Hi Mathieu,
On 2020-04-13 22:44, Mathieu Poirier wrote:
On Mon, Apr 13, 2020 at 01:55:30PM +0530, Sai Prakash Ranjan wrote:
Hi Suzuki,
On 2020-04-13 04:47, Suzuki K Poulose wrote:
> Hi Sai,
>
> On 04/09/2020 12:35 PM, Sai Prakash Ranjan wrote:
> > Reading TMC mode register in tmc_read_prepare_etb without
> > enabling the TMC hardware leads to async exceptions like
> > the one in the call trace below. This can happen if the
> > user tries to read the TMC etf data via device node without
> > setting up source and the sink first which enables the TMC
> > hardware in the path. So make sure that the TMC is enabled
> > before we try to read TMC data.
>
> So, one can trigger the same SError by simply :
>
> $ cat /sys/bus/coresight/device/tmc_etb0/mgmt/mode
>
I do not see any SError when I run the above command.
localhost ~ # cat /sys/bus/coresight/devices/tmc_etf0/mgmt/mode
0x0
And this is most likely due to
commit cd9e3474bb793dc ("coresight: add PM runtime calls to
coresight_simple_func()")
Ok, so this is related to power management (you can ignore my question
in the
previous email).
Regarding function tmc_read_prepare_etb(), the best way to deal with
this is
probably make sure drvdata->mode != CS_MODE_DISABLED before reading
TMC_MODE.
If there is a buffer to read it will have been copied when the ETB was
disabled
and there won't be a need to access the HW.
This works as well, thanks.
diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c
b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index d0cc3985b72a..7ffe05930984 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -596,6 +596,11 @@ int tmc_read_prepare_etb(struct tmc_drvdata
*drvdata)
goto out;
}
+ if (drvdata->mode == CS_MODE_DISABLED) {
+ ret = -EINVAL;
+ goto out;
+ }
+
/* There is no point in reading a TMC in HW FIFO mode */
mode = readl_relaxed(drvdata->base + TMC_MODE);
if (mode != TMC_MODE_CIRCULAR_BUFFER) {
Thanks,
Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member
of Code Aurora Forum, hosted by The Linux Foundation
