linux-kernel - Re: [PATCH v7 1/5] usb: dwc3: omap: use request_threaded

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Date:	Wed, 11 May 2016 16:52:34 +0300
From:	Roger Quadros <rogerq@...com>
To:	Felipe Balbi <balbi@...nel.org>
CC:	<tony@...mide.com>, <Joao.Pinto@...opsys.com>,
	<sergei.shtylyov@...entembedded.com>, <peter.chen@...escale.com>,
	<jun.li@...escale.com>, <grygorii.strashko@...com>,
	<yoshihiro.shimoda.uh@...esas.com>, <nsekhar@...com>,
	<b-liu@...com>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 1/5] usb: dwc3: omap: use request_threaded_irq()

On 11/05/16 15:39, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
>>>>> static irqreturn_t dwc3_omap_threaded_interrupt(int irq, void *_omap)
>>>>> {
>>>>>         struct dwc3_omap *omap = _omap;
>>>>>         u32 reg;
>>>>>
>>>>>         spin_lock(&omap->lock);
>>>>
>>>> Do we really need a spin_lock for the dwc3-omap driver?
>>>> Currently we won't be doing anything other than just
>>>> clearing the irqstatus and re-enabling the interrupts.
>>>
>>> well, if there's no possibility of races, then no. But only testing will
>>> say for sure, I guess. I didn't really go through the entire thing just
>>> to a write a quick little template :-p
>>>
>> OK. Another hurdle I have is that how do I mask/unmask the interrupts?
>> I do not see any masking bits, only enable/disable bits.
>>
>> I don't think we can use the enable/disable bits to mask as we'd loose
>> events while the event is disabled.
> 
> I'm pretty sure your TRM discusses the usage of IRQSTATUS_RAW*
> registers, doesn't it ? :-)

It does and also says that it is mostly for debug. But I don't mind using it
if it solves our problem :).

> 
> Those registers should be modified by HW even when interrupts are
> disabled/masked. Note that, the IRQSTATUS_SET* and IRQSTATUS_CLR*
> registers act more like mask/unmask than enable/disable considering we
> can still read IRQ status using *RAW* registers.
> 
> See if below works fine for OMAP5, AM4 and AM5 SoCs:
> 
> diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
> index af264493bbae..ece2f25ad2c3 100644
> --- a/drivers/usb/dwc3/dwc3-omap.c
> +++ b/drivers/usb/dwc3/dwc3-omap.c
> @@ -165,20 +165,20 @@ static void dwc3_omap_write_utmi_ctrl(struct dwc3_omap *omap, u32 value)
>  
>  static u32 dwc3_omap_read_irq0_status(struct dwc3_omap *omap)
>  {
> -	return dwc3_omap_readl(omap->base, USBOTGSS_IRQSTATUS_0 -
> +	return dwc3_omap_readl(omap->base, USBOTGSS_IRQSTATUS_RAW_0 -
>  						omap->irq0_offset);
>  }
>  
>  static void dwc3_omap_write_irq0_status(struct dwc3_omap *omap, u32 value)
>  {
> -	dwc3_omap_writel(omap->base, USBOTGSS_IRQSTATUS_0 -
> +	dwc3_omap_writel(omap->base, USBOTGSS_IRQSTATUS_RAW_0 -
>  						omap->irq0_offset, value);

We shouldn't write to RAW here as it will trigger a software IRQ instead of
clearing the event.
>  
>  }
>  
>  static u32 dwc3_omap_read_irqmisc_status(struct dwc3_omap *omap)
>  {
> -	return dwc3_omap_readl(omap->base, USBOTGSS_IRQSTATUS_MISC +
> +	return dwc3_omap_readl(omap->base, USBOTGSS_IRQSTATUS_RAW_MISC +
>  						omap->irqmisc_offset);
>  }
>  
> 

The rest is fine. It seemed to work on omap5. I'll do more tests though.
Thanks for the hint :)

cheers,
-roger