[PATCH] coresight: Fix disabling of CoreSight TPIU

[Mathieu Poirier]

On 28 November 2017 at 01:55, Robert Walker <robert.walker at arm.com> wrote:
> Hi Mathieu,
>
>> -----Original Message-----
>> From: Mathieu Poirier [mailto:mathieu.poirier at linaro.org]
>> Sent: 27 November 2017 17:30
>> To: Robert Walker <Robert.Walker at arm.com>
>> Cc: linux-arm-kernel at lists.infradead.org; CoreSight at lists.linaro.org
>> Subject: Re: [PATCH] coresight: Fix disabling of CoreSight TPIU
>>
>> Hi Robert,
>>
>> On 24 November 2017 at 02:58, Robert Walker <robert.walker at arm.com>
>> wrote:
>> > The CoreSight TPIU should be disabled when tracing to other sinks to
>> > allow them to operate at full bandwidth.
>> >
>> > This patch fixes tpiu_disable_hw() to correctly disable the TPIU by
>> > configuring the TPIU to stop on flush, initiating a manual flush,
>> > waiting for the flush to complete and then waits for the TPIU to
>> > indicate it has stopped.
>> >
>> > Signed-off-by: Robert Walker <robert.walker at arm.com>
>> > ---
>> >  drivers/hwtracing/coresight/coresight-tpiu.c | 13 ++++++++++---
>> >  1 file changed, 10 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/drivers/hwtracing/coresight/coresight-tpiu.c
>> > b/drivers/hwtracing/coresight/coresight-tpiu.c
>> > index bef49a3..4b46c49 100644
>> > --- a/drivers/hwtracing/coresight/coresight-tpiu.c
>> > +++ b/drivers/hwtracing/coresight/coresight-tpiu.c
>> > @@ -46,8 +46,11 @@
>> >  #define TPIU_ITATBCTR0         0xef8
>> >
>> >  /** register definition **/
>> > +/* FFSR - 0x300 */
>> > +#define FFSR_FT_STOPPED                BIT(1)
>> >  /* FFCR - 0x304 */
>> >  #define FFCR_FON_MAN           BIT(6)
>> > +#define FFCR_STOP_FI           BIT(12)
>> >
>> >  /**
>> >   * @base:      memory mapped base address for this component.
>> > @@ -85,10 +88,14 @@ static void tpiu_disable_hw(struct tpiu_drvdata
>> > *drvdata)  {
>> >         CS_UNLOCK(drvdata->base);
>> >
>> > -       /* Clear formatter controle reg. */
>> > -       writel_relaxed(0x0, drvdata->base + TPIU_FFCR);
>> > +       /* Clear formatter and stop on flush */
>> > +       writel_relaxed(FFCR_STOP_FI, drvdata->base + TPIU_FFCR);
>> >         /* Generate manual flush */
>> > -       writel_relaxed(FFCR_FON_MAN, drvdata->base + TPIU_FFCR);
>> > +       writel_relaxed(FFCR_STOP_FI | FFCR_FON_MAN, drvdata->base +
>> TPIU_FFCR);
>> > +       /* Wait for flush to complete */
>> > +       coresight_timeout(drvdata->base, TPIU_FFCR, FFCR_FON_MAN, 0);
>> > +       /* Wait for formatter to stop */
>> > +       coresight_timeout(drvdata->base, TPIU_FFSR, FFSR_FT_STOPPED,
>> > + 1);
>> >
>> >         CS_LOCK(drvdata->base);
>> >  }
>>
>> Shouldn't we also do this at boot time when the TPIU in _probed() ?
>> That way the TPIU doesn't have to explicitly be enabled and disabled prior to
>> running other tracing sessions.
>>
>> Thanks,
>> Mathieu
>
> There already is a call to tpiu_disable_hw() in tpiu_probe(), so the TPIU is disabled on boot.

Nothing has happened on the TPIU side since I first re-worked the
driver, thanks for the reminder.


> When tracing to another sink (e.g. ETR), the TPIU won't be enabled / disabled (i.e. tpiu_enable_hw() and tpiu_disable_hw() won't be called) as it's not on the direct path from source to sink.

Right, that part is of no concern to me.

>
> Regards
>
> Rob
>
>>
>>
>> > --
>> > 1.9.1
>> >
>