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SubjectRe: [PATCH] phy: lantiq: rcu-usb2: wait after clock enable
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On 1/7/21 11:49 PM, Mathias Kresin wrote:
> Commit 65dc2e725286 ("usb: dwc2: Update Core Reset programming flow.")
> revealed that the phy isn't ready immediately after enabling it's
> clocks. The dwc2_check_core_version() fails and the dwc2 usb driver
> errors out.
>
> Add a short delay to let the phy get up and running. There isn't any
> documentation how much time is required, the value was chosen based on
> tests.
>
> Cc: <stable@vger.kernel.org> # v5.7+
> Signed-off-by: Mathias Kresin <dev@kresin.me>

Acked-by: Hauke Mehrtens <hauke@hauke-m.de>

I do not know how long you have to wait here, but this looks ok, when it
works.

Hauke

> ---
> drivers/phy/lantiq/phy-lantiq-rcu-usb2.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c b/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c
> index a7d126192cf1..29d246ea24b4 100644
> --- a/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c
> +++ b/drivers/phy/lantiq/phy-lantiq-rcu-usb2.c
> @@ -124,8 +124,16 @@ static int ltq_rcu_usb2_phy_power_on(struct phy *phy)
> reset_control_deassert(priv->phy_reset);
>
> ret = clk_prepare_enable(priv->phy_gate_clk);
> - if (ret)
> + if (ret) {
> dev_err(dev, "failed to enable PHY gate\n");
> + return ret;
> + }
> +
> + /*
> + * at least the xrx200 usb2 phy requires some extra time to be
> + * operational after enabling the clock
> + */
> + usleep_range(100, 200);
>
> return ret;
> }
>

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