linux-kernel - Re: [PATCH] coresight: Disable MMIO logging for coresight stm driver

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Message-ID: <1efe761e-964b-4b24-b1e3-dc33bf1749b7@arm.com>
Date: Wed, 30 Apr 2025 14:51:38 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Mao Jinlong <quic_jinlmao@...cinc.com>, Mike Leach
 <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] coresight: Disable MMIO logging for coresight stm driver

Hi,

On 30/04/2025 12:03, Mao Jinlong wrote:
> When read/write registers with readl_relaxed and writel_relaxed,
> log_read_mmio and log_write_mmio will be called. If mmio trace
> is enabled to STM, STM driver will write the register to send the
> trace and writel_relaxed will be called again. The circular call
> like callstack below will happen. Disable mmio logging for stm
> driver to avoid this issue.
> 

Thanks for the fix, looks good to me. However, I think the commit 
description is a bit cryptic. Could we say :

With MMIO logging enabled, the MMIO access are traced and could be
sent to an STM device. Thus, an STM driver MMIO access could create
circular call chain with MMIO logging. Disable it for STM driver.

Suzuki

> [] stm_source_write[stm_core]+0xc4
> [] stm_ftrace_write[stm_ftrace]+0x40
> [] trace_event_buffer_commit+0x238
> [] trace_event_raw_event_rwmmio_rw_template+0x8c
> [] log_post_write_mmio+0xb4
> [] writel_relaxed[coresight_stm]+0x80
> [] stm_generic_packet[coresight_stm]+0x1a8
> [] stm_data_write[stm_core]+0x78
> [] ost_write[stm_p_ost]+0xc8
> [] stm_source_write[stm_core]+0x7c
> [] stm_ftrace_write[stm_ftrace]+0x40
> [] trace_event_buffer_commit+0x238
> [] trace_event_raw_event_rwmmio_read+0x84
> [] log_read_mmio+0xac
> [] readl_relaxed[coresight_tmc]+0x50
> 
> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
> ---
>   drivers/hwtracing/coresight/Makefile | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index 4ba478211b31..f3158266f75e 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -22,6 +22,8 @@ condflags := \
>   	$(call cc-option, -Wstringop-truncation)
>   subdir-ccflags-y += $(condflags)
>   
> +CFLAGS_coresight-stm.o := -D__DISABLE_TRACE_MMIO__
> +
>   obj-$(CONFIG_CORESIGHT) += coresight.o
>   coresight-y := coresight-core.o  coresight-etm-perf.o coresight-platform.o \
>   		coresight-sysfs.o coresight-syscfg.o coresight-config.o \