);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -227,7 +225,6 @@ static int tmc_enable_etf_sink(struct coresight_device *csdev, u32 mode)
 
 static void tmc_disable_etf_sink(struct coresight_device *csdev)
 {
-	long val;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -237,10 +234,11 @@ static void tmc_disable_etf_sink(struct coresight_device *csdev)
 		return;
 	}
 
-	val = local_xchg(&drvdata->mode, CS_MODE_DISABLED);
 	/* Disable the TMC only if it needs to */
-	if (val != CS_MODE_DISABLED)
+	if (drvdata->mode != CS_MODE_DISABLED) {
 		tmc_etb_disable_hw(drvdata);
+		drvdata->mode = CS_MODE_DISABLED;
+	}
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -260,7 +258,7 @@ static int tmc_enable_etf_link(struct coresight_device *csdev,
 	}
 
 	tmc_etf_enable_hw(drvdata);
-	local_set(&drvdata->mode, CS_MODE_SYSFS);
+	drvdata->mode = CS_MODE_SYSFS;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_info(drvdata->dev, "TMC-ETF enabled\n");
@@ -280,7 +278,7 @@ static void tmc_disable_etf_link(struct coresight_device *csdev,
 	}
 
 	tmc_etf_disable_hw(drvdata);
-	local_set(&drvdata->mode, CS_MODE_DISABLED);
+	drvdata->mode = CS_MODE_DISABLED;
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
 	dev_info(drvdata->dev, "TMC disabled\n");
@@ -383,7 +381,7 @@ static void tmc_update_etf_buffer(struct coresight_device *csdev,
 		return;
 
 	/* This shouldn't happen */
-	if (WARN_ON_ONCE(local_read(&drvdata->mode) != CS_MODE_PERF))
+	if (WARN_ON_ONCE(drvdata->mode != CS_MODE_PERF))
 		return;
 
 	CS_UNLOCK(drvdata->base);
@@ -504,7 +502,6 @@ const struct coresight_ops tmc_etf_cs_ops = {
 
 int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 {
-	long val;
 	enum tmc_mode mode;
 	int ret = 0;
 	unsigned long flags;
@@ -528,9 +525,8 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 		goto out;
 	}
 
-	val = local_read(&drvdata->mode);
 	/* Don't interfere if operated from Perf */
-	if (val == CS_MODE_PERF) {
+	if (drvdata->mode == CS_MODE_PERF) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -542,7 +538,7 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata)
 	}
 
 	/* Disable the TMC if need be */
-	if (val == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		tmc_etb_disable_hw(drvdata);
 
 	drvdata->reading = true;
@@ -573,7 +569,7 @@ int tmc_read_unprepare_etb(struct tmc_drvdata *drvdata)
 	}
 
 	/* Re-enable the TMC if need be */
-	if (local_read(&drvdata->mode) == CS_MODE_SYSFS) {
+	if (drvdata->mode == CS_MODE_SYSFS) {
 		/*
 		 * The trace run will continue with the same allocated trace
 		 * buffer. As such zero-out the buffer so that we don't end

drivers/hwtracing/coresight/coresight-tmc-etr.c

@@ -86,7 +86,7 @@ static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
 	 * When operating in sysFS mode the content of the buffer needs to be
 	 * read before the TMC is disabled.
 	 */
-	if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		tmc_etr_dump_hw(drvdata);
 	tmc_disable_hw(drvdata);
 
@@ -97,7 +97,6 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev, u32 mode)
 {
 	int ret = 0;
 	bool used = false;
-	long val;
 	unsigned long flags;
 	void __iomem *vaddr = NULL;
 	dma_addr_t paddr;
@@ -134,13 +133,12 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev, u32 mode)
 		goto out;
 	}
 
-	val = local_xchg(&drvdata->mode, mode);
 	/*
 	 * In sysFS mode we can have multiple writers per sink.  Since this
 	 * sink is already enabled no memory is needed and the HW need not be
 	 * touched.
 	 */
-	if (val == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		goto out;
 
 	/*
@@ -157,6 +155,7 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev, u32 mode)
 
 	memset(drvdata->vaddr, 0, drvdata->size);
 
+	drvdata->mode = CS_MODE_SYSFS;
 	tmc_etr_enable_hw(drvdata);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -174,7 +173,6 @@ static int tmc_enable_etr_sink_sysfs(struct coresight_device *csdev, u32 mode)
 static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, u32 mode)
 {
 	int ret = 0;
-	long val;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -188,17 +186,17 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, u32 mode)
 		goto out;
 	}
 
-	val = local_xchg(&drvdata->mode, mode);
 	/*
 	 * In Perf mode there can be only one writer per sink.  There
 	 * is also no need to continue if the ETR is already operated
 	 * from sysFS.
 	 */
-	if (val != CS_MODE_DISABLED) {
+	if (drvdata->mode != CS_MODE_DISABLED) {
 		ret = -EINVAL;
 		goto out;
 	}
 
+	drvdata->mode = CS_MODE_PERF;
 	tmc_etr_enable_hw(drvdata);
 out:
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -221,7 +219,6 @@ static int tmc_enable_etr_sink(struct coresight_device *csdev, u32 mode)
 
 static void tmc_disable_etr_sink(struct coresight_device *csdev)
 {
-	long val;
 	unsigned long flags;
 	struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
 
@@ -231,10 +228,11 @@ static void tmc_disable_etr_sink(struct coresight_device *csdev)
 		return;
 	}
 
-	val = local_xchg(&drvdata->mode, CS_MODE_DISABLED);
 	/* Disable the TMC only if it needs to */
-	if (val != CS_MODE_DISABLED)
+	if (drvdata->mode != CS_MODE_DISABLED) {
 		tmc_etr_disable_hw(drvdata);
+		drvdata->mode = CS_MODE_DISABLED;
+	}
 
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
@@ -253,7 +251,6 @@ const struct coresight_ops tmc_etr_cs_ops = {
 int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 {
 	int ret = 0;
-	long val;
 	unsigned long flags;
 
 	/* config types are set a boot time and never change */
@@ -266,9 +263,8 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 		goto out;
 	}
 
-	val = local_read(&drvdata->mode);
 	/* Don't interfere if operated from Perf */
-	if (val == CS_MODE_PERF) {
+	if (drvdata->mode == CS_MODE_PERF) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -280,7 +276,7 @@ int tmc_read_prepare_etr(struct tmc_drvdata *drvdata)
 	}
 
 	/* Disable the TMC if need be */
-	if (val == CS_MODE_SYSFS)
+	if (drvdata->mode == CS_MODE_SYSFS)
 		tmc_etr_disable_hw(drvdata);
 
 	drvdata->reading = true;
@@ -303,7 +299,7 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata)
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 
 	/* RE-enable the TMC if need be */
-	if (local_read(&drvdata->mode) == CS_MODE_SYSFS) {
+	if (drvdata->mode == CS_MODE_SYSFS) {
 		/*
 		 * The trace run will continue with the same allocated trace
 		 * buffer. The trace buffer is cleared in tmc_etr_enable_hw(),

drivers/hwtracing/coresight/coresight-tmc.h

@@ -117,7 +117,7 @@ struct tmc_drvdata {
 	void __iomem		*vaddr;
 	u32			size;
 	u32			len;
-	local_t			mode;
+	u32			mode;
 	enum tmc_config_type	config_type;
 	enum tmc_mem_intf_width	memwidth;
 	u32			trigger_cntr;