RE: [PATCH v9 5/6] usb:cdns3 Add Cadence USB3 DRD Driver

[Felipe Balbi]

Hi,

Pawel Laszczak <pawell@xxxxxxxxxxx> writes:
>>> +void cdns3_role_stop(struct cdns3 *cdns)
>>
>>not static? Why is it so that _start() is static but _stop() is not?
>>Looks fishy
>
> This function is used in cdns3_role_stop in debugfs.c file so it can't
> be static.

it's still super fishy. Why don't you need _start() from debugfs.c? In
any case, the role framework would remove the need for any of this, I
suppose.

>>> +static int cdns3_idle_role_start(struct cdns3 *cnds)
>>> +{	/* Hold PHY in RESET */
>>
>>huh?
>>
>>> +	return 0;
>>> +}
>>> +
>>> +static void cdns3_idle_role_stop(struct cdns3 *cnds)
>>> +{
>>> +	/* Program Lane swap and bring PHY out of RESET */
>>
>>double huh?
>>
>
> These functions were added for consistency with FSM described in controller specification. 
> Yes, I know that you don't like empty functions :), but it could be helpful in
> understanding how this controller work.

frankly, it really doesn't. An empty function doesn't really help IMHO.

>>> +static const char *const cdns3_mode[] = {
>>> +	[USB_DR_MODE_UNKNOWN]		= "unknown",
>>> +	[USB_DR_MODE_OTG]		= "otg",
>>> +	[USB_DR_MODE_HOST]		= "host",
>>> +	[USB_DR_MODE_PERIPHERAL]	= "device",
>>> +};
>>
>>don't we have a generic version of this under usb/common ?
>>
> Yes, there is a similar array, but it is defined also as static 
> and there is no function for converting value to string. 
> There is only function for converting string to value.

right. You can add the missing interface generically instead of
duplicating the enumeration.

> There is also:  
> [USB_DR_MODE_UNKNOWN]		= "",
> Instead of: 
> [USB_DR_MODE_UNKNOWN]		= "unknown",
>
> So, for USB_DR_MODE_UNKNOWN user will not see anything information.

But that's what "unknown" means :-) We don't know the information.

>>> +static irqreturn_t cdns3_drd_irq(int irq, void *data)
>>> +{
>>> +	irqreturn_t ret = IRQ_NONE;
>>> +	struct cdns3 *cdns = data;
>>> +	u32 reg;
>>> +
>>> +	if (cdns->dr_mode != USB_DR_MODE_OTG)
>>> +		return ret;
>>> +
>>> +	reg = readl(&cdns->otg_regs->ivect);
>>> +
>>> +	if (!reg)
>>> +		return ret;
>>> +
>>> +	if (reg & OTGIEN_ID_CHANGE_INT) {
>>> +		dev_dbg(cdns->dev, "OTG IRQ: new ID: %d\n",
>>> +			cdns3_get_id(cdns));
>>> +
>>> +		ret = IRQ_HANDLED;
>>> +	}
>>> +
>>> +	if (reg & (OTGIEN_VBUSVALID_RISE_INT | OTGIEN_VBUSVALID_FALL_INT)) {
>>> +		dev_dbg(cdns->dev, "OTG IRQ: new VBUS: %d\n",
>>> +			cdns3_get_vbus(cdns));
>>> +
>>> +		ret = IRQ_HANDLED;
>>> +	}
>>> +
>>> +	if (ret == IRQ_HANDLED)
>>> +		queue_work(system_freezable_wq, &cdns->role_switch_wq);
>>> +
>>> +	writel(~0, &cdns->otg_regs->ivect);
>>> +	return ret;
>>> +}
>>
>>seems like you could use threaded irq to avoid this workqueue.
>
>
> This function is also called in cdns3_mode_write (debugfs.c file),
> therefor after changing it to threaded irq I will still need workqueue. 

Why? debugfs writes are not atomic. They run in process context, right?
Just don't disable interrupts while running this and you should be fine.

>>> +	cdns->desired_dr_mode = cdns->dr_mode;
>>> +	cdns->current_dr_mode = USB_DR_MODE_UNKNOWN;
>>> +
>>> +	ret = devm_request_threaded_irq(cdns->dev, cdns->otg_irq,
>>> +					cdns3_drd_irq,
>>> +					NULL, IRQF_SHARED,
>>
>>if you don't have a threaded handler, you should set IRQF_ONESHOT. I
>>would prefer if you implement a threaded handler that doesn't require
>>IRQF_ONESHOT, though.
>>
>
> IRQF_ONESHOT can be used  only in threaded handled. 
> "
>  * IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
>  *                Used by threaded interrupts which need to keep the
>  *                irq line disabled until the threaded handler has been run.
> "

so?

>>> +	} else {
>>> +		struct usb_request *request;
>>> +
>>> +		if (priv_dev->eps[index]->flags & EP_WEDGE) {
>>> +			cdns3_select_ep(priv_dev, 0x00);
>>> +			return 0;
>>> +		}
>>> +
>>> +		cdns3_dbg(priv_ep->cdns3_dev, "Clear Stalled endpoint %s\n",
>>> +			  priv_ep->name);
>>
>>why do you need your own wrapper around dev_dbg()? This looks quite unnecessary.
>
> It's generic function used for adding message to trace.log.  It's not wrapper to dev_dbg 
>
> void cdns3_dbg(struct cdns3_device *priv_dev, const char *fmt, ...)
> {
> 	struct va_format vaf;
> 	va_list args;
>
> 	va_start(args, fmt);
> 	vaf.fmt = fmt;
> 	vaf.va = &args;
> 	trace_cdns3_log(priv_dev, &vaf);
> 	va_end(args);
> }

oh. Don't do it like that. Add a proper trace event that actually
decodes the information you want. These random messages will give you
trouble in the future. I had this sort of construct in dwc3 for a while
and it became clear that it's a bad idea. It's best to have trace events
that decode information coming from the HW. That way your trace logs
have a "predictable" shape/format and you can easily find problem areas.

-- 
balbi

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