Re: [PATCH v5 18/19] coresight tmc: Add support for Coresight SoC 600 TMC

[Suzuki K Poulose]

On 24/07/17 18:12, Mathieu Poirier wrote:
> On 20 July 2017 at 04:17, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> > The coresight SoC 600 supports ETR save-restore which allows us
> > to restore a trace session by retaining the RRP/RWP/STS.Full values
> > when the TMC leaves the Disabled state. However, the TMC doesn't
> > have a scatter-gather unit in built.
> >
> > Also, TMCs have different PIDs in different configurations (ETF,
> > ETB & ETR), unlike the previous generation.
> >
> > While the DEVID exposes some of the features/changes in the TMC,
> > it doesn't explicitly advertises the new save-restore feature
> > as described above.
> >
> > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >  drivers/hwtracing/coresight/coresight-tmc.c | 16 ++++++++++++++++
> >  drivers/hwtracing/coresight/coresight-tmc.h |  4 ++++
> >  2 files changed, 20 insertions(+)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-tmc.c b/drivers/hwtracing/coresight/coresight-tmc.c
> > index c4a5dea..e754a3e 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc.c
> > @@ -442,6 +442,22 @@ static struct amba_id tmc_ids[] = {
> >                 .id     = 0x000bb961,
> >                 .mask   = 0x000fffff,
> >         },
> > +       {
> > +               /* Coresight SoC 600 TMC-ETR/ETS */
> > +               .id     = 0x000bb9e8,
> > +               .mask   = 0x000fffff,
> > +               .data   = (void *)(unsigned long)CORESIGHT_SOC_600_ETR_CAPS,
>
> It the casting to unsigned long mandatory?

Yes. Given the ETR caps is u32, we don't want a trouble with
little/big endian switch. Also, it keeps the compiler happy when you
upsize an integer to a pointer directly.

e.g:

$ cat cast.c
int main(void)
{
	void *ptr;
	int a;
	ptr = (void *)a;
	return 0;
}

Compiler warns:

cc     cast.c   -o cast
cast.c: In function âmainâ:
cast.c:5:8: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  ptr = (void *)a;
        ^

Cheers
Suzuki