[PATCH] coresight: tmc: fix for trace collection bug in sysFS mode

On 14/09/16 12:30, Venkatesh Vivekanandan wrote:

On Wed, Sep 14, 2016 at 3:26 PM, Suzuki K Poulose <Suzuki.Poulose at arm.com <mailto:Suzuki.Poulose@arm.com>> wrote:

    On 13/09/16 16:41, Mathieu Poirier wrote:

        On 13 September 2016 at 06:20, Venkatesh Vivekanandan
        <venkatesh.vivekanandan at broadcom.com <mailto:venkatesh.vivekanandan@broadcom.com>> wrote:

            tmc_etb_dump_hw is never called in sysFS mode to collect trace from
            hardware, because drvdata->mode is set to CS_MODE_DISABLED at
            tmc_disable_etf/etr_sink

            static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
            {
                    .
                    .
                    if (local_read(&drvdata->mode) == CS_MODE_SYSFS)
                            tmc_etb_dump_hw(drvdata);
                    .
                    .
            }

            static void tmc_disable_etf_sink(struct coresight_device *csdev)
            {
                   .
                   .
                    val = local_xchg(&drvdata->mode, CS_MODE_DISABLED);
                    /* Disable the TMC only if it needs to */
                    if (val != CS_MODE_DISABLED)
                            tmc_etb_disable_hw(drvdata);


        You are correct.

                   .
                   .
            }

    I think we should :

    1) First switch the drvdata->mode to a normal type from local_t. Using an
    atomic type for mode is completely unnecessary and comes with the overhead
    of barriers/synchronisation instructions, while all accesses, including read/write
    are performed under the drvdata->spinlock. I have a patch already for this, which
    I plan to send it soon.

    and

    2) Do something like :

    void  tmc_disable_etX_sink()
    {
            if (drvdata->mode != CS_MODE_DISABLED) {
                    tmc_etX_disable_hw(drvdata);
                    drvdata->mode = CS_MODE_DISABLED;
            }
    }

You will fix this along with above changes?

Yes.

nit: Please fix your mail client. Do not use HTML formatted emails on mailing list

Cheers
Suzuki