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Date:   Fri, 13 Jan 2023 17:55:44 +0530
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Subject: Re: [Patch v1 01/10] memory: tegra: add interconnect support for DRAM
 scaling in Tegra234
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To:     Dmitry Osipenko <digetx@gmail.com>, <treding@nvidia.com>,
        <krzysztof.kozlowski@linaro.org>, <dmitry.osipenko@collabora.com>,
        <viresh.kumar@linaro.org>, <rafael@kernel.org>,
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        <linux-pm@vger.kernel.org>, <devicetree@vger.kernel.org>
CC:     <sanjayc@nvidia.com>, <ksitaraman@nvidia.com>, <ishah@nvidia.com>,
        <bbasu@nvidia.com>, Sumit Gupta <sumitg@nvidia.com>
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 <20221220160240.27494-2-sumitg@nvidia.com>
 <8641fad2-7170-4c0c-fbd6-6e2e784b3106@gmail.com>
From:   Sumit Gupta <sumitg@nvidia.com>
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On 21/12/22 22:24, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
> 
> 
> 20.12.2022 19:02, Sumit Gupta пишет:
>>   static int tegra186_emc_probe(struct platform_device *pdev)
>>   {
>>        struct mrq_emc_dvfs_latency_response response;
>>        struct tegra_bpmp_message msg;
>>        struct tegra186_emc *emc;
>> +     struct tegra_mc *mc;
>>        unsigned int i;
>>        int err;
>>
>> @@ -158,6 +307,9 @@ static int tegra186_emc_probe(struct platform_device *pdev)
>>        if (!emc)
>>                return -ENOMEM;
>>
>> +     platform_set_drvdata(pdev, emc);
>> +     emc->dev = &pdev->dev;
>> +
>>        emc->bpmp = tegra_bpmp_get(&pdev->dev);
>>        if (IS_ERR(emc->bpmp))
>>                return dev_err_probe(&pdev->dev, PTR_ERR(emc->bpmp), "failed to get BPMP\n");
>> @@ -236,6 +388,19 @@ static int tegra186_emc_probe(struct platform_device *pdev)
>>        debugfs_create_file("max_rate", S_IRUGO | S_IWUSR, emc->debugfs.root,
>>                            emc, &tegra186_emc_debug_max_rate_fops);
>>
>> +     mc = dev_get_drvdata(emc->dev->parent);
>> +     if (mc && mc->soc->icc_ops) {
>> +             if (tegra_bpmp_mrq_is_supported(emc->bpmp, MRQ_BWMGR_INT)) {
>> +                     err = tegra_emc_interconnect_init(emc);
>> +                     if (!err)
>> +                             return err;
>> +                     dev_err(&pdev->dev, "tegra_emc_interconnect_init failed:%d\n", err);
>> +                     goto put_bpmp;
>> +             } else {
>> +                     dev_info(&pdev->dev, "MRQ_BWMGR_INT not present\n");
>> +             }
> 
> If there is no MRQ_BWMGR_INT, then device drivers using ICC won't probe.
> This is either a error condition, or ICC should inited and then ICC
> changes should be skipped.
> 

If the MRQ_BW_MGR is not supported by a BPMP-FW binary, then the MC & 
EMC drivers will still probe successfully and scaling will be disabled.