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    SubjectRe: [PATCH 05/10] coresight: trbe: Allow driver to choose a different alignment
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    On 7/28/21 7:22 PM, Suzuki K Poulose wrote:
    > The TRBE hardware mandates a minimum alignment for the TRBPTR_EL1,
    > advertised via the TRBIDR_EL1. This is used by the driver to
    > align the buffer write head. This patch allows the driver to
    > choose a different alignment from that of the hardware, by
    > decoupling the alignment tracking. This will be useful for
    > working around errata.
    >
    > Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    > Cc: Anshuman Khandual <anshuman.khandual@arm.com>
    > Cc: Mike Leach <mike.leach@linaro.org>
    > Cc: Leo Yan <leo.yan@linaro.org>
    > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    > ---
    > drivers/hwtracing/coresight/coresight-trbe.c | 12 ++++++++----
    > 1 file changed, 8 insertions(+), 4 deletions(-)
    >
    > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
    > index 9735d514c5e1..9ea28813182b 100644
    > --- a/drivers/hwtracing/coresight/coresight-trbe.c
    > +++ b/drivers/hwtracing/coresight/coresight-trbe.c
    > @@ -92,7 +92,8 @@ static unsigned long trbe_errata_cpucaps[TRBE_ERRATA_MAX] = {
    > /*
    > * struct trbe_cpudata: TRBE instance specific data
    > * @trbe_flag - TRBE dirty/access flag support
    > - * @tbre_align - Actual TRBE alignment required for TRBPTR_EL1.
    > + * @trbe_hw_align - Actual TRBE alignment required for TRBPTR_EL1.
    > + * @trbe_align - Software alignment used for the TRBPTR_EL1,
    > * @cpu - CPU this TRBE belongs to.
    > * @mode - Mode of current operation. (perf/disabled)
    > * @drvdata - TRBE specific drvdata
    > @@ -100,6 +101,7 @@ static unsigned long trbe_errata_cpucaps[TRBE_ERRATA_MAX] = {
    > */
    > struct trbe_cpudata {
    > bool trbe_flag;
    > + u64 trbe_hw_align;
    > u64 trbe_align;
    > int cpu;
    > enum cs_mode mode;
    > @@ -906,7 +908,7 @@ static ssize_t align_show(struct device *dev, struct device_attribute *attr, cha
    > {
    > struct trbe_cpudata *cpudata = dev_get_drvdata(dev);
    >
    > - return sprintf(buf, "%llx\n", cpudata->trbe_align);
    > + return sprintf(buf, "%llx\n", cpudata->trbe_hw_align);
    > }
    > static DEVICE_ATTR_RO(align);
    >
    > @@ -995,11 +997,13 @@ static void arm_trbe_probe_cpu(void *info)
    > }
    >
    > trbe_check_errata(cpudata);
    > - cpudata->trbe_align = 1ULL << get_trbe_address_align(trbidr);
    > - if (cpudata->trbe_align > SZ_2K) {
    > +
    > + cpudata->trbe_hw_align = 1ULL << get_trbe_address_align(trbidr);
    > + if (cpudata->trbe_hw_align > SZ_2K) {
    > pr_err("Unsupported alignment on cpu %d\n", cpu);
    > goto cpu_clear;
    > }
    > + cpudata->trbe_align = cpudata->trbe_hw_align;

    When it changes, it must be asserted that trbe_align would be a multiple
    of trbe_hw_align before existing from arm_trbe_probe_cpu().

    > cpudata->trbe_flag = get_trbe_flag_update(trbidr);
    > cpudata->cpu = cpu;
    > cpudata->drvdata = drvdata;
    >

    Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>

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