linux-kernel - Re: [PATCH v5] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM

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Message-ID: <0e56f56e-157e-ecf2-bb21-74b79ffdf2ac@huawei.com>
Date:   Mon, 7 Dec 2020 19:21:30 +0800
From:   Qi Liu <liuqi115@...wei.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     <mike.leach@...aro.org>, <coresight@...ts.linaro.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linuxarm@...wei.com>
Subject: Re: [PATCH v5] coresight: etm4x: Modify core-commit of cpu to avoid
 the overflow of HiSilicon ETM


Hi Suzuki,
On 2020/12/7 18:38, Suzuki K Poulose wrote:
> On 12/7/20 2:08 AM, Qi Liu wrote:
>> Hi Mathieu,
>>
>> On 2020/12/5 2:55, Mathieu Poirier wrote:
>>> On Thu, Nov 26, 2020 at 09:34:30PM +0800, Qi Liu wrote:
>>>> The ETM device can't keep up with the core pipeline when cpu core
>>>> is at full speed. This may cause overflow within core and its ETM.
>>>> This is a common phenomenon on ETM devices.
>>>>
>>>> On HiSilicon Hip08 platform, a specific feature is added to set
>>>> core pipeline. So commit rate can be reduced manually to avoid ETM
>>>> overflow.
>>>>
>>>> Signed-off-by: Qi Liu <liuqi115@...wei.com>
>>>> ---
>>>> Change since v1:
>>>> - add CONFIG_ETM4X_IMPDEF_FEATURE and CONFIG_ETM4X_IMPDEF_HISILICON
>>>>    to keep specific feature off platforms which don't use it.
>>>> Change since v2:
>>>> - remove some unused variable.
>>>> Change since v3:
>>>> - use read/write_sysreg_s() to access register.
>>>> Change since v4:
>>>> - rename the call back function to a more generic name, and fix some
>>>>    compile warnings.
>>>>
>>>>   drivers/hwtracing/coresight/Kconfig                |  9 +++
>>>>   drivers/hwtracing/coresight/coresight-etm4x-core.c | 88 ++++++++++++++++++++++
>>>>   drivers/hwtracing/coresight/coresight-etm4x.h      |  8 ++
>>>>   3 files changed, 105 insertions(+)
>>>>
>>>> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
>>>> index c119824..1cc3601 100644
>>>> --- a/drivers/hwtracing/coresight/Kconfig
>>>> +++ b/drivers/hwtracing/coresight/Kconfig
>>>> @@ -110,6 +110,15 @@ config CORESIGHT_SOURCE_ETM4X
>>>>         To compile this driver as a module, choose M here: the
>>>>         module will be called coresight-etm4x.
>>>>
>>>> +config ETM4X_IMPDEF_FEATURE
>>>> +    bool "Control overflow impdef support in CoreSight ETM 4.x driver "
>>>> +    depends on CORESIGHT_SOURCE_ETM4X
>>>> +    help
>>>> +      This control provides overflow implement define for CoreSight
>>>> +      ETM 4.x tracer module which could not reduce commit race
>>>> +      automatically, and could avoid overflow within ETM tracer module
>>>> +      and its cpu core.
>>>> +
>>>>   config CORESIGHT_STM
>>>>       tristate "CoreSight System Trace Macrocell driver"
>>>>       depends on (ARM && !(CPU_32v3 || CPU_32v4 || CPU_32v4T)) || ARM64
>>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>>>> index abd706b..fcee27a 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
>>>> @@ -3,6 +3,7 @@
>>>>    * Copyright (c) 2014, The Linux Foundation. All rights reserved.
>>>>    */
>>>>
>>>> +#include <linux/bitops.h>
>>>>   #include <linux/kernel.h>
>>>>   #include <linux/moduleparam.h>
>>>>   #include <linux/init.h>
>>>> @@ -28,7 +29,9 @@
>>>>   #include <linux/perf_event.h>
>>>>   #include <linux/pm_runtime.h>
>>>>   #include <linux/property.h>
>>>> +
>>>>   #include <asm/sections.h>
>>>> +#include <asm/sysreg.h>
>>>>   #include <asm/local.h>
>>>>   #include <asm/virt.h>
>>>>
>>>> @@ -103,6 +106,87 @@ struct etm4_enable_arg {
>>>>       int rc;
>>>>   };
>>>>
>>>> +#ifdef CONFIG_ETM4X_IMPDEF_FEATURE
>>>> +
>>>> +#define HISI_HIP08_AMBA_ID        0x000b6d01
>>>> +#define ETM4_AMBA_MASK            0xfffff
>>>> +#define HISI_HIP08_CORE_COMMIT_CLEAR    0x3000
>>>
>>> Here bit 12 and 13 are cleared but in etm4_hisi_config_core_commit() only bit 12
>>> is set - is this intentional?  What is bit 13 for?
>>>
>> bit 12 and 13 are used together to set core-commit, 2'b00 means cpu is at full speed,
>> 2'b01, 2'b10, 2'b11 means reduce the speed of cpu pipeline, and 2'b01 means speed is
>> reduced to minimum value. So bit 12 and 13 should be cleared together in
>> etm4_hisi_config_core_commit().
> 
> Please could you document this in the function.
> 
of course, thanks.
>>
>> Qi
>>
>>>> +#define HISI_HIP08_CORE_COMMIT_SHIFT    12
>>>> +#define HISI_HIP08_CORE_COMMIT_REG    sys_reg(3, 1, 15, 2, 5)
>>>> +
>>>> +struct etm4_arch_features {
>>>> +    void (*arch_callback)(bool enable);
>>>> +};
>>>> +
>>>> +static bool etm4_hisi_match_pid(unsigned int id)
>>>> +{
>>>> +    return (id & ETM4_AMBA_MASK) == HISI_HIP08_AMBA_ID;
>>>> +}
>>>> +
>>>> +static void etm4_hisi_config_core_commit(bool enable)
>>>> +{
>>>> +    u64 val;
>>>> +
>>>> +    val = read_sysreg_s(HISI_HIP08_CORE_COMMIT_REG);
>>>> +    val &= ~HISI_HIP08_CORE_COMMIT_CLEAR;
>>>> +    val |= enable << HISI_HIP08_CORE_COMMIT_SHIFT;
> 
> I would use the explicitly masked values when you update
> a register.
> 
ok, how about changing these code to this:
val &= ~GENMASK(12, 13);

Thanks
Qi

> With the above:
> 
> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> 
> .
>