linux-kernel - Re: [PATCH v1 1/5] phy: amlogic: during USB PHY clkin obtaining, enable it

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Date:   Sun, 16 Apr 2023 22:54:17 +0200
From:   Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To:     Dmitry Rokosov <ddrokosov@...rdevices.ru>
Cc:     gregkh@...uxfoundation.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, neil.armstrong@...aro.org,
        khilman@...libre.com, jbrunet@...libre.com,
        mturquette@...libre.com, vkoul@...nel.org, kishon@...nel.org,
        hminas@...opsys.com, Thinh.Nguyen@...opsys.com,
        yue.wang@...ogic.com, hanjie.lin@...ogic.com,
        kernel@...rdevices.ru, rockosov@...il.com,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org, linux-phy@...ts.infradead.org
Subject: Re: [PATCH v1 1/5] phy: amlogic: during USB PHY clkin obtaining,
 enable it

Hi Dmitry,

On Fri, Apr 14, 2023 at 5:24 PM Dmitry Rokosov <ddrokosov@...rdevices.ru> wrote:
[...]
> -       priv->clk = devm_clk_get(dev, "xtal");
> +       priv->clk = devm_clk_get_enabled(dev, "xtal");
Generally this works fine but I wouldn't recommend this approach if:
- there's some required wait time after the clock has been enabled
(see phy_meson_g12a_usb2_init - there's already some required wait
time after triggering the reset)
- clock gating (for power saving) is needed when the dwc3 driver is
unloaded by the PHY driver is not

In this case: just manually manage the clock in phy_meson_g12a_usb2_{init,exit}


Best regards,
Martin