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    SubjectRe: [PATCH 2/3] coresight: Fail to open with return stacks if they are unavailable
    Hi James,

    On Thu, Dec 09, 2021 at 11:13:55AM +0000, James Clark wrote:
    >
    >
    > On 09/12/2021 11:00, Suzuki K Poulose wrote:
    > > On 08/12/2021 16:09, James Clark wrote:
    > >> Maintain consistency with the other options by failing to open when they
    > >> aren't supported. For example ETM_OPT_TS, ETM_OPT_CTXTID2 and the newly
    > >> added ETM_OPT_BRANCH_BROADCAST all return with -EINVAL if they are
    > >> requested but not supported by hardware.
    > >>
    > >> The consequence of not doing this is that the user may not be
    > >> aware that they are not enabling the feature as it is silently disabled.
    > >>
    > >> Signed-off-by: James Clark <james.clark@arm.com>
    > >> ---
    > >>   drivers/hwtracing/coresight/coresight-etm4x-core.c | 13 +++++++++----
    > >>   1 file changed, 9 insertions(+), 4 deletions(-)
    > >>
    > >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
    > >> index d2bafb50c66a..0a9bb943a5e5 100644
    > >> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
    > >> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
    > >> @@ -674,10 +674,15 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
    > >>       }
    > >>         /* return stack - enable if selected and supported */
    > >> -    if ((attr->config & BIT(ETM_OPT_RETSTK)) && drvdata->retstack)
    > >> -        /* bit[12], Return stack enable bit */
    > >> -        config->cfg |= BIT(12);
    > >> -
    > >> +    if (attr->config & BIT(ETM_OPT_RETSTK)) {
    > >> +        if (!drvdata->retstack) {
    > >> +            ret = -EINVAL;
    > >> +            goto out;
    > >> +        } else {
    > >> +            /* bit[12], Return stack enable bit */
    > >> +            config->cfg |= BIT(12);
    > >> +        }
    > >
    > > nit: While at this, please could you change the hard coded value
    > > to ETM4_CFG_BIT_RETSTK ?
    > >
    > I started changing them all because I had trouble searching for bits by name but then
    > I thought it would snowball into a bigger change so I undid it.
    >
    > I think I'll just go and do it now if it's an issue here.

    I can apply this set right away and you send another patch to fix all hard coded
    bitfields or you can send another revision with all 4 patches included in it
    (bitfields fix plus these 3). Just let me know what you want to do. And next
    time please add a cover letter.

    Thanks,
    Mathieu

    >
    > > Otherwise, looks good to me
    > >
    > > Suzuki

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