linux-kernel - Re: [PATCH 2/4] usb: dwc3: dwc3-omap: return -EPROBE

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Message-ID: <20130305152156.GK12123@arwen.pp.htv.fi>
Date:	Tue, 5 Mar 2013 17:21:56 +0200
From:	Felipe Balbi <balbi@...com>
To:	kishon <kishon@...com>
CC:	<balbi@...com>, <grant.likely@...retlab.ca>,
	<rob.herring@...xeda.com>, <rob@...dley.net>,
	<gregkh@...uxfoundation.org>, <s-guiriec@...com>,
	<gg@...mlogic.co.uk>, <sameo@...ux.intel.com>,
	<broonie@...nsource.wolfsonmicro.com>, <ldewangan@...dia.com>,
	<devicetree-discuss@...ts.ozlabs.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [PATCH 2/4] usb: dwc3: dwc3-omap: return -EPROBE_DEFER if probe
 has not yet executed

On Tue, Mar 05, 2013 at 08:48:24PM +0530, kishon wrote:
> Hi,
> 
> On Tuesday 05 March 2013 08:36 PM, Felipe Balbi wrote:
> >On Tue, Mar 05, 2013 at 08:31:58PM +0530, kishon wrote:
> >>Hi,
> >>
> >>On Tuesday 05 March 2013 08:26 PM, Felipe Balbi wrote:
> >>>On Tue, Mar 05, 2013 at 07:51:58PM +0530, Kishon Vijay Abraham I wrote:
> >>>>return -EPROBE_DEFER from dwc3_omap_mailbox in dwc3-omap.c, if the probe of
> >>>>dwc3-omap has not yet been executed or failed.
> >>>>
> >>>>Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
> >>>>---
> >>>>  drivers/usb/dwc3/dwc3-omap.c  |    7 +++++--
> >>>>  include/linux/usb/dwc3-omap.h |    6 +++---
> >>>>  2 files changed, 8 insertions(+), 5 deletions(-)
> >>>>
> >>>>diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
> >>>>index 19c6e72..9428f4e 100644
> >>>>--- a/drivers/usb/dwc3/dwc3-omap.c
> >>>>+++ b/drivers/usb/dwc3/dwc3-omap.c
> >>>>@@ -138,11 +138,14 @@ static inline void dwc3_omap_writel(void __iomem *base, u32 offset, u32 value)
> >>>>  	writel(value, base + offset);
> >>>>  }
> >>>>
> >>>>-void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
> >>>>+int dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
> >>>>  {
> >>>>  	u32			val;
> >>>>  	struct dwc3_omap	*omap = _omap;
> >>>>
> >>>>+	if (!omap)
> >>>>+		return -EPROBE_DEFER;
> >>>>+
> >>>>  	switch (status) {
> >>>>  	case OMAP_DWC3_ID_GