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

[Jonathan Zhou <jonathan.zhouwen@huawei.com>]

Hi Will
Thanks for your review and thanks for adding Mathieu.

On 08/09/2020 05:00, Will Deacon wrote:
> [+ Mathieu, since he maintains the driver you're changing]
> 
> On Mon, Aug 31, 2020 at 04:02:46PM +0800, 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)
> 
> Do we also need to make sure we initialise TRFCR_EL2 correctly for the host?
> 
As Suziki said in the previous patch[1], accessing TRFCR_EL1 under EL2
will be routed to TRFCR_EL2. I just did a default config in this patch.
Actually, it should be better if we can do this based on the trace
sessions or the kernel config.

[1] https://www.spinics.net/lists/arm-kernel/msg818953.html

Regards
Jonathan

> Will
> 
> (keeping rest of the patch intact for Mathieu)
> 
>> 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. */
>> +	if (trace_filt == 0x1) {
>> +		sys_trfcr_el1 = read_sysreg_s(SYS_TRFCR_EL1);
>> +		write_sysreg_s(sys_trfcr_el1 | SYS_TRFCR_EL1_E0TRE,
>> +				SYS_TRFCR_EL1);
>> +		isb();
>> +	}
>> +}
>> +
>>  static void etm4_set_default_config(struct etmv4_config *config)
>>  {
>>  	/* disable all events tracing */
>> @@ -1504,6 +1523,10 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
>>  				etm4_init_arch_data,  drvdata, 1))
>>  		dev_err(dev, "ETM arch init failed\n");
>>  
>> +	if (smp_call_function_single(drvdata->cpu,
>> +				etm4_init_sysctrl, drvdata, 1))
>> +		dev_err(dev, "ETM sysctrl init failed\n");
>> +
>>  	ret = etm4_pm_setup_cpuslocked();
>>  	cpus_read_unlock();
>>  
>> -- 
>> 1.9.1
>>
> .
> 


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