linux-kernel - Re: [PATCH V1 3/4] soc: qcom: boot_stat: Add Driver Support for Boot Stats

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Message-ID: <321005fc-1bfd-c04d-b2b5-d85d213ac00a@quicinc.com>
Date:   Wed, 22 Mar 2023 19:24:16 +0530
From:   Souradeep Chowdhury <quic_schowdhu@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Sibi Sankar <quic_sibis@...cinc.com>,
        Rajendra Nayak <quic_rjendra@...cinc.com>
Subject: Re: [PATCH V1 3/4] soc: qcom: boot_stat: Add Driver Support for Boot
 Stats



On 3/21/2023 11:07 PM, Krzysztof Kozlowski wrote:
> On 21/03/2023 14:51, 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 print the information. This information is
>> useful in verifying if the existing boot KPIs have regre
> 
> 
>> +/**
>> + *  struct boot_stats - timestamp information related to boot stats
>> + *  @bootloader_start:	Time for the starting point of the abl bootloader
>> + *  @bootloader_end:	Time when the kernel starts loading from abl bootloader
>> + */
>> +struct boot_stats {
>> +	u32 bootloader_start;
>> +	u32 bootloader_end;
>> +} __packed;
>> +
>> +static struct boot_stats __iomem *boot_stats;
>> +static void __iomem *mpm_counter_base;
>> +static u32 mpm_counter_freq;
> 
> No file-scope variables. Does not scale, not easy for review and
> maintenance. Avoid such code.

Ack
> 
>> +
>> +static int mpm_parse_dt(void)
>> +{
>> +	struct device_node *np_imem, *np_mpm2;
>> +
>> +	np_imem = of_find_compatible_node(NULL, NULL,
>> +					  "qcom,imem-boot_stats");
>> +	if (!np_imem) {
>> +		pr_err("can't find qcom,imem node\n");
> 
> So you are printing errors everywhere, on every soc and with compile
> test on every platform there is in the world... sorry, it does not work
> like that.

Ack
> 
>> +		return -ENODEV;
>> +	}
>> +	boot_stats = of_iomap(np_imem, 0);
>> +	if (!boot_stats) {
>> +		pr_err("boot_stats: Can't map imem\n");
>> +		goto err1;
>> +	}
> 
> 
>> +
>> +static void __exit boot_stats_exit(void)
>> +{
>> +}
>> +module_exit(boot_stats_exit)
> 
> 
> I don't think this is some special code which deserves init calls. Make
> it module_platform_driver().

Since this just reads some values from the Imem region and prints it to 
the user and doesn't have a specific device associated with it, a 
generic module code is written for it and not a module_platform_driver().

> 
> 
> Best regards,
> Krzysztof
>