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Message-ID: <miuivpqhatkgtw5g7rl6xj7o4gzxztz6hif53t765elwvhddsq@gqmbxkkabm2y>
Date: Sat, 8 Feb 2025 12:42:14 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Peter Chen <peter.chen@...nel.org>
CC: Siddharth Vadapalli <s-vadapalli@...com>, <pawell@...ence.com>,
<rogerq@...nel.org>, <gregkh@...uxfoundation.org>, <balbi@...nel.org>,
<jun.li@....com>, <linux-usb@...r.kernel.org>,
<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <srk@...com>
Subject: Re: [PATCH] usb: cdns3: exit cdns3_gadget_udc_start if
FAST_REG_ACCESS cannot be set
On Sat, Feb 08, 2025 at 01:39:44PM +0800, Peter Chen wrote:
> On 25-02-07 11:12:50, Siddharth Vadapalli wrote:
> > On Fri, Feb 07, 2025 at 10:25:23AM +0800, Peter Chen wrote:
> >
> > Hello Peter,
> >
> > > On 25-02-06 18:29:36, Siddharth Vadapalli wrote:
> > > > When the device is in a low power state, access to the following
> > > > registers takes a long time:
> > > > - EP_CFG
> > > > - EP_TRADDR
> > > > - EP_CMD
> > > > - EP_SEL
> > > > - EP_STS
> > > > - USB_CONF
[...]
> > > > @@ -2997,6 +2997,20 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
> > > > /* limit speed if necessary */
> > > > max_speed = min(driver->max_speed, gadget->max_speed);
> > > >
> > > > + /* keep Fast Access bit */
> > > > + writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
> > > > + reg = readl(&priv_dev->regs->usb_pwr);
> > > > + if (!(reg & PUSB_PWR_FST_REG_ACCESS_STAT)) {
> > > > + ret = readl_poll_timeout_atomic(&priv_dev->regs->usb_pwr, reg,
> > > > + (reg & PUSB_PWR_FST_REG_ACCESS_STAT),
> > > > + 10, 1000);
> > > > + if (ret) {
> > > > + dev_err(priv_dev->dev, "Failed to enable fast access\n");
> > > > + spin_unlock_irqrestore(&priv_dev->lock, flags);
> > > > + return ret;
> > > > + }
> > > > + }
> > > > +
> > > > switch (max_speed) {
> > > > case USB_SPEED_FULL:
> > > > writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
> > >
> > > Hi Siddharth,
> > >
> > > Would you please keep this change at cdns3_gadget_config in case the
> > > controller is power lost during the system suspend?
> >
> > I did think of that initially, but the problem with doing so is that we
> > are already accessing USB_CONF above in the "switch(max_speed)" section.
> > The PUSB_PWR_FST_REG_ACCESS bit needs to be set before accessing any of:
> > - EP_CFG
> > - EP_TRADDR
> > - EP_CMD
> > - EP_SEL
> > - EP_STS
> > - USB_CONF
> >
> > Please let me know if you have an alternate suggestion to address the
> > above.
> >
>
> How about move cdns3_gadget_config at the beginning of function
> cdns3_gadget_udc_start, and add your changes at cdns3_gadget_config?
Yes, I could do that, but I will still move the following section within
cdns3_gadget_config() function to the top of that function:
/* keep Fast Access bit */
writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
Additionally, I will update cdns3_gadget_config() to return an error
code if Fast Access bit cannot be set. The diff corresponding to this is:
--------------------------------------------------------------------------------------------
diff --git a/drivers/usb/cdns3/cdns3-gadget.c b/drivers/usb/cdns3/cdns3-gadget.c
index fd1beb10bba7..67d8b0805ba0 100644
--- a/drivers/usb/cdns3/cdns3-gadget.c
+++ b/drivers/usb/cdns3/cdns3-gadget.c
@@ -2935,10 +2935,24 @@ static int cdns3_gadget_pullup(struct usb_gadget *gadget, int is_on)
return 0;
}
-static void cdns3_gadget_config(struct cdns3_device *priv_dev)
+static int cdns3_gadget_config(struct cdns3_device *priv_dev)
{
struct cdns3_usb_regs __iomem *regs = priv_dev->regs;
u32 reg;
+ int ret;
+
+ /* keep Fast Access bit */
+ writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
+ reg = readl(&priv_dev->regs->usb_pwr);
+ if (!(reg & PUSB_PWR_FST_REG_ACCESS_STAT)) {
+ ret = readl_poll_timeout_atomic(&priv_dev->regs->usb_pwr, reg,
+ (reg & PUSB_PWR_FST_REG_ACCESS_STAT),
+ 10, 1000);
+ if (ret) {
+ dev_err(priv_dev->dev, "enabling fast access timed out\n");
+ return ret;
+ }
+ }
cdns3_ep0_config(priv_dev);
@@ -2971,10 +2985,10 @@ static void cdns3_gadget_config(struct cdns3_device *priv_dev)
/* enable generic interrupt*/
writel(USB_IEN_INIT, ®s->usb_ien);
writel(USB_CONF_CLK2OFFDS | USB_CONF_L1DS, ®s->usb_conf);
- /* keep Fast Access bit */
- writel(PUSB_PWR_FST_REG_ACCESS, &priv_dev->regs->usb_pwr);
cdns3_configure_dmult(priv_dev, NULL);
+
+ return 0;
}
/**
@@ -2990,10 +3004,15 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
struct cdns3_device *priv_dev = gadget_to_cdns3_device(gadget);
unsigned long flags;
enum usb_device_speed max_speed = driver->max_speed;
+ int ret;
spin_lock_irqsave(&priv_dev->lock, flags);
priv_dev->gadget_driver = driver;
+ ret = cdns3_gadget_config(priv_dev);
+ if (ret)
+ return ret;
+
/* limit speed if necessary */
max_speed = min(driver->max_speed, gadget->max_speed);
@@ -3018,7 +3037,6 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
break;
}
- cdns3_gadget_config(priv_dev);
spin_unlock_irqrestore(&priv_dev->lock, flags);
return 0;
}
@@ -3471,11 +3489,15 @@ __must_hold(&cdns->lock)
static int cdns3_gadget_resume(struct cdns *cdns, bool hibernated)
{
struct cdns3_device *priv_dev = cdns->gadget_dev;
+ int ret;
if (!priv_dev->gadget_driver)
return 0;
- cdns3_gadget_config(priv_dev);
+ ret = cdns3_gadget_config(priv_dev);
+ if (ret)
+ return ret;
+
if (hibernated)
writel(USB_CONF_DEVEN, &priv_dev->regs->usb_conf);
--------------------------------------------------------------------------------------------
Regards,
Siddharth.
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