Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210617194154.2397-1-linux.amoon@gmail.com> <20210617194154.2397-8-linux.amoon@gmail.com>
In-Reply-To: <20210617194154.2397-8-linux.amoon@gmail.com>
From:   Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Date:   Fri, 18 Jun 2021 00:37:02 +0200
Message-ID: <CAFBinCC0KScn6cJ36ZB_=TRncOOCXJHWwR3s=o3TobH=yOrGJA@mail.gmail.com>
Subject: Re: [RFCv1 7/8] phy: amlogic: meson8b-usb2: Power off the PHY by
 putting it into reset mode.
To:     Anand Moon <linux.amoon@gmail.com>
Cc:     Kishon Vijay Abraham I <kishon@ti.com>,
        Vinod Koul <vkoul@kernel.org>,
        Neil Armstrong <narmstrong@baylibre.com>,
        Kevin Hilman <khilman@baylibre.com>,
        Jerome Brunet <jbrunet@baylibre.com>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        linux-phy@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Anand,

On Thu, Jun 17, 2021 at 9:44 PM Anand Moon <linux.amoon@gmail.com> wrote:
[...]
> @@ -245,8 +250,6 @@ static int phy_meson8b_usb2_power_on(struct phy *phy)
>         regmap_update_bits(priv->regmap, REG_CTRL, REG_CTRL_FSEL_MASK,
>                            0x5 << REG_CTRL_FSEL_SHIFT);
>         /* reset the PHY */
> -       regmap_update_bits(priv->regmap, REG_CTRL, REG_CTRL_POWER_ON_RESET,
> -                          REG_CTRL_POWER_ON_RESET);
The vendor driver uses the following sequence for the power on reset:
- set the power on reset bit
- wait 500us
- clear the power on reset bit
- wait 500us

With your change we now:
- wait 500us
- clear the power on reset bit
- wait 500us

I don't know if this is sufficient to bring the PHY into a well-defined state.
Maybe it works, maybe it doesn't reset at all in this case - I don't
know how to verify this though.


Best regards,
Martin