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

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Message-ID: <4f7168d9-8d8e-4fdf-8917-47c1cc71cf82@oss.qualcomm.com>
Date: Thu, 29 May 2025 21:07:49 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        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 5/28/25 1:02 PM, Dmitry Baryshkov wrote:
> 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.

/**
 * qmp_get() - get a qmp handle from a device
 * @dev: client device pointer
 *
 * Return: handle to qmp device on success, ERR_PTR() on failure
 */
struct qmp *qmp_get(struct device *dev)
{
        struct platform_device *pdev;
        struct device_node *np;
        struct qmp *qmp;

        if (!dev || !dev->of_node)
                return ERR_PTR(-EINVAL);

        np = of_parse_phandle(dev->of_node, "qcom,qmp", 0);
        if (!np)
                return ERR_PTR(-ENODEV);

        pdev = of_find_device_by_node(np);
        of_node_put(np);
        if (!pdev)
                return ERR_PTR(-EINVAL);

        qmp = platform_get_drvdata(pdev);

        if (!qmp) {
                put_device(&pdev->dev);
                return ERR_PTR(-EPROBE_DEFER);
        }
        return qmp;
}
EXPORT_SYMBOL_GPL(qmp_get);


Konrad