linux-kernel - Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace

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Date:   Tue, 19 May 2020 12:51:25 -0600
From:   Rob Herring <robh@...nel.org>
To:     Joakim Zhang <qiangqing.zhang@....com>
Cc:     john.garry@...wei.com, will@...nel.org, mark.rutland@....com,
        shawnguo@...nel.org, linux-imx@....com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier
 for userspace

On Tue, May 12, 2020 at 03:31:13PM +0800, Joakim Zhang wrote:
> The DDR Perf for i.MX8 is a system PMU whose axi id would different from
> SoC to SoC. Need expose system PMU identifier for userspace which refer
> to /sys/bus/event_source/devices/<PMU DEVICE>/identifier.

Why not just expose the AXI ID if that's what's different?

> 
> Reviewed-by: John Garry <john.garry@...wei.com>
> Signed-off-by: Joakim Zhang <qiangqing.zhang@....com>
> ---
>  drivers/perf/fsl_imx8_ddr_perf.c | 45 +++++++++++++++++++++++++++++---
>  1 file changed, 42 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/perf/fsl_imx8_ddr_perf.c b/drivers/perf/fsl_imx8_ddr_perf.c
> index 95dca2cb5265..88addbffbbd0 100644
> --- a/drivers/perf/fsl_imx8_ddr_perf.c
> +++ b/drivers/perf/fsl_imx8_ddr_perf.c
> @@ -50,21 +50,38 @@ static DEFINE_IDA(ddr_ida);
>  
>  struct fsl_ddr_devtype_data {
>  	unsigned int quirks;    /* quirks needed for different DDR Perf core */
> +	const char *identifier;	/* system PMU identifier for userspace */
>  };
>  
> -static const struct fsl_ddr_devtype_data imx8_devtype_data;
> +static const struct fsl_ddr_devtype_data imx8_devtype_data = {
> +	.identifier = "i.MX8",
> +};
> +
> +static const struct fsl_ddr_devtype_data imx8mq_devtype_data = {
> +	.quirks = DDR_CAP_AXI_ID_FILTER,
> +	.identifier = "i.MX8MQ",
> +};
> +
> +static const struct fsl_ddr_devtype_data imx8mm_devtype_data = {
> +	.quirks = DDR_CAP_AXI_ID_FILTER,
> +	.identifier = "i.MX8MM",
> +};
>  
> -static const struct fsl_ddr_devtype_data imx8m_devtype_data = {
> +static const struct fsl_ddr_devtype_data imx8mn_devtype_data = {
>  	.quirks = DDR_CAP_AXI_ID_FILTER,
> +	.identifier = "i.MX8MN",
>  };
>  
>  static const struct fsl_ddr_devtype_data imx8mp_devtype_data = {
>  	.quirks = DDR_CAP_AXI_ID_FILTER_ENHANCED,
> +	.identifier = "i.MX8MP",
>  };
>  
>  static const struct of_device_id imx_ddr_pmu_dt_ids[] = {
>  	{ .compatible = "fsl,imx8-ddr-pmu", .data = &imx8_devtype_data},
> -	{ .compatible = "fsl,imx8m-ddr-pmu", .data = &imx8m_devtype_data},

You need to keep the old one for compatibility.

> +	{ .compatible = "fsl,imx8mq-ddr-pmu", .data = &imx8mq_devtype_data},
> +	{ .compatible = "fsl,imx8mm-ddr-pmu", .data = &imx8mm_devtype_data},
> +	{ .compatible = "fsl,imx8mn-ddr-pmu", .data = &imx8mn_devtype_data},
>  	{ .compatible = "fsl,imx8mp-ddr-pmu", .data = &imx8mp_devtype_data},
>  	{ /* sentinel */ }
>  };
> @@ -84,6 +101,27 @@ struct ddr_pmu {
>  	int id;
>  };
>  
> +static ssize_t ddr_perf_identifier_show(struct device *dev,
> +					struct device_attribute *attr,
> +					char *page)
> +{
> +	struct ddr_pmu *pmu = dev_get_drvdata(dev);
> +
> +	return sprintf(page, "%s\n", pmu->devtype_data->identifier);

Why do we need yet another way to identify the SoC from userspace?

> +}
> +
> +static struct device_attribute ddr_perf_identifier_attr =
> +	__ATTR(identifier, 0444, ddr_perf_identifier_show, NULL);

sysfs attributes are supposed to be documented.

> +
> +static struct attribute *ddr_perf_identifier_attrs[] = {
> +	&ddr_perf_identifier_attr.attr,
> +	NULL,
> +};
> +
> +static struct attribute_group ddr_perf_identifier_attr_group = {
> +	.attrs = ddr_perf_identifier_attrs,
> +};
> +
>  enum ddr_perf_filter_capabilities {
>  	PERF_CAP_AXI_ID_FILTER = 0,
>  	PERF_CAP_AXI_ID_FILTER_ENHANCED,
> @@ -237,6 +275,7 @@ static const struct attribute_group *attr_groups[] = {
>  	&ddr_perf_format_attr_group,
>  	&ddr_perf_cpumask_attr_group,
>  	&ddr_perf_filter_cap_attr_group,
> +	&ddr_perf_identifier_attr_group,
>  	NULL,
>  };
>  
> -- 
> 2.17.1
>