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Message-ID: <9df27b2a-9071-c02f-3dca-57b6006dcdf1@quicinc.com>
Date:   Tue, 2 May 2023 11:59:41 +0530
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Subject: Re: [PATCH V4 2/3] soc: qcom: boot_stat: Add Driver Support for Boot
 Stats
To:     Pavan Kondeti <quic_pkondeti@quicinc.com>
CC:     Andy Gross <agross@kernel.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <linux-arm-msm@vger.kernel.org>,
        <devicetree@vger.kernel.org>, Sibi Sankar <quic_sibis@quicinc.com>,
        "Rajendra Nayak" <quic_rjendra@quicinc.com>
References: <cover.1681742910.git.quic_schowdhu@quicinc.com>
 <2ef76ce292c059c144e559123a9a54201ae2d0cf.1681742910.git.quic_schowdhu@quicinc.com>
 <20230427041135.GA247926@hu-pkondeti-hyd.qualcomm.com>
Content-Language: en-US
From:   Souradeep Chowdhury <quic_schowdhu@quicinc.com>
In-Reply-To: <20230427041135.GA247926@hu-pkondeti-hyd.qualcomm.com>
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On 4/27/2023 9:41 AM, Pavan Kondeti wrote:
> On Mon, Apr 17, 2023 at 08:38:15PM +0530, Souradeep Chowdhury wrote:
>> All of Qualcomm's proprietary Android boot-loaders capture boot time
>> stats, like the time when the bootloader started execution and at what
>> point the bootloader handed over control to the kernel etc. in the IMEM
>> region. This information is captured in a specific format by this driver
>> by mapping a structure to the IMEM memory region and then accessing the
>> members of the structure to show the information within debugfs file.
>> This information is useful in verifying if the existing boot KPIs have
>> regressed or not. The information is shown in milliseconds, a sample
>> log from sm8450(waipio) device is as follows:-
>>
>> /sys/kernel/debug/146aa6b0.boot_stats # cat abl_time
>> 17898 ms
>> /sys/kernel/debug/146aa6b0.boot_stats # cat pre_abl_time
>> 2879 ms
>>
>> The Module Power Manager(MPM) sleep counter starts ticking at the PBL
>> stage and the timestamp generated by the sleep counter is logged by
>> the Qualcomm proprietary bootloader(ABL) at two points-> First when it
>> starts execution which is logged here as "pre_abl_time" and the second
>> when it is about to load the kernel logged as "abl_time". Documentation
>> details are also added in Documentation/ABI/testing/debugfs-driver-bootstat
>>
>> Signed-off-by: Souradeep Chowdhury <quic_schowdhu@quicinc.com>
>> ---
>>   Documentation/ABI/testing/debugfs-driver-bootstat |  17 ++++
>>   drivers/soc/qcom/Kconfig                          |   9 ++
>>   drivers/soc/qcom/Makefile                         |   1 +
>>   drivers/soc/qcom/boot_stats.c                     | 101 ++++++++++++++++++++++
>>   4 files changed, 128 insertions(+)
>>   create mode 100644 Documentation/ABI/testing/debugfs-driver-bootstat
>>   create mode 100644 drivers/soc/qcom/boot_stats.c
>>
>> diff --git a/Documentation/ABI/testing/debugfs-driver-bootstat b/Documentation/ABI/testing/debugfs-driver-bootstat
>> new file mode 100644
>> index 0000000..2543029
>> --- /dev/null
>> +++ b/Documentation/ABI/testing/debugfs-driver-bootstat
>> @@ -0,0 +1,17 @@
>> +What:		/sys/kernel/debug/...stats/pre_abl_time
>> +Date:           April 2023
>> +Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
>> +Description:
>> +		This file is used to read the KPI value pre abl time.
>> +		It shows the time in milliseconds from the starting
>> +		point of PBL to the point when the control shifted
>> +		to ABL(Qualcomm proprietary bootloader).
>> +
>> +What:           /sys/kernel/debug/...stats/abl_time
>> +Date:           April 2023
>> +Contact:        Souradeep Chowdhury <quic_schowdhu@quicinc.com>
>> +Description:
>> +		This file is used to read the KPI value abl time.
>> +		It show the duration in milliseconds from the
>> +		time control switched to ABL to the point when
>> +		the linux kernel started getting loaded.
>> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
>> index a8f2830..0d2cbd3 100644
>> --- a/drivers/soc/qcom/Kconfig
>> +++ b/drivers/soc/qcom/Kconfig
>> @@ -16,6 +16,15 @@ config QCOM_AOSS_QMP
>>   	  subsystems as well as controlling the debug clocks exposed by the Always On
>>   	  Subsystem (AOSS) using Qualcomm Messaging Protocol (QMP).
>>   
>> +config QCOM_BOOTSTAT
>> +	tristate "Qualcomm Technologies, Boot Stat driver"
>> +	depends on ARCH_QCOM || COMPILE_TEST
>> +	help
>> +	  This option enables driver support for boot stats. Boot stat driver logs
>> +	  the kernel bootloader information by accessing the imem region. These
>> +	  information are exposed in the form of debugfs files. This is used to
>> +	  determine if there is any regression in boot timings.
> 
> should this driver depend on DEBUG_FS?

