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    SubjectRe: [PATCH v3 19/26] coresight: etm4x: Detect access early on the target CPU
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    On 11/6/20 8:34 PM, Mathieu Poirier wrote:
    > On Wed, Oct 28, 2020 at 10:09:38PM +0000, Suzuki K Poulose wrote:
    >> In preparation to detect the support for system instruction
    >> support, move the detection of the device access to the target
    >> CPU.
    >>
    >> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    >> ---
    >> .../coresight/coresight-etm4x-core.c | 45 ++++++++++++++++---
    >> 1 file changed, 40 insertions(+), 5 deletions(-)
    >>
    >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
    >> index f038bb10bc78..308674ab746c 100644
    >> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
    >> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
    >> @@ -56,6 +56,11 @@ static u64 etm4_get_access_type(struct etmv4_config *config);
    >>
    >> static enum cpuhp_state hp_online;
    >>
    >> +struct etm_init_arg {
    >
    > s/etm_init_arg/etm4_init_arg

    Part of the reason was to add a future IP support where it is not all
    ETM4. Again it doesn't really matter. I could change it.

    >
    >> + struct etmv4_drvdata *drvdata;
    >> + struct csdev_access *csa;
    >> +};
    >> +
    >> u64 etm4x_sysreg_read(struct csdev_access *csa,
    >> u32 offset,
    >> bool _relaxed,
    >> @@ -669,6 +674,22 @@ static const struct coresight_ops etm4_cs_ops = {
    >> .source_ops = &etm4_source_ops,
    >> };
    >>
    >> +static bool etm_init_iomem_access(struct etmv4_drvdata *drvdata,
    >> + struct csdev_access *csa)
    >> +{
    >> + *csa = CSDEV_ACCESS_IOMEM(drvdata->base);
    >> + return true;
    >> +}
    >> +
    >> +static bool etm_init_csdev_access(struct etmv4_drvdata *drvdata,
    >> + struct csdev_access *csa)
    >> +{
    >> + if (drvdata->base)
    >> + return etm_init_iomem_access(drvdata, csa);
    >> +
    >> + return false;
    >> +}
    >
    > Returning a boolean rather than an int for the above two functions seems odd to
    > me.
    >

    We don't return an error from the caller of these functions. So, all we
    need to know is, if the operation was success or failure. Having bool
    makes it explicit for the checkings, rather than documenting the
    expected return values. Hence the choice. But I am open to changing them
    if you prefer it that way.



    Cheers
    Suzuki

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