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([2a02:810d:15c0:828:ce50:243f:54cc:5373]) by smtp.gmail.com with ESMTPSA id wy8-20020a170906fe0800b0093e261cc8bcsm612167ejb.58.2023.03.24.01.56.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Mar 2023 01:56:16 -0700 (PDT) Message-ID: <58316fc3-1ee1-b530-e783-ccd8225e07d6@linaro.org> Date: Fri, 24 Mar 2023 09:56:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH V1 3/4] soc: qcom: boot_stat: Add Driver Support for Boot Stats Content-Language: en-US To: Souradeep Chowdhury , Andy Gross , Konrad Dybcio , Krzysztof Kozlowski , Bjorn Andersson , Rob Herring Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, devicetree@vger.kernel.org, Sibi Sankar , Rajendra Nayak References: <3f385562845ae26d519940ca8098fde89282991b.1679403696.git.quic_schowdhu@quicinc.com> <611ea918-64a6-f306-b5ec-db55e41abda2@linaro.org> <321005fc-1bfd-c04d-b2b5-d85d213ac00a@quicinc.com> <7b939818-993a-e849-e7e0-ae9ea74ea52b@linaro.org> <5c4df95e-fb44-e873-7ecc-dec381a42aff@quicinc.com> From: Krzysztof Kozlowski In-Reply-To: <5c4df95e-fb44-e873-7ecc-dec381a42aff@quicinc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/03/2023 14:45, Souradeep Chowdhury wrote: > > > On 3/22/2023 8:23 PM, Krzysztof Kozlowski wrote: >> On 22/03/2023 14:54, Souradeep Chowdhury wrote: >>> >>> >>> 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 >> >> Which is not really an argument for such antipattern, but okay... >> >>> generic module code is written for it and not a module_platform_driver(). >> >> ... so how do you handle deferred probe? > > This has no dependency on other resources except that it parses some > information from DT nodes, so deferred probe handling is not needed > in this case. Yes, I know, but if we would ever add it how this driver can handle it? This is antipattern. Best regards, Krzysztof