Ack

> 
>> +
>>   config QCOM_COMMAND_DB
>>   	tristate "Qualcomm Command DB"
>>   	depends on ARCH_QCOM || COMPILE_TEST
>> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
>> index 6e88da8..bdaa41a 100644
>> --- a/drivers/soc/qcom/Makefile
>> +++ b/drivers/soc/qcom/Makefile
>> @@ -1,6 +1,7 @@
>>   # SPDX-License-Identifier: GPL-2.0
>>   CFLAGS_rpmh-rsc.o := -I$(src)
>>   obj-$(CONFIG_QCOM_AOSS_QMP) +=	qcom_aoss.o
>> +obj-$(CONFIG_QCOM_BOOTSTAT) += boot_stats.o
>>   obj-$(CONFIG_QCOM_GENI_SE) +=	qcom-geni-se.o
>>   obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o
>>   obj-$(CONFIG_QCOM_CPR)		+= cpr.o
>> diff --git a/drivers/soc/qcom/boot_stats.c b/drivers/soc/qcom/boot_stats.c
>> new file mode 100644
>> index 0000000..7fa8efb
>> --- /dev/null
>> +++ b/drivers/soc/qcom/boot_stats.c
>> @@ -0,0 +1,101 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (c) 2013-2019, 2021 The Linux Foundation. All rights reserved.
>> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved.
>> + */
>> +
>> +#include <linux/debugfs.h>
>> +#include <linux/err.h>
>> +#include <linux/io.h>
>> +#include <linux/init.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/of_address.h>
>> +#include <linux/platform_device.h>
>> +
>> +#define TO_MS(timestamp) ((timestamp * 1000) / 32768)
>> +
>> +/**
>> + *  struct boot_stats - timestamp information related to boot stats
>> + *  @abl_start: Time for the starting point of the abl
>> + *  @abl_end: Time when the kernel starts loading from abl
>> + */
>> +struct boot_stats {
>> +	u32 abl_start;
>> +	u32 abl_end;
>> +} __packed;
>> +
>> +struct bs_data {
>> +	struct boot_stats __iomem *b_stats;
>> +	struct dentry *dbg_dir;
>> +};
>> +
>> +static int abl_time_show(struct seq_file *seq, void *v)
>> +{
>> +	struct boot_stats *boot_stats = seq->private;
>> +	u32 abl_time = TO_MS(boot_stats->abl_end) - TO_MS(boot_stats->abl_start);
>> +
>> +	seq_printf(seq, "%u ms\n", abl_time);
>> +	return 0;
>> +}
>> +DEFINE_SHOW_ATTRIBUTE(abl_time);
>> +
>> +static int pre_abl_time_show(struct seq_file *seq, void *v)
>> +{
>> +	struct boot_stats *boot_stats = seq->private;
>> +
>> +	seq_printf(seq, "%u ms\n", TO_MS(boot_stats->abl_start));
>> +	return 0;
>> +}
>> +DEFINE_SHOW_ATTRIBUTE(pre_abl_time);
>> +
>> +static int boot_stats_probe(struct platform_device *pdev)
>> +{
>> +	struct device *bootstat_dev = &pdev->dev;
>> +	struct bs_data *drvdata;
>> +
>> +	drvdata = devm_kzalloc(bootstat_dev, sizeof(*drvdata), GFP_KERNEL);
> 
> Error handling missing.

Ack

> 
>> +	platform_set_drvdata(pdev, drvdata);
>> +
>> +	drvdata->dbg_dir = debugfs_create_dir(dev_name(bootstat_dev), NULL);
>> +	if (IS_ERR(drvdata->dbg_dir))
>> +		return dev_err_probe(bootstat_dev, -ENOENT, "failed to create debugfs directory");
> 
> %s/-ENOENT/PTR_ERR(drvdata->dbg_dir)

Ack

> 
>> +
>> +	drvdata->b_stats = devm_of_iomap(bootstat_dev, bootstat_dev->of_node, 0, NULL);
>> +	if (!drvdata->b_stats)
>> +		return dev_err_probe(bootstat_dev, -ENOMEM, "failed to map imem region\n");
> 
> The error handling for devm_of_iomap() is different from usual
> ioremap(). you should check for IS_ERR() and return the error code
> approriately. Also when it fails, undo the stuff done above i.e delete
> the debugfs directory.

Ack

> 
>> +
>> +	debugfs_create_file("pre_abl_time", 0200, drvdata->dbg_dir,
>> +			    drvdata->b_stats, &pre_abl_time_fops);
>> +	debugfs_create_file("abl_time", 0200, drvdata->dbg_dir, drvdata->b_stats, &abl_time_fops);
> 
> Why 0200 permissions for read only entries?
> 
> Also consider using debugfs_create_str() which makes your driver
> simpler.

Ack

> 
>> +
>> +	return 0;
>> +}
>> +
>> +void boot_stats_remove(struct platform_device *pdev)
> 
> static?

Ack

> 
>> +{
>> +	struct bs_data *drvdata = platform_get_drvdata(pdev);
>> +
>> +	debugfs_remove_recursive(drvdata->dbg_dir);
>> +	iounmap(drvdata->b_stats);
> 
> since you used devm_of_iomap(), explicit iounmap is not needed.

Ack

> 
>> +}
>> +
>> +static const struct of_device_id boot_stats_dt_match[] = {
>> +	{ .compatible = "qcom,sm8450-bootstats" },
>> +	{ }
>> +};
>> +MODULE_DEVICE_TABLE(of, boot_stats_dt_match);
>> +
>> +static struct platform_driver boot_stat_driver = {
>> +	.probe  = boot_stats_probe,
>> +	.remove_new = boot_stats_remove,
>> +	.driver = {
>> +		.name = "qcom-boot-stats",
>> +		.of_match_table = boot_stats_dt_match,
>> +	},
>> +};
>> +module_platform_driver(boot_stat_driver);
>> +
>> +MODULE_DESCRIPTION("Qualcomm Technologies Inc. Boot Stat driver");
>> +MODULE_LICENSE("GPL");
>> -- 
>> 2.7.4
>>
> Thanks,
> Pavan