[PATCH V2 1/5] dmaengine: dmatest: Add support for multi channel testing

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Add support for running tests on multiple channels simultaneously as the
driver currently limits to 1 channel per test run. This will add support
for stress testing DMA controllers with multi channel capabilities.

This is done by adding a callback function to the "channel" parameter
that registers the requested channel prior to the "run" parameter being
set to 1. Each time the "channel" parameter is populated with a new
dma channel, a new test is appended to the thread queue. Once the "run"
parameter is set to 1, the test will kick start all pending threads.

Signed-off-by: Seraj Alijan <seraj.alijan@xxxxxxxxxxx>
---
 drivers/dma/dmatest.c | 109 +++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 89 insertions(+), 20 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index aa1712b..8ce3b06 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -27,11 +27,6 @@ static unsigned int test_buf_size = 16384;
 module_param(test_buf_size, uint, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(test_buf_size, "Size of the memcpy test buffer");
 
-static char test_channel[20];
-module_param_string(channel, test_channel, sizeof(test_channel),
-		S_IRUGO | S_IWUSR);
-MODULE_PARM_DESC(channel, "Bus ID of the channel to test (default: any)");
-
 static char test_device[32];
 module_param_string(device, test_device, sizeof(test_device),
 		S_IRUGO | S_IWUSR);
@@ -139,6 +134,21 @@ static bool dmatest_run;
 module_param_cb(run, &run_ops, &dmatest_run, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(run, "Run the test (default: false)");
 
+static int dmatest_chan_set(const char *val, const struct kernel_param *kp);
+static int dmatest_chan_get(char *val, const struct kernel_param *kp);
+static const struct kernel_param_ops multi_chan_ops = {
+	.set = dmatest_chan_set,
+	.get = dmatest_chan_get,
+};
+
+static char test_channel[20];
+static struct kparam_string newchan_kps = {
+	.string = test_channel,
+	.maxlen = 20,
+};
+module_param_cb(channel, &multi_chan_ops, &newchan_kps, 0644);
+MODULE_PARM_DESC(channel, "Bus ID of the channel to test (default: any)");
+
 /* Maximum amount of mismatched bytes in buffer to print */
 #define MAX_ERROR_COUNT		32
 
@@ -179,6 +189,7 @@ struct dmatest_thread {
 	wait_queue_head_t done_wait;
 	struct dmatest_done test_done;
 	bool			done;
+	bool			pending;
 };
 
 struct dmatest_chan {
@@ -206,6 +217,22 @@ static bool is_threaded_test_run(struct dmatest_info *info)
 	return false;
 }
 
+static bool is_threaded_test_pending(struct dmatest_info *info)
+{
+	struct dmatest_chan *dtc;
+
+	list_for_each_entry(dtc, &info->channels, node) {
+		struct dmatest_thread *thread;
+
+		list_for_each_entry(thread, &dtc->threads, node) {
+			if (thread->pending)
+				return true;
+		}
+	}
+
+	return false;
+}
+
 static int dmatest_wait_get(char *val, const struct kernel_param *kp)
 {
 	struct dmatest_info *info = &test_info;
@@ -476,6 +503,7 @@ static int dmatest_func(void *data)
 	ret = -ENOMEM;
 
 	smp_rmb();
+	thread->pending = false;
 	info = thread->info;
 	params = &info->params;
 	chan = thread->chan;
@@ -886,7 +914,7 @@ static int dmatest_add_threads(struct dmatest_info *info,
 		/* srcbuf and dstbuf are allocated by the thread itself */
 		get_task_struct(thread->task);
 		list_add_tail(&thread->node, &dtc->threads);
-		wake_up_process(thread->task);
+		thread->pending = true;
 	}
 
 	return i;
@@ -932,7 +960,7 @@ static int dmatest_add_channel(struct dmatest_info *info,
 		thread_count += cnt > 0 ? cnt : 0;
 	}
 
-	pr_info("Started %u threads using %s\n",
+	pr_info("Added %u threads using %s\n",
 		thread_count, dma_chan_name(chan));
 
 	list_add_tail(&dtc->node, &info->channels);
@@ -977,7 +1005,7 @@ static void request_channels(struct dmatest_info *info,
 	}
 }
 
