linux-kernel - Re: [PATCH v4 3/3] ata: ahci_tegra: Add AHCI support for Tegra186

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Message-ID: <49eba27e-18fa-b682-1385-2930dfff28ac@nvidia.com>
Date:   Wed, 7 Apr 2021 15:57:33 -0700
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <axboe@...nel.dk>,
        <thierry.reding@...il.com>, <jonathanh@...dia.com>,
        <robh+dt@...nel.org>
CC:     <pchandru@...dia.com>, <devicetree@...r.kernel.org>,
        <linux-ide@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3/3] ata: ahci_tegra: Add AHCI support for Tegra186

On 4/7/21 2:36 PM, Dmitry Osipenko wrote:
> 07.04.2021 04:25, Sowjanya Komatineni пишет:
>> +	if (!tegra->pdev->dev.pm_domain) {
>> +		ret = tegra_powergate_sequence_power_up(TEGRA_POWERGATE_SATA,
>> +							tegra->sata_clk,
>> +							tegra->sata_rst);
>> +		if (ret)
>> +			goto disable_regulators;
>> +	}
>>   
> Hi,
>
> Why you haven't added condition for tegra_powergate_power_off()? I think
> it should break GENPD and legacy PD API isn't not supported by T186 at all.
>
> I'm also not sure whether the power up/down sequence is correct using GENPD.
>
> Moreover the driver doesn't support runtime PM, so GENPD should be
> always off?

This driver already using legacy PD API's so thought its supported and 
added power domain device check during powergate_sequence_power_up and 
yes same should apply for powergate_power_off as well. But if legacy PD 
is not supported by T186 then not sure why original driver even using 
these API's.

Preetham/Thierry, Can you please comment ?

But as RPM is not implemented yet for this driver, GENPD will be OFF but 
SATA is not in power-gate by the time kernel starts and functionally works.

But with RPM implementation, I guess we can do proper power gate on/off.