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

[Roger Quadros <rogerq@kernel.org>]

On 10/12/2024 19:13, 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.
> 

Did I understand right that the Controller reset can happen only at
system suspend and never at runtime suspend?

If so do you really need the runtime suspend/resume hooks?
you should have different system suspend/resume hooks than runtime suspend/resume
hooks and deal with the re-initialization in system resume hook.


> Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.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.
> +	 */

Separate system sleep hooks will also prevent this kind of behavior.

>  	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)
> +	SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
> +};
> +
>  static const struct of_device_id cdns_ti_of_match[] = {
>  	{ .compatible = "ti,j721e-usb", },
>  	{ .compatible = "ti,am64-usb", },
> @@ -245,6 +269,7 @@ static struct platform_driver cdns_ti_driver = {
>  	.driver		= {
>  		.name	= "cdns3-ti",
>  		.of_match_table	= cdns_ti_of_match,
> +		.pm     = pm_ptr(&cdns_ti_pm_ops),
>  	},
>  };
>  
> 

-- 
cheers,
-roger