-static void run_threaded_test(struct dmatest_info *info)
+static void add_threaded_test(struct dmatest_info *info)
 {
 	struct dmatest_params *params = &info->params;
 
@@ -1000,6 +1028,19 @@ static void run_threaded_test(struct dmatest_info *info)
 	request_channels(info, DMA_PQ);
 }
 
+static void run_pending_tests(struct dmatest_info *info)
+{
+	struct dmatest_chan *dtc;
+
+	list_for_each_entry(dtc, &info->channels, node) {
+		struct dmatest_thread *thread;
+
+		list_for_each_entry(thread, &dtc->threads, node) {
+			wake_up_process(thread->task);
+		}
+	}
+}
+
 static void stop_threaded_test(struct dmatest_info *info)
 {
 	struct dmatest_chan *dtc, *_dtc;
@@ -1016,7 +1057,7 @@ static void stop_threaded_test(struct dmatest_info *info)
 	info->nr_channels = 0;
 }
 
-static void restart_threaded_test(struct dmatest_info *info, bool run)
+static void start_threaded_tests(struct dmatest_info *info)
 {
 	/* we might be called early to set run=, defer running until all
 	 * parameters have been evaluated
@@ -1024,11 +1065,7 @@ static void restart_threaded_test(struct dmatest_info *info, bool run)
 	if (!info->did_init)
 		return;
 
-	/* Stop any running test first */
-	stop_threaded_test(info);
-
-	/* Run test with new parameters */
-	run_threaded_test(info);
+	run_pending_tests(info);
 }
 
 static int dmatest_run_get(char *val, const struct kernel_param *kp)
@@ -1039,7 +1076,8 @@ static int dmatest_run_get(char *val, const struct kernel_param *kp)
 	if (is_threaded_test_run(info)) {
 		dmatest_run = true;
 	} else {
-		stop_threaded_test(info);
+		if (!is_threaded_test_pending(info))
+			stop_threaded_test(info);
 		dmatest_run = false;
 	}
 	mutex_unlock(&info->lock);
@@ -1057,18 +1095,48 @@ static int dmatest_run_set(const char *val, const struct kernel_param *kp)
 	if (ret) {
 		mutex_unlock(&info->lock);
 		return ret;
+	} else if (dmatest_run && is_threaded_test_pending(info)) {
+		start_threaded_tests(info);
 	}
 
-	if (is_threaded_test_run(info))
-		ret = -EBUSY;
-	else if (dmatest_run)
-		restart_threaded_test(info, dmatest_run);
+	mutex_unlock(&info->lock);
+
+	return ret;
+}
+
+static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
+{
+	struct dmatest_info *info = &test_info;
+	int ret;
 
+	mutex_lock(&info->lock);
+	ret = param_set_copystring(val, kp);
+	if (ret) {
+		mutex_unlock(&info->lock);
+		return ret;
+	}
+	if (!is_threaded_test_run(info) && !is_threaded_test_pending(info))
+		stop_threaded_test(info);
+	add_threaded_test(info);
 	mutex_unlock(&info->lock);
 
 	return ret;
 }
 
+static int dmatest_chan_get(char *val, const struct kernel_param *kp)
+{
+	struct dmatest_info *info = &test_info;
+
+	mutex_lock(&info->lock);
+	if (!is_threaded_test_run(info) && !is_threaded_test_pending(info)) {
+		stop_threaded_test(info);
+		strlcpy(test_channel, "", sizeof(test_channel));
+	}
+	mutex_unlock(&info->lock);
+
+	return param_get_string(val, kp);
+}
+
 static int __init dmatest_init(void)
 {
 	struct dmatest_info *info = &test_info;
@@ -1076,7 +1144,8 @@ static int __init dmatest_init(void)
 
 	if (dmatest_run) {
 		mutex_lock(&info->lock);
-		run_threaded_test(info);
+		add_threaded_test(info);
+		run_pending_tests(info);
 		mutex_unlock(&info->lock);
 	}
 
-- 
2.7.4




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