linux-kernel - [PATCH v4 6/6] stm class: ftrace: use different channel accroding to CPU

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Message-Id: <20200926010005.14689-7-tingwei@codeaurora.org>
Date:   Sat, 26 Sep 2020 09:00:05 +0800
From:   Tingwei Zhang <tingwei@...eaurora.org>
To:     Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>
Cc:     Tingwei Zhang <tingwei@...eaurora.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        tsoni@...eaurora.org,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Mao Jinlong <jinlmao@...eaurora.org>,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v4 6/6] stm class: ftrace: use different channel accroding to CPU

To avoid mixup of packets from differnt ftrace packets simultaneously,
use different channel for packets from different CPU.

Signed-off-by: Tingwei Zhang <tingwei@...eaurora.org>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 drivers/hwtracing/stm/ftrace.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/hwtracing/stm/ftrace.c b/drivers/hwtracing/stm/ftrace.c
index c694a6e692d1..3bb606dfa634 100644
--- a/drivers/hwtracing/stm/ftrace.c
+++ b/drivers/hwtracing/stm/ftrace.c
@@ -37,8 +37,10 @@ static void notrace
 stm_ftrace_write(struct trace_export *export, const void *buf, unsigned int len)
 {
 	struct stm_ftrace *stm = container_of(export, struct stm_ftrace, ftrace);
+	/* This is called from trace system with preemption disabled */
+	unsigned int cpu = smp_processor_id();
 
-	stm_source_write(&stm->data, STM_FTRACE_CHAN, buf, len);
+	stm_source_write(&stm->data, STM_FTRACE_CHAN + cpu, buf, len);
 }
 
 static int stm_ftrace_link(struct stm_source_data *data)
@@ -63,6 +65,7 @@ static int __init stm_ftrace_init(void)
 {
 	int ret;
 
+	stm_ftrace.data.nr_chans = roundup_pow_of_two(num_possible_cpus());
 	ret = stm_source_register_device(NULL, &stm_ftrace.data);
 	if (ret)
 		pr_err("Failed to register stm_source - ftrace.\n");
-- 
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