linux-kernel - Re: [PATCH v6 04/15] phy: tegra: xusb: tegra210: Do not reset UPHY PLL

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Date:   Tue, 19 Jan 2021 14:52:00 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     JC Kuo <jckuo@...dia.com>
Cc:     gregkh@...uxfoundation.org, robh@...nel.org, jonathanh@...dia.com,
        kishon@...com, linux-tegra@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, nkristam@...dia.com
Subject: Re: [PATCH v6 04/15] phy: tegra: xusb: tegra210: Do not reset UPHY
 PLL

On Tue, Jan 19, 2021 at 04:55:35PM +0800, JC Kuo wrote:
> Once UPHY PLL hardware power sequencer is enabled, do not assert
> reset to PEX/SATA PLLs, otherwise UPHY PLL operation will be broken.
> This commit removes reset_control_assert(pcie->rst) and
> reset_control_assert(sata->rst) from PEX/SATA UPHY disable procedure.
> 
> Signed-off-by: JC Kuo <jckuo@...dia.com>
> ---
> v6:
>    no change
> v5:
>    no change
> v4:
>    no change
> v3:
>    new, was a part of "phy: tegra: xusb: Rearrange UPHY init on Tegra210"
> 
>  drivers/phy/tegra/xusb-tegra210.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/phy/tegra/xusb-tegra210.c b/drivers/phy/tegra/xusb-tegra210.c
> index 4dc9286ec1b8..9bfecdfecf35 100644
> --- a/drivers/phy/tegra/xusb-tegra210.c
> +++ b/drivers/phy/tegra/xusb-tegra210.c
> @@ -502,7 +502,6 @@ static void tegra210_pex_uphy_disable(struct tegra_xusb_padctl *padctl)
>  	if (--pcie->enable > 0)
>  		return;
>  
> -	reset_control_assert(pcie->rst);
>  	clk_disable_unprepare(pcie->pll);
>  }
>  
> @@ -739,7 +738,6 @@ static void tegra210_sata_uphy_disable(struct tegra_xusb_padctl *padctl)
>  	if (--sata->enable > 0)
>  		return;
>  
> -	reset_control_assert(sata->rst);
>  	clk_disable_unprepare(sata->pll);
>  }

Isn't this going to break things between here and patch 5 where the
hardware sequencer is enabled? If so, it might be better to move this
into patch 5 so that things stay functional and bisectible.

Thierry

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