linux-kernel - Re: [PATCH 2/6] usb: cdns3-ti: move reg writes from probe into an init

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Message-Id: <CWZGC158AQK7.2XQXIEEH6WO2J@tleb-bootlin-xps13-01>
Date:   Wed, 15 Nov 2023 15:23:15 +0100
From:   Théo Lebrun <theo.lebrun@...tlin.com>
To:     "Roger Quadros" <rogerq@...nel.org>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        "Krzysztof Kozlowski" <krzysztof.kozlowski+dt@...aro.org>,
        "Conor Dooley" <conor+dt@...nel.org>,
        "Peter Chen" <peter.chen@...nel.org>,
        "Pawel Laszczak" <pawell@...ence.com>,
        "Nishanth Menon" <nm@...com>,
        "Vignesh Raghavendra" <vigneshr@...com>,
        "Tero Kristo" <kristo@...nel.org>
Cc:     <linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/6] usb: cdns3-ti: move reg writes from probe into an
 init_hw helper

Hello,

On Wed Nov 15, 2023 at 12:33 PM CET, Roger Quadros wrote:
> > --- a/drivers/usb/cdns3/cdns3-ti.c
> > +++ b/drivers/usb/cdns3/cdns3-ti.c

[...]

> >  static int cdns_ti_probe(struct platform_device *pdev)
> >  {
> >  	struct device *dev = &pdev->dev;
> >  	struct device_node *node = pdev->dev.of_node;
> >  	struct cdns_ti *data;
> > -	int error;
> > -	u32 reg;
> > -	int rate_code, i;
> >  	unsigned long rate;
> > +	int error, i;
>
> Should we leave rate_code and get rid of i?

I see your point about i being usually a temp variable. Using rate_code
instead of i means the for-loop becomes rather long (column 87) &
should ideally be split.

How about moving the data->usb2_refclk_rate_code assignment up, closer
to the computation of i? That way we don't reference i three blocks
down the road, seemingly out of nowhere.

Regards,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

------------------------------------------------------------------------

> >  	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> >  	if (!data)
> > @@ -133,8 +169,6 @@ static int cdns_ti_probe(struct platform_device *pdev)
> >  		return -EINVAL;
> >  	}
> >  
> > -	rate_code = i;
> > -
> >  	pm_runtime_enable(dev);
> >  	error = pm_runtime_get_sync(dev)>  	if (error < 0) {
> > @@ -142,39 +176,11 @@ static int cdns_ti_probe(struct platform_device *pdev)
> >  		goto err;
> >  	}
> >  
> > -	/* assert RESET */
> > -	reg = cdns_ti_readl(data, USBSS_W1);
> > -	reg &= ~USBSS_W1_PWRUP_RST;
> > -	cdns_ti_writel(data, USBSS_W1, reg);
> > -
> > -	/* set static config */
> > -	reg = cdns_ti_readl(data, USBSS_STATIC_CONFIG);
> > -	reg &= ~USBSS1_STATIC_PLL_REF_SEL_MASK;
> > -	reg |= rate_code << USBSS1_STATIC_PLL_REF_SEL_SHIFT;
> > -
> > -	reg &= ~USBSS1_STATIC_VBUS_SEL_MASK;
> >  	data->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
> > -	if (data->vbus_divider)
> > -		reg |= 1 << USBSS1_STATIC_VBUS_SEL_SHIFT;
> > -
> > -	cdns_ti_writel(data, USBSS_STATIC_CONFIG, reg);
> > -	reg = cdns_ti_readl(data, USBSS_STATIC_CONFIG);
> > -
> > -	/* set USB2_ONLY mode if requested */
> > -	reg = cdns_ti_readl(data, USBSS_W1);
> >  	data->usb2_only = device_property_read_bool(dev, "ti,usb2-only");
> > -	if (data->usb2_only)
> > -		reg |= USBSS_W1_USB2_ONLY;
> > -
> > -	/* set default modestrap */
> > -	reg |= USBSS_W1_MODESTRAP_SEL;
> > -	reg &= ~USBSS_W1_MODESTRAP_MASK;
> > -	reg |= USBSS_MODESTRAP_MODE_NONE << USBSS_W1_MODESTRAP_SHIFT;
> > -	cdns_ti_writel(data, USBSS_W1, reg);
> > +	data->usb2_refclk_rate_code = i;
>
> because 'i' seems temporary.
>
> >  
> > -	/* de-assert RESET */
> > -	reg |= USBSS_W1_PWRUP_RST;
> > -	cdns_ti_writel(data, USBSS_W1, reg);
> > +	cdns_ti_init_hw(data);
> >  
> >  	error = of_platform_populate(node, NULL, NULL, dev);
> >  	if (error) {
> >