Re: [PATCH v4 20/25] coresight: etm4x: Detect system instructions support

From: Tingwei Zhang <tingweiz@codeaurora.org>
To: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: anshuman.khandual@arm.com, coresight@lists.linaro.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	jonathan.zhouwen@huawei.com, mike.leach@linaro.org
Subject: Re: [PATCH v4 20/25] coresight: etm4x: Detect system instructions support
Date: Tue, 24 Nov 2020 08:41:55 +0800	[thread overview]
Message-ID: <20201124004155.GA10220@codeaurora.org> (raw)
In-Reply-To: <1c8d4b13-0c80-0bd3-29a6-dd586841377f@arm.com>

On Mon, Nov 23, 2020 at 05:39:43PM +0800, Suzuki K Poulose wrote:
> On 11/23/20 7:58 AM, Tingwei Zhang wrote:
> >Hi Suzuki,
> >
> >On Fri, Nov 20, 2020 at 12:45:42AM +0800, Suzuki K Poulose wrote:
> >>ETM v4.4 onwards adds support for system instruction access
> >>to the ETM. Detect the support on an ETM and switch to using the
> >>mode when available.
> >>
> >>Cc: Mike Leach <mike.leach@linaro.org>
> >>Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> >>Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> >>---
> >>  .../coresight/coresight-etm4x-core.c          | 39 +++++++++++++++++++
> >>  1 file changed, 39 insertions(+)
> >>
> >>diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> >>b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> >>index 7ac0a185c146..5cbea9c27f58 100644
> >>--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> >>+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> >>@@ -684,6 +684,37 @@ static const struct coresight_ops etm4_cs_ops = {
> >>  	.source_ops	= &etm4_source_ops,
> >>  };
> >>
> >>+static inline bool cpu_supports_sysreg_trace(void)
> >>+{
> >>+	u64 dfr0 = read_sysreg_s(SYS_ID_AA64DFR0_EL1);
> >>+
> >>+	return ((dfr0 >> ID_AA64DFR0_TRACEVER_SHIFT) & 0xfUL) > 0;
> >>+}
> >>+
> >>+static bool etm4_init_sysreg_access(struct etmv4_drvdata *drvdata,
> >>+				    struct csdev_access *csa)
> >>+{
> >>+	u32 devarch;
> >>+
> >>+	if (!cpu_supports_sysreg_trace())
> >>+		return false;
> >>+
> >>+	/*
> >>+	 * ETMs implementing sysreg access must implement TRCDEVARCH.
> >>+	 */
> >>+	devarch = read_etm4x_sysreg_const_offset(TRCDEVARCH);
> >>+	if ((devarch & ETM_DEVARCH_ID_MASK) != ETM_DEVARCH_ETMv4x_ARCH)
> >
> >Is this driver suppose to work on ETM 5.0/ETE trace unit before ETE driver
> >is ready?
> 
> No, it is not supposed to work on an ETE without the ETE support. That check
> ensures that we only detect ETMv4x for now. The ETE driver support adds the
> ETE_ARCH as one of the supported ETMs. If you hack around it might still
> probe,
> but things could go terribly wrong if we access registers that are not
> available
> on ETE.
> 
> Btw, are you able to test this series on an ETMv4.4+ system ?
> 
I'm trying to test this series on an ETE. Look like it's not correct.
I'll apply ETE patch on top of this and test.

> Kind regards
> Suzuki
> _______________________________________________
> CoreSight mailing list
> CoreSight@lists.linaro.org
> https://lists.linaro.org/mailman/listinfo/coresight