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

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Date:   Tue, 21 Mar 2023 18:37:25 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Souradeep Chowdhury <quic_schowdhu@...cinc.com>,
        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 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.

> +
> +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.

> +		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().


Best regards,
Krzysztof