[PATCH] phy: lantiq: rcu-usb2: wait after clock enable

[PATCH] phy: lantiq: rcu-usb2: wait after clock enable

[Mathias Kresin]

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>
---
 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;
 }
-- 
2.25.1

Re: [PATCH] phy: lantiq: rcu-usb2: wait after clock enable

[Hauke Mehrtens]

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;
>   }
> 

Re: [PATCH] phy: lantiq: rcu-usb2: wait after clock enable

[Martin Blumenstingl]

On Thu, Jan 7, 2021 at 11:49 PM Mathias Kresin <dev@kresin.me> 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: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

Re: [PATCH] phy: lantiq: rcu-usb2: wait after clock enable

[Vinod Koul]

On 07-01-21, 23:49, 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.

Applied, thanks

-- 
~Vinod