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

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Message-ID: <9f2895b8-0a02-44f7-baa6-2afc7e29c1d6@oss.qualcomm.com>
Date: Thu, 5 Jun 2025 16:35:05 +0530
From: "Maulik Shah (mkshah)" <maulik.shah@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Konrad Dybcio <konrad.dybcio@....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 5/31/2025 2:19 AM, Dmitry Baryshkov wrote:
> On Thu, May 29, 2025 at 09:07:49PM +0200, Konrad Dybcio wrote:
>> 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);
> 
> So, I'd say, we need to identify whether it is this caluse or another
> error. It should be enough to ignore ENODEV and return an error in all
> other cases.
> 

I will update in v5 to check of_property_present(dev->of_node, "qcom,qmp") and then
return error accordingly.

Thanks,
Maulik

>>
>>         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
>