linux-kernel - Re: [PATCH v6 2/5] usb: cdns3-ti: run HW init at resume() if HW was reset

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Message-ID: <20241214084940.GA4102926@nchen-desktop>
Date: Sat, 14 Dec 2024 16:49:40 +0800
From: Peter Chen <peter.chen@...nel.org>
To: Théo Lebrun <theo.lebrun@...tlin.com>
Cc: Pawel Laszczak <pawell@...ence.com>, Roger Quadros <rogerq@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mathias Nyman <mathias.nyman@...el.com>,
	Grégory Clement <gregory.clement@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/5] usb: cdns3-ti: run HW init at resume() if HW was
 reset

On 24-12-10 18:13:36, Théo Lebrun wrote:
> At runtime_resume(), read the W1 (Wrapper Register 1) register to detect
> if an hardware reset occurred. If it did, run the hardware init sequence.
> 
> This callback will be called at system-wide resume. Previously, if a
> reset occurred during suspend, we would crash. The wrapper config had
> not been written, leading to invalid register accesses inside cdns3.
> 
> Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> ---
>  drivers/usb/cdns3/cdns3-ti.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c
> index d704eb39820ad08a8774be7f00aa473c3ff267c0..d35be7db7616ef5e5bed7dbd53b78a094809f7cc 100644
> --- a/drivers/usb/cdns3/cdns3-ti.c
> +++ b/drivers/usb/cdns3/cdns3-ti.c
> @@ -188,6 +188,12 @@ static int cdns_ti_probe(struct platform_device *pdev)
>  	data->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
>  	data->usb2_only = device_property_read_bool(dev, "ti,usb2-only");
>  
> +	/*
> +	 * The call below to pm_runtime_get_sync() MIGHT reset hardware, if it
> +	 * detects it as uninitialised. We want to enforce a reset at probe,
> +	 * and so do it manually here. This means the first runtime_resume()
> +	 * will be a no-op.
> +	 */
>  	cdns_ti_reset_and_init_hw(data);
>  
>  	pm_runtime_enable(dev);
> @@ -232,6 +238,24 @@ static void cdns_ti_remove(struct platform_device *pdev)
>  	platform_set_drvdata(pdev, NULL);
>  }
>  
> +static int cdns_ti_runtime_resume(struct device *dev)
> +{
> +	const u32 mask = USBSS_W1_PWRUP_RST | USBSS_W1_MODESTRAP_SEL;
> +	struct cdns_ti *data = dev_get_drvdata(dev);
> +	u32 w1;
> +
> +	w1 = cdns_ti_readl(data, USBSS_W1);
> +	if ((w1 & mask) != mask)
> +		cdns_ti_reset_and_init_hw(data);
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops cdns_ti_pm_ops = {
> +	RUNTIME_PM_OPS(NULL, cdns_ti_runtime_resume, NULL)

Why only runtime resume, but without runtime suspend?

Peter