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Message-ID: <03220d4a-281e-20b5-0962-3831ce3a8ec1@arm.com>
Date: Wed, 5 Jan 2022 18:09:15 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
linux-arm-kernel@...ts.infradead.org
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
coresight@...ts.linaro.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] coresight: trbe: Workaround TRBE trace data
corruption
On 1/5/22 5:29 PM, Suzuki K Poulose wrote:
> On 05/01/2022 05:05, Anshuman Khandual wrote:
>> TRBE implementations affected by Arm erratum #1902691 might corrupt trace
>> data or deadlock, when it's being written into the memory. Workaround this
>> problem in the driver, by preventing TRBE initialization on affected cpus.
>> This adds a new cpu errata in arm64 errata framework and also updates TRBE
>> driver as required.
>>
>> Cc: Catalin Marinas <catalin.marinas@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>> Cc: Suzuki Poulose <suzuki.poulose@....com>
>> Cc: coresight@...ts.linaro.org
>> Cc: linux-doc@...r.kernel.org
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>> Documentation/arm64/silicon-errata.rst | 2 ++
>> arch/arm64/Kconfig | 16 ++++++++++++++++
>> arch/arm64/kernel/cpu_errata.c | 9 +++++++++
>> arch/arm64/tools/cpucaps | 1 +
>> drivers/hwtracing/coresight/coresight-trbe.c | 12 ++++++++++++
>> 5 files changed, 40 insertions(+)
>>
>> diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
>> index e0ef3e9a4b8b..50018f60c4d4 100644
>> --- a/Documentation/arm64/silicon-errata.rst
>> +++ b/Documentation/arm64/silicon-errata.rst
>> @@ -56,6 +56,8 @@ stable kernels.
>> +----------------+-----------------+-----------------+-----------------------------+
>> | ARM | Cortex-A510 | #2038923 | ARM64_ERRATUM_2038923 |
>> +----------------+-----------------+-----------------+-----------------------------+
>> +| ARM | Cortex-A510 | #1902691 | ARM64_ERRATUM_1902691 |
>> ++----------------+-----------------+-----------------+-----------------------------+
>> | ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
>> +----------------+-----------------+-----------------+-----------------------------+
>> | ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 026e34fb6fad..1ea5c3b4aac0 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -819,6 +819,22 @@ config ARM64_ERRATUM_2038923
>> If unsure, say Y.
>> +config ARM64_ERRATUM_1902691
>> + bool "Cortex-A510: 1902691: workaround TRBE trace corruption"
>> + depends on CORESIGHT_TRBE
>> + default y
>> + help
>> + This option adds the workaround for ARM Cortex-A510 erratum 1902691.
>> +
>> + Affected Cortex-A510 core might cause trace data corruption, when being written
>> + into the memory. Effectively TRBE is broken and hence cannot be used to capture
>> + trace data.
>> +
>> + Work around this problem in the driver by just preventing TRBE initialization on
>> + affected cpus.
>> +
>> + If unsure, say Y.
>> +
>
> It might be better to add :
>
> "The firmware must have disabled the access to TRBE for the kernel on such implementations. This will cover the kernel for any firmware that
> doesn't do this already"
Right, will add it.
>
>
>> config CAVIUM_ERRATUM_22375
>> bool "Cavium erratum 22375, 24313"
>> default y
>> diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
>> index 60b0c1f1d912..a3336dfb5a8a 100644
>> --- a/arch/arm64/kernel/cpu_errata.c
>> +++ b/arch/arm64/kernel/cpu_errata.c
>> @@ -615,6 +615,15 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
>> /* Cortex-A510 r0p0 - r0p2 */
>> ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 2)
>> },
>> +#endif
>> +#ifdef CONFIG_ARM64_ERRATUM_1902691
>> + {
>> + .desc = "ARM erratum 1902691",
>> + .capability = ARM64_WORKAROUND_1902691,
>> +
>> + /* Cortex-A510 r0p0 - r0p1 */
>> + ERRATA_MIDR_REV_RANGE(MIDR_CORTEX_A510, 0, 0, 1)
>> + },
>> #endif
>> {
>> }
>> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
>> index 45a06d36d080..e7719e8f18de 100644
>> --- a/arch/arm64/tools/cpucaps
>> +++ b/arch/arm64/tools/cpucaps
>> @@ -57,6 +57,7 @@ WORKAROUND_1508412
>> WORKAROUND_1542419
>> WORKAROUND_2064142
>> WORKAROUND_2038923
>> +WORKAROUND_1902691
>> WORKAROUND_TRBE_OVERWRITE_FILL_MODE
>> WORKAROUND_TSB_FLUSH_FAILURE
>> WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
>> diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
>> index 0689c6dab96d..b9b4e34fac15 100644
>> --- a/drivers/hwtracing/coresight/coresight-trbe.c
>> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
>> @@ -93,12 +93,14 @@ struct trbe_buf {
>> #define TRBE_WORKAROUND_WRITE_OUT_OF_RANGE 1
>> #define TRBE_WORKAROUND_SYSREG_WRITE_FAILURE 2
>> #define TRBE_WORKAROUND_CORRUPTION_WITH_ENABLE 3
>> +#define TRBE_IS_BROKEN 4
>> static int trbe_errata_cpucaps[] = {
>> [TRBE_WORKAROUND_OVERWRITE_FILL_MODE] = ARM64_WORKAROUND_TRBE_OVERWRITE_FILL_MODE,
>> [TRBE_WORKAROUND_WRITE_OUT_OF_RANGE] = ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE,
>> [TRBE_WORKAROUND_SYSREG_WRITE_FAILURE] = ARM64_WORKAROUND_2064142,
>> [TRBE_WORKAROUND_CORRUPTION_WITH_ENABLE] = ARM64_WORKAROUND_2038923,
>> + [TRBE_IS_BROKEN] = ARM64_WORKAROUND_1902691,
>> -1, /* Sentinel, must be the last entry */
>> };
>> @@ -181,6 +183,11 @@ static inline bool trbe_may_corrupt_with_enable(struct trbe_cpudata *cpudata)
>> return trbe_has_erratum(cpudata, TRBE_WORKAROUND_CORRUPTION_WITH_ENABLE);
>> }
>> +static inline bool trbe_is_broken(struct trbe_cpudata *cpudata)
>> +{
>> + return trbe_has_erratum(cpudata, TRBE_IS_BROKEN);
>> +}
>> +
>> static int trbe_alloc_node(struct perf_event *event)
>> {
>> if (event->cpu == -1)
>> @@ -1291,6 +1298,11 @@ static void arm_trbe_probe_cpu(void *info)
>> */
>> trbe_check_errata(cpudata);
>> + if (trbe_is_broken(cpudata)) {
>> + pr_err("TRBE might corrupt the trace on cpu %d\n", cpu);
>
> It may be better to say:
>
> "Disabling TRBE on CPU%d due to erratum"
Mention the erratum #1902691 as well or not required ?
>
> Otherwise looks good to me.
>
> Suzuki
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