Re: [PATCH] usb: phy: tegra: Fix phy suspend for UDC

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

Adding Dmitry ...

Felipe, Thierry, this is needed for v4.14-rc because suspend is currently
broken for some Tegra devices.

Jon

On 29/09/17 14:06, Jon Hunter wrote:
> Commit dfebb5f43a78 ("usb: chipidea: Add support for Tegra20/30/114/124")
> added UDC support for Tegra but with UDC support enabled, is was found
> that Tegra30, Tegra114 and Tegra124 would hang on entry to suspend.
> 
> The hang occurred during the suspend of the USB PHY when the Tegra PHY
> driver attempted to disable the PHY clock. The problem is that before
> the Tegra PHY driver is suspended, the chipidea driver already disabled
> the PHY clock and when the Tegra PHY driver suspended, it could not read
> DEVLC register and caused the device to hang.
> 
> The Tegra USB PHY driver is used by both the Tegra EHCI driver and now
> the chipidea UDC driver and so simply removing the disabling of the PHY
> clock from the USB PHY driver would not work for the Tegra EHCI driver.
> Fortunately, the status of the USB PHY clock can be read from the
> USB_SUSP_CTRL register and therefore, to workaround this issue, simply
> poll the register prior to disabling the clock in USB PHY driver to see
> if clock gating has already been initiated. Please note that it can take
> a few uS for the clock to disable and so simply reading this status
> register once on entry is not sufficient.
> 
> Please note that no issues are seen with Tegra20 because it has a slightly
> different PHY to Tegra30/114/124.
>

I forgot the fixes tag ...

Fixes: dfebb5f43a78 ("usb: chipidea: Add support for Tegra20/30/114/124")
 
> Signed-off-by: Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/usb/phy/phy-tegra-usb.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/usb/phy/phy-tegra-usb.c b/drivers/usb/phy/phy-tegra-usb.c
> index 5fe4a5704bde..c8fff99bd16e 100644
> --- a/drivers/usb/phy/phy-tegra-usb.c
> +++ b/drivers/usb/phy/phy-tegra-usb.c
> @@ -329,6 +329,14 @@ static void utmi_phy_clk_disable(struct tegra_usb_phy *phy)
>  	unsigned long val;
>  	void __iomem *base = phy->regs;
>  
> +	/*
> +	 * The USB driver may have already initiated the phy clock
> +	 * disable so wait to see if the clock turns off and if not
> +	 * then proceed with gating the clock.
> +	 */
> +	if (utmi_wait_register(base + USB_SUSP_CTRL, USB_PHY_CLK_VALID, 0) == 0)
> +		return;
> +
>  	if (phy->is_legacy_phy) {
>  		val = readl(base + USB_SUSP_CTRL);
>  		val |= USB_SUSP_SET;
> 

-- 
nvpublic
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