linux-kernel - Re: [Patch v4 03/10] memory: tegra: add interconnect support for DRAM scaling in Tegra234

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Message-ID: <8139e102-677d-6850-b1c3-7a35e0e36904@nvidia.com>
Date:   Tue, 28 Mar 2023 18:00:32 +0530
From:   Sumit Gupta <sumitg@...dia.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     <treding@...dia.com>, <dmitry.osipenko@...labora.com>,
        <viresh.kumar@...aro.org>, <rafael@...nel.org>,
        <jonathanh@...dia.com>, <robh+dt@...nel.org>,
        <lpieralisi@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        <mmaddireddy@...dia.com>, <kw@...ux.com>, <bhelgaas@...gle.com>,
        <vidyas@...dia.com>, <sanjayc@...dia.com>, <ksitaraman@...dia.com>,
        <ishah@...dia.com>, <bbasu@...dia.com>,
        Sumit Gupta <sumitg@...dia.com>
Subject: Re: [Patch v4 03/10] memory: tegra: add interconnect support for DRAM
 scaling in Tegra234



On 28/03/23 16:35, Thierry Reding wrote:
> On Tue, Mar 28, 2023 at 09:31:58AM +0200, Krzysztof Kozlowski wrote:
>> On 27/03/2023 18:14, Sumit Gupta wrote:
> [...]
>>> diff --git a/drivers/memory/tegra/tegra186-emc.c b/drivers/memory/tegra/tegra186-emc.c
> [...]
>>> @@ -158,6 +260,9 @@ static int tegra186_emc_probe(struct platform_device *pdev)
>>>   	if (!emc)
>>>   		return -ENOMEM;
>>>   
>>> +	platform_set_drvdata(pdev, emc);
>>> +	emc->dev = &pdev->dev;
>>
>> This patch looks like stiched from two or more patches... emc->dev does
>> not look like new member of emc, thus why do you set in exisitng
>> function in this patch? Why it wasn't needed before?
> 
> This looks like it may be leftover from some development. These two
> lines exist in this driver a few lines further down. Either one pair
> should be removed. I don't see why this would need to be moved, so
> probably the above additions can just be dropped.
> 
> Thierry
> 
Yes, sorry i was left over. Will remove this.
Thank you for catching.

>>>   	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 +341,25 @@ 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) {
>>> +		/*
>>> +		 * Initialize the ICC even if BPMP-FW doesn't support 'MRQ_BWMGR_INT'.
>>> +		 * Use the flag 'mc->bwmgr_mrq_supported' within MC driver and return
>>> +		 * EINVAL instead of passing the request to BPMP-FW later when the BW
>>> +		 * request is made by client with 'icc_set_bw()' call.
>>> +		 */
>>> +		err = tegra_emc_interconnect_init(emc);
>>> +		if (err)
>>> +			goto put_bpmp;
>>> +
>>> +		if (tegra_bpmp_mrq_is_supported(emc->bpmp, MRQ_BWMGR_INT))
>>> +			mc->bwmgr_mrq_supported = true;
>>> +		else
>>> +
>>
>> Drop blank line.
>>
Ok.

>>> +			dev_info(&pdev->dev, "MRQ_BWMGR_INT not present\n");
>>
>> And what user is supposed to do with this? Either make it descriptive or
>> drop.
> 
> Agreed. I think we can just drop this. If the intention was to provide a
> quick way for people to detect whether BWMGR is available or not, using
> something from sysfs/debugfs would be preferable.
> 
> Thierry

Sure, will drop this.

Thank you,
Sumit Gupta