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Message-Id: <CZNLFUH8WWIA.MAUN8E53X7PK@bootlin.com>
Date: Thu, 07 Mar 2024 15:39:15 +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: "Thomas Petazzoni" <thomas.petazzoni@...tlin.com>,
Grégory Clement <gregory.clement@...tlin.com>, "Kevin
Hilman" <khilman@...nel.org>, "Alan Stern" <stern@...land.harvard.edu>,
<linux-usb@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 3/9] usb: cdns3-ti: move reg writes from probe into
->runtime_resume()
Hello Roger,
On Thu Mar 7, 2024 at 1:31 PM CET, Roger Quadros wrote:
> Hi,
>
> On 07/03/2024 11:55, Théo Lebrun wrote:
> > The hardware initialisation register write sequence is only used at
> > probe. Move it from being done at explicitely at probe to being done
> > implicitely by pm_runtime_get_sync() that calls ->runtime_resume().
>
> explicitly / implicitly
>
> >
> > Keep devicetree parsing in probe and add a new field in the private
> > struct to remember the USB2 refclk rate code computation result.
> >
> > This opens the door to having the init sequence being executed later
> > down the road, at system-wide resume for example. This is NOT currently
> > happening because runtime PM is disabled at suspend without the
> > refcount being affected.
> >
> > Signed-off-by: Théo Lebrun <theo.lebrun@...tlin.com>
> > ---
> > drivers/usb/cdns3/cdns3-ti.c | 90 +++++++++++++++++++++++++-------------------
> > 1 file changed, 52 insertions(+), 38 deletions(-)
> >
> > diff --git a/drivers/usb/cdns3/cdns3-ti.c b/drivers/usb/cdns3/cdns3-ti.c
> > index 5945c4b1e11f..4c8a557e6a6f 100644
> > --- a/drivers/usb/cdns3/cdns3-ti.c
> > +++ b/drivers/usb/cdns3/cdns3-ti.c
> > @@ -57,6 +57,7 @@ struct cdns_ti {
> > unsigned vbus_divider:1;
> > struct clk *usb2_refclk;
> > struct clk *lpm_clk;
> > + int usb2_refclk_rate_code;
> > };
> >
> > static const int cdns_ti_rate_table[] = { /* in KHZ */
> > @@ -90,10 +91,8 @@ 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;
> >
> > data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > if (!data)
> > @@ -133,7 +132,9 @@ static int cdns_ti_probe(struct platform_device *pdev)
> > return -EINVAL;
> > }
> >
> > - rate_code = i;
> > + data->usb2_refclk_rate_code = i;
> > + data->vbus_divider = device_property_read_bool(dev, "ti,vbus-divider");
> > + data->usb2_only = device_property_read_bool(dev, "ti,usb2-only");
> >
> > pm_runtime_enable(dev);
> > error = pm_runtime_get_sync(dev);
> > @@ -142,40 +143,6 @@ 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);
> > -
> > - /* de-assert RESET */
> > - reg |= USBSS_W1_PWRUP_RST;
> > - cdns_ti_writel(data, USBSS_W1, reg);
> > -
> > error = of_platform_populate(node, NULL, NULL, dev);
> > if (error) {
> > dev_err(dev, "failed to create children: %d\n", error);
> > @@ -211,6 +178,52 @@ static void cdns_ti_remove(struct platform_device *pdev)
> > platform_set_drvdata(pdev, NULL);
> > }
> >
> > +static int cdns_ti_runtime_resume(struct device *dev)
> > +{
> > + struct cdns_ti *data = dev_get_drvdata(dev);
> > + u32 reg;
> > +
> > + /* 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 |= data->usb2_refclk_rate_code << USBSS1_STATIC_PLL_REF_SEL_SHIFT;
> > +
> > + reg &= ~USBSS1_STATIC_VBUS_SEL_MASK;
> > +
> > + 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);
> > +
> > + 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);
> > +
> > + /* de-assert RESET */
> > + reg |= USBSS_W1_PWRUP_RST;
> > + cdns_ti_writel(data, USBSS_W1, reg);
>
> I don't think USB controller requires a reset and re-init between
> runtime suspend/resume.
>
> What you need is reset/re-init during system Resume on certain platforms.
> So you should move this part of code into a helper function and call it
> from .probe() and .system_resume()
Runtime resume is being called at probe() and system-wide resume. See
our runtime_resume() implementation as that helper function you are
describing.
A previous revision did what you are recommending. We leaned towards the
current version. See:
https://lore.kernel.org/lkml/7h34wxfmwn.fsf@baylibre.com/
Also, assuming we enable runtime PM, a reset and re-init after runtime
suspend would be the right thing to do anyways. My reading of
drivers/pmdomain/core.c tells me that if our device goes to runtime
suspend, domains will be shut down. Our controller will be reset and
we'll need to re-init it. The GENPD_FLAG_RPM_ALWAYS_ON flag is of
interest to avoid the PD to be shut down during runtime PM.
Regards,
--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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