linux-kernel - Re: [PATCH v4 2/3] soc: qcom: qcom_stats: Add QMP support for syncing ddr stats

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Message-ID: <6ldwvqqhk4lndesk7oac4ly2vhdxyd57f5hhijvutik5gm2czu@vmkasgeg2tmm>
Date: Wed, 28 May 2025 14:02:55 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Maulik Shah <maulik.shah@....qualcomm.com>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Doug Anderson <dianders@...omium.org>
Subject: Re: [PATCH v4 2/3] soc: qcom: qcom_stats: Add QMP support for
 syncing ddr stats

On Wed, May 28, 2025 at 02:51:32PM +0530, Maulik Shah wrote:
> Recent SoCs (SM8450 onwards) require QMP command to be sent before reading
> ddr stats. The duration field of ddr stats will get populated only if QMP
> command is sent.
> 
> Add support to send ddr stats freqsync QMP command.
> 
> Signed-off-by: Maulik Shah <maulik.shah@....qualcomm.com>
> ---
>  drivers/soc/qcom/qcom_stats.c | 34 +++++++++++++++++++++++++++++++++-
>  1 file changed, 33 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/soc/qcom/qcom_stats.c b/drivers/soc/qcom/qcom_stats.c
> index 33fd2a1574464768bd07289e743fbb79ba415e84..0545c8cbefb8f18758d4eb51638e4ecb94e05422 100644
> --- a/drivers/soc/qcom/qcom_stats.c
> +++ b/drivers/soc/qcom/qcom_stats.c
> @@ -13,6 +13,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/seq_file.h>
>  
> +#include <linux/soc/qcom/qcom_aoss.h>
>  #include <linux/soc/qcom/smem.h>
>  #include <clocksource/arm_arch_timer.h>
>  
> @@ -37,6 +38,8 @@
>  #define DDR_STATS_TYPE(data)		FIELD_GET(GENMASK(15, 8), data)
>  #define DDR_STATS_FREQ(data)		FIELD_GET(GENMASK(31, 16), data)
>  
> +static struct qmp *qcom_stats_qmp;
> +
>  struct subsystem_data {
>  	const char *name;
>  	u32 smem_item;
> @@ -188,12 +191,28 @@ static int qcom_ddr_stats_show(struct seq_file *s, void *d)
>  	struct ddr_stats_entry data[DDR_STATS_MAX_NUM_MODES];
>  	void __iomem *reg = (void __iomem *)s->private;
>  	u32 entry_count;
> -	int i;
> +	int i, ret;
>  
>  	entry_count = readl_relaxed(reg + DDR_STATS_NUM_MODES_ADDR);
>  	if (entry_count > DDR_STATS_MAX_NUM_MODES)
>  		return -EINVAL;
>  
> +	if (qcom_stats_qmp) {
> +		/*
> +		 * Recent SoCs (SM8450 onwards) do not have duration field
> +		 * populated from boot up onwards for both DDR LPM Stats
> +		 * and DDR Frequency Stats.
> +		 *
> +		 * Send QMP message to Always on processor which will
> +		 * populate duration field into MSG RAM area.
> +		 *
> +		 * Sent every time to read latest data.
> +		 */
> +		ret = qmp_send(qcom_stats_qmp, "{class: ddr, action: freqsync}");
> +		if (ret)
> +			return ret;
> +	}
> +
>  	reg += DDR_STATS_ENTRY_START_ADDR;
>  	memcpy_fromio(data, reg, sizeof(struct ddr_stats_entry) * entry_count);
>  
> @@ -304,6 +323,19 @@ static int qcom_stats_probe(struct platform_device *pdev)
>  
>  	for (i = 0; i < config->num_records; i++)
>  		d[i].appended_stats_avail = config->appended_stats_avail;
> +	/*
> +	 * QMP is used for DDR stats syncing to MSG RAM for recent SoCs (SM8450 onwards).
> +	 * The prior SoCs do not need QMP handle as the required stats are already present
> +	 * in MSG RAM, provided the DDR_STATS_MAGIC_KEY matches.
> +	 */
> +	qcom_stats_qmp = qmp_get(&pdev->dev);
> +	if (IS_ERR(qcom_stats_qmp)) {
> +		if (PTR_ERR(qcom_stats_qmp) == -EPROBE_DEFER)
> +			return -EPROBE_DEFER;
> +
> +		/* We assume any other error means it's not defined/needed */
> +		qcom_stats_qmp = NULL;

I still think that we shouldn't be ignoring actual errors here. I'd say,
check for of_property_present(dev->of_node, "qcom,qmp") before.

> +	}
>  
>  	root = debugfs_create_dir("qcom_stats", NULL);
>  
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry