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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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