tools/power turbostat: Fix /dev/cpu_dma_latency warnings

[ Upstream commit 40aafc7d58d3544f152a863a0e9863014b6d5d8c ]

When running as non-root the following error is seen in turbostat:

turbostat: fopen /dev/cpu_dma_latency
: Permission denied

turbostat and the man page have information on how to avoid other
permission errors, so these can be fixed the same way.

Provide better /dev/cpu_dma_latency warnings that provide instructions on
how to avoid the error, and update the man page.

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: linux-pm@vger.kernel.org
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/power/x86/turbostat/turbostat.8 b/tools/power/x86/turbostat/turbostat.8
index c7b26a3..3e1a4c4 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.8
+++ b/tools/power/x86/turbostat/turbostat.8
@@ -344,6 +344,8 @@ Alternatively, non-root users can be enabled to run turbostat this way:
 
 # chmod +r /dev/cpu/*/msr
 
+# chmod +r /dev/cpu_dma_latency
+
 .B "turbostat "
 reads hardware counters, but doesn't write them.
 So it will not interfere with the OS or other programs, including

diff --git a/tools/power/x86/turbostat/turbostat.c b/tools/power/x86/turbostat/turbostat.c
index aba4604..c24054e 100644 (file)
--- a/tools/power/x86/turbostat/turbostat.c
+++ b/tools/power/x86/turbostat/turbostat.c
@@ -5482,7 +5482,7 @@ void print_dev_latency(void)
 
        retval = read(fd, (void *)&value, sizeof(int));
        if (retval != sizeof(int)) {
-               warn("read %s\n", path);
+               warn("read failed %s\n", path);
                close(fd);
                return;
        }