Re: [PATCH v2] Coresight: etm4x: add support for Self-hosted trace

[Suzuki K Poulose <suzuki.poulose@arm.com>]

On 08/31/2020 09:02 AM, Jonathan Zhou wrote:
> ARMv8.4 architecture extension introduces ARMv8.4-Trace, Armv8.4
> Self-hosted Trace Extensions. It provides control of exception
> levels and security states. Let's add this feature detection and
> enable E1TRE and E0TRE in TRFCR_EL1 if Self-hosted Trace is
> supported.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
> Signed-off-by: Jonathan Zhou <jonathan.zhouwen@huawei.com>
> ---
>   arch/arm64/include/asm/sysreg.h               |  8 ++++++++
>   drivers/hwtracing/coresight/coresight-etm4x.c | 23 +++++++++++++++++++++++
>   2 files changed, 31 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index 554a7e8ecb07..53da5f326667 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -184,6 +184,13 @@
>   
>   #define SYS_ZCR_EL1			sys_reg(3, 0, 1, 2, 0)
>   
> +/* Trace Filter control */
> +#define SYS_TRFCR_EL1			sys_reg(3, 0, 1, 2, 1)

> +/* Trace is allowed at EL0 */
> +#define SYS_TRFCR_EL1_E0TRE		BIT(0)
> +/* Trace is allowed at EL1 */
> +#define SYS_TRFCR_EL1_E1TRE		BIT(1)
> +

Please drop SYS suffix for the fields.

>   #define SYS_TTBR0_EL1			sys_reg(3, 0, 2, 0, 0)
>   #define SYS_TTBR1_EL1			sys_reg(3, 0, 2, 0, 1)
>   #define SYS_TCR_EL1			sys_reg(3, 0, 2, 0, 2)
> @@ -772,6 +779,7 @@
>   #define ID_AA64MMFR2_CNP_SHIFT		0
>   
>   /* id_aa64dfr0 */
> +#define ID_AA64DFR0_SELF_HOSTED_SHIFT	40
>   #define ID_AA64DFR0_DOUBLELOCK_SHIFT	36
>   #define ID_AA64DFR0_PMSVER_SHIFT	32
>   #define ID_AA64DFR0_CTX_CMPS_SHIFT	28
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 96425e818fc2..f72b457c2bad 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c
> @@ -28,6 +28,7 @@
>   #include <linux/perf_event.h>
>   #include <linux/pm_runtime.h>
>   #include <linux/property.h>
> +#include <asm/sysreg.h>
>   #include <asm/sections.h>
>   #include <asm/local.h>
>   #include <asm/virt.h>
> @@ -785,6 +786,24 @@ static void etm4_init_arch_data(void *info)
>   	CS_LOCK(drvdata->base);
>   }
>   
> +static void etm4_init_sysctrl(void *info)
> +{
> +	u64 sys_trfcr_el1, dfr0;
> +	int trace_filt;
> +
> +	dfr0 = read_sysreg(id_aa64dfr0_el1);
> +
> +	trace_filt = cpuid_feature_extract_unsigned_field(dfr0,
> +					ID_AA64DFR0_SELF_HOSTED_SHIFT);
> +	/* if selfhosted trace implemented, enable trace EL0 as default. */

What about EL1 ? We do support kernel tracing. I believe we need to do
this every time when we enable etm4, based on the selected config.


Suzuki

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