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CC: <will@kernel.org>, <jonathan.cameron@huawei.com>,
	<yangyicong@hisilicon.com>, <linux-kernel@vger.kernel.org>,
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	<prime.zeng@hisilicon.com>
Subject: Re: [PATCH v2] drivers/perf: hisi: Enable HiSilicon Erratum 162700402
 quirk for HIP09
To: Junhao He <hejunhao3@huawei.com>
References: <20240227125231.53127-1-hejunhao3@huawei.com>
From: Yicong Yang <yangyicong@huawei.com>
Message-ID: <4d628dcb-e54f-a6da-83aa-822957674819@huawei.com>
Date: Thu, 29 Feb 2024 19:12:28 +0800
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On 2024/2/27 20:52, Junhao He wrote:
> HiSilicon UC PMU v2 suffers the erratum 162700402 that the PMU counter
> cannot be set due to the lack of clock under power saving mode. This will
> lead to error or inaccurate counts. The clock can be enabled by the PMU
> global enabling control.
> 
> This patch tries to fix this by set the UC PMU enable before set event
> period to turn on the clock, and then restore the UC PMU configuration.
> The counter register can hold its value without a clock.
> 
> Signed-off-by: Junhao He <hejunhao3@huawei.com>
> ---
> 
> Changes since V1:
> - Updated the comment regarding the quirk function.
> - Extract write counter normal to a helper function.
> Link: https://lore.kernel.org/all/20240207094245.34195-1-hejunhao3@huawei.com/
> 

This version looks clearer to me,

Reviewed-by: Yicong Yang <yangyicong@hisilicon.com>

>  drivers/perf/hisilicon/hisi_uncore_uc_pmu.c | 42 ++++++++++++++++++++-
>  1 file changed, 41 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/perf/hisilicon/hisi_uncore_uc_pmu.c b/drivers/perf/hisilicon/hisi_uncore_uc_pmu.c
> index 636fb79647c8..481dcc9e8fbf 100644
> --- a/drivers/perf/hisilicon/hisi_uncore_uc_pmu.c
> +++ b/drivers/perf/hisilicon/hisi_uncore_uc_pmu.c
> @@ -287,12 +287,52 @@ static u64 hisi_uc_pmu_read_counter(struct hisi_pmu *uc_pmu,
>  	return readq(uc_pmu->base + HISI_UC_CNTR_REGn(hwc->idx));
>  }
>  
> -static void hisi_uc_pmu_write_counter(struct hisi_pmu *uc_pmu,
> +static bool hisi_uc_pmu_get_glb_en_state(struct hisi_pmu *uc_pmu)
> +{
> +	u32 val;
> +
> +	val = readl(uc_pmu->base + HISI_UC_EVENT_CTRL_REG);
> +	return !!FIELD_GET(HISI_UC_EVENT_GLB_EN, val);
> +}
> +
> +static void hisi_uc_pmu_write_counter_normal(struct hisi_pmu *uc_pmu,
>  				      struct hw_perf_event *hwc, u64 val)
>  {
>  	writeq(val, uc_pmu->base + HISI_UC_CNTR_REGn(hwc->idx));
>  }
>  
> +static void hisi_uc_pmu_write_counter_quirk_v2(struct hisi_pmu *uc_pmu,
> +				      struct hw_perf_event *hwc, u64 val)
> +{
> +	hisi_uc_pmu_start_counters(uc_pmu);
> +	hisi_uc_pmu_write_counter_normal(uc_pmu, hwc, val);
> +	hisi_uc_pmu_stop_counters(uc_pmu);
> +}
> +
> +static void hisi_uc_pmu_write_counter(struct hisi_pmu *uc_pmu,
> +				      struct hw_perf_event *hwc, u64 val)
> +{
> +	bool enable = hisi_uc_pmu_get_glb_en_state(uc_pmu);
> +	bool erratum = uc_pmu->identifier == HISI_PMU_V2;
> +
> +	/*
> +	 * HiSilicon UC PMU v2 suffers the erratum 162700402 that the
> +	 * PMU counter cannot be set due to the lack of clock under power
> +	 * saving mode. This will lead to error or inaccurate counts.
> +	 * The clock can be enabled by the PMU global enabling control.
> +	 * The irq handler and pmu_start() will call the function to set
> +	 * period. If the function under irq context, the PMU has been
> +	 * enabled therefore we set counter directly. Other situations
> +	 * the PMU is disabled, we need to enable it to turn on the
> +	 * counter clock to set period, and then restore PMU enable
> +	 * status, the counter can hold its value without a clock.
> +	 */
> +	if (enable || !erratum)
> +		hisi_uc_pmu_write_counter_normal(uc_pmu, hwc, val);
> +	else
> +		hisi_uc_pmu_write_counter_quirk_v2(uc_pmu, hwc, val);
> +}
> +
>  static void hisi_uc_pmu_enable_counter_int(struct hisi_pmu *uc_pmu,
>  					   struct hw_perf_event *hwc)
>  {
>