RE: [EXT] Re: [PATCH v6 6/7] coresight: tmc: Stop trace capture on FlIn

[Linu Cherian]

Hi Mike,

> -----Original Message-----
> From: Mike Leach <mike.leach@xxxxxxxxxx>
> Sent: Friday, January 5, 2024 9:41 PM
> To: Linu Cherian <lcherian@xxxxxxxxxxx>
> Cc: suzuki.poulose@xxxxxxx; james.clark@xxxxxxx; leo.yan@xxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; coresight@xxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> krzysztof.kozlowski+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Sunil Kovvuri Goutham
> <sgoutham@xxxxxxxxxxx>; George Cherian <gcherian@xxxxxxxxxxx>
> Subject: [EXT] Re: [PATCH v6 6/7] coresight: tmc: Stop trace capture on FlIn
> 
> External Email
> 
> ----------------------------------------------------------------------
> Hi,
> 
> On Fri, 5 Jan 2024 at 05:59, Linu Cherian <lcherian@xxxxxxxxxxx> wrote:
> >
> > Configure TMC ETR and ETF to flush and stop trace capture on FlIn
> > event. As a side effect, do manual flush only if auto flush fails.
> >
> > Signed-off-by: Linu Cherian <lcherian@xxxxxxxxxxx>
> > ---
> > Changelog from v5:
> > * No changes
> >
> >  drivers/hwtracing/coresight/coresight-tmc-etf.c | 10 ++++++++--
> > drivers/hwtracing/coresight/coresight-tmc-etr.c | 10 ++++++++--
> >  drivers/hwtracing/coresight/coresight-tmc.h     |  3 +++
> >  3 files changed, 19 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > index 72c2315f4e23..57a9a9300d36 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> > @@ -34,7 +34,7 @@ static int __tmc_etb_enable_hw(struct tmc_drvdata
> *drvdata)
> >         writel_relaxed(TMC_MODE_CIRCULAR_BUFFER, drvdata->base +
> TMC_MODE);
> >         writel_relaxed(TMC_FFCR_EN_FMT | TMC_FFCR_EN_TI |
> >                        TMC_FFCR_FON_FLIN | TMC_FFCR_FON_TRIG_EVT |
> > -                      TMC_FFCR_TRIGON_TRIGIN,
> > +                      TMC_FFCR_TRIGON_TRIGIN |
> > + TMC_FFCR_STOP_ON_FLUSH,
> >                        drvdata->base + TMC_FFCR);
> >
> 
> This is a problem. Setting TMC_FFCR_STOP_ON_FLUSH changes the
> fundamentals of trigger event handling. Without this bit ETM can generate
> multiple event  + triggers which are then embedded into the formatted trace
> stream for later search.
> With this new bit the capture will stop on the first event. Setting this bit should
> be dependent on the mode being set to ETR_MODE_RESRV
> 
> 
> 

Okay, will add a configuration dependency here. 


> >         writel_relaxed(drvdata->trigger_cntr, drvdata->base +
> > TMC_TRG); @@ -615,7 +615,13 @@ static int tmc_panic_sync_etf(struct
> coresight_device *csdev)
> >         if (val != TMC_MODE_CIRCULAR_BUFFER)
> >                 goto out;
> >
> > -       tmc_flush_and_stop(drvdata);
> > +       val = readl(drvdata->base + TMC_FFSR);
> > +       /* Do manual flush and stop only if its not auto-stopped */
> > +       if (!(val & TMC_FFSR_FT_STOPPED)) {
> > +               dev_info(&csdev->dev,
> > +                        "%s: Triggering manual flush\n", __func__);
> > +               tmc_flush_and_stop(drvdata);
> > +       }
> >
> Is there some reason to believe that the stop on flush will not work?
> 

CTI misconfiguration or even skipping the CTI configuration could be the reasons.

> Using this conditional skips the  tmc_wait_for_tmcready() called by
> tmc_flush_and_stop() if the formatter is stopped - which is a different
> condition test on a different register.
> 

Okay got it. While add a tmc_wait_for_tmcready() for the event based flush as well.

> Why is this block of code not in the patch that introduces the
> tmc_panic_sync_etf()

Ack. Will merge the above block of code alone to the patch that introduces tmc_panic_sync_xxx

> 
> >         /* Sync registers from hardware to metadata region */
> >         mdata->sts = csdev_access_relaxed_read32(csa, TMC_STS); diff
> > --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > index ab7521bbb2f5..4b3c7ec7f62b 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > @@ -1113,7 +1113,7 @@ static int __tmc_etr_enable_hw(struct
> > tmc_drvdata *drvdata)
> >
> >         writel_relaxed(TMC_FFCR_EN_FMT | TMC_FFCR_EN_TI |
> >                        TMC_FFCR_FON_FLIN | TMC_FFCR_FON_TRIG_EVT |
> > -                      TMC_FFCR_TRIGON_TRIGIN,
> > +                      TMC_FFCR_TRIGON_TRIGIN |
> > + TMC_FFCR_STOP_ON_FLUSH,
> >                        drvdata->base + TMC_FFCR);
> >         writel_relaxed(drvdata->trigger_cntr, drvdata->base + TMC_TRG);
> >         tmc_enable_hw(drvdata);
> > @@ -1846,7 +1846,13 @@ static int tmc_panic_sync_etr(struct
> coresight_device *csdev)
> >         if (!(val & TMC_CTL_CAPT_EN))
> >                 goto out;
> >
> > -       tmc_flush_and_stop(drvdata);
> > +       val = readl(drvdata->base + TMC_FFSR);
> > +       /* Do manual flush and stop only if its not auto-stopped */
> > +       if (!(val & TMC_FFSR_FT_STOPPED)) {
> > +               dev_info(&csdev->dev,
> > +                        "%s: Triggering manual flush\n", __func__);
> > +               tmc_flush_and_stop(drvdata);
> > +       }
> >
> 
> Above comments for etf apply equally to etr.

Ack.

Linu Cherian