linux-kernel - Re: [PATCH v3 2/2] soc: qcom: Introduce RPM master stats driver

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Message-ID: <20230417082003.GA2874@thinkpad>
Date:   Mon, 17 Apr 2023 13:50:03 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/2] soc: qcom: Introduce RPM master stats driver

On Mon, Apr 17, 2023 at 09:14:39AM +0200, Konrad Dybcio wrote:
> 
> 
> On 16.04.2023 16:20, Manivannan Sadhasivam wrote:
> > On Fri, Apr 14, 2023 at 01:37:18PM +0200, Konrad Dybcio wrote:
> >> Introduce a driver to query and expose detailed, per-subsystem (as opposed
> >> to the existing qcom_stats driver which exposes SoC-wide data) about low
> >> power mode states of a given RPM master. That includes the APSS (ARM),
> >> MPSS (modem) and other remote cores, depending on the platform
> >> configuration.
> >>
> >> This is a vastly cleaned up and restructured version of a similar
> >> driver found in msm-5.4.
> >>
> >> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> >> ---
> >>  drivers/soc/qcom/Kconfig            |  11 +++
> >>  drivers/soc/qcom/Makefile           |   1 +
> >>  drivers/soc/qcom/rpm_master_stats.c | 160 ++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 172 insertions(+)
> >>
> >> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> >> index a491718f8064..e597799e8121 100644
> >> --- a/drivers/soc/qcom/Kconfig
> >> +++ b/drivers/soc/qcom/Kconfig
> >> @@ -135,6 +135,17 @@ config QCOM_RMTFS_MEM
> >>  
> >>  	  Say y here if you intend to boot the modem remoteproc.
> >>  
> >> +config QCOM_RPM_MASTER_STATS
> >> +	tristate "Qualcomm RPM Master stats"
> >> +	depends on ARCH_QCOM || COMPILE_TEST
> >> +	help
> >> +	  The RPM Master sleep stats driver provides detailed per-subsystem
> >> +	  sleep/wake data, read from the RPM message RAM. It can be used to
> >> +	  assess whether all the low-power modes available are entered as
> >> +	  expected or to check which part of the SoC prevents it from sleeping.
> >> +
> >> +	  Say y here if you intend to debug or monitor platform sleep.
> >> +
> >>  config QCOM_RPMH
> >>  	tristate "Qualcomm RPM-Hardened (RPMH) Communication"
> >>  	depends on ARCH_QCOM || COMPILE_TEST
> >> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
> >> index 0f43a88b4894..7349371fdea1 100644
> >> --- a/drivers/soc/qcom/Makefile
> >> +++ b/drivers/soc/qcom/Makefile
> >> @@ -14,6 +14,7 @@ obj-$(CONFIG_QCOM_QMI_HELPERS)	+= qmi_helpers.o
> >>  qmi_helpers-y	+= qmi_encdec.o qmi_interface.o
> >>  obj-$(CONFIG_QCOM_RAMP_CTRL)	+= ramp_controller.o
> >>  obj-$(CONFIG_QCOM_RMTFS_MEM)	+= rmtfs_mem.o
> >> +obj-$(CONFIG_QCOM_RPM_MASTER_STATS)	+= rpm_master_stats.o
> >>  obj-$(CONFIG_QCOM_RPMH)		+= qcom_rpmh.o
> >>  qcom_rpmh-y			+= rpmh-rsc.o
> >>  qcom_rpmh-y			+= rpmh.o
> >> diff --git a/drivers/soc/qcom/rpm_master_stats.c b/drivers/soc/qcom/rpm_master_stats.c
> >> new file mode 100644
> >> index 000000000000..73080c92bf89
> >> --- /dev/null
> >> +++ b/drivers/soc/qcom/rpm_master_stats.c
> >> @@ -0,0 +1,160 @@
> >> +// SPDX-License-Identifier: GPL-2.0-only
> >> +/*
> >> + * Copyright (c) 2012-2020, The Linux Foundation. All rights reserved.
> >> + * Copyright (c) 2023, Linaro Limited
> >> + *
> >> + * This driver supports what is known as "Master Stats v2", which seems to be
> >> + * the only version which has ever shipped, all the way from 2013 to 2023.
> > 
> > It'd better to mention "Qualcomm downstream" in the somewhere above comment to
> > make it clear for users.
> Ack
> 
> > 
> >> + */
> >> +
> >> +#include <linux/debugfs.h>
> >> +#include <linux/io.h>
> >> +#include <linux/module.h>
> >> +#include <linux/of.h>
> >> +#include <linux/of_address.h>
> >> +#include <linux/platform_device.h>
> >> +
> >> +struct master_stats_data {
> >> +	void __iomem *base;
> >> +	const char *label;
> >> +};
> >> +
> >> +struct rpm_master_stats {
> >> +	uint32_t active_cores;
> >> +	uint32_t num_shutdowns;
> >> +	uint64_t shutdown_req;
> >> +	uint64_t wakeup_idx;
> >> +	uint64_t bringup_req;
> >> +	uint64_t bringup_ack;
> >> +	uint32_t wakeup_reason; /* 0 = "rude wakeup", 1 = scheduled wakeup */
> >> +	uint32_t last_sleep_trans_dur;
> >> +	uint32_t last_wake_trans_dur;
> >> +
> >> +	/* Per-subsystem (*not necessarily* SoC-wide) XO shutdown stats */
> >> +	uint32_t xo_count;
> >> +	uint64_t xo_last_enter;
> >> +	uint64_t last_exit;
> >> +	uint64_t xo_total_dur;
> > 
> > Why can't you use u64, u32?
> Brain derp!
> 
> > 
> > Also, sort these members as below:
> > 
> > u64
> > u32
> No, it's the way this data is structured in the
> memory and we copy it as a whole.
> 

Ok, in that case you'd need __packed.

> > 
> >> +};
> >> +

[...]

> >> +		/*
> >> +		 * Generally it's not advised to fail on debugfs errors, but this
> >> +		 * driver's only job is exposing data therein.
> >> +		 */
> >> +		dent = debugfs_create_file(d[i].label, 0444, root,
> >> +					   &d[i], &master_stats_fops);
> >> +		if (!dent) {
> > 
> > Don't check for NULL, instead use IS_ERR() if you really care about error
> > checking here.
> "This function will return a pointer to a dentry if
> it succeeds. This pointer must be passed to the
> debugfs_remove function when the file is to be removed
> (no automatic cleanup happens if your module is unloaded,
> you are responsible here.) If an error occurs, NULL will
> be returned."

This seems to be the old comment. Take a look at the updated one in mainline:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/debugfs/inode.c#n468

Greg changed the semantics of the debugfs APIs a while back but the kernel doc
was updated recently:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/debugfs/inode.c?id=d3002468cb5d5da11e22145c9af32facd5c34352

- Mani

> 
> > 
> >> +			debugfs_remove_recursive(root);
> >> +			return -EINVAL;
> >> +		}
> >> +	}
> >> +
> >> +	device_set_pm_not_required(dev);
> >> +
> >> +	return 0;
> >> +}
> >> +
> >> +static void master_stats_remove(struct platform_device *pdev)
> >> +{
> >> +	struct dentry *root = platform_get_drvdata(pdev);
> >> +
> >> +	debugfs_remove_recursive(root);
> >> +}
> >> +
> >> +static const struct of_device_id rpm_master_table[] = {
> >> +	{ .compatible = "qcom,rpm-master-stats" },
> >> +	{ },
> >> +};
> >> +
> >> +static struct platform_driver master_stats_driver = {
> >> +	.probe = master_stats_probe,
> >> +	.remove_new = master_stats_remove,
> >> +	.driver = {
> >> +		.name = "rpm_master_stats",
> >> +		.of_match_table = rpm_master_table,
> >> +	},
> >> +};
> >> +module_platform_driver(master_stats_driver);
> >> +
> >> +MODULE_DESCRIPTION("RPM Master Statistics driver");
> > 
> > Qualcomm RPM Master Statistics driver
> Ack
> 
> Konrad
> > 
> > - Mani
> > 
> >> +MODULE_LICENSE("GPL");
> >>
> >> -- 
> >> 2.40.0
> >>
> > 

-- 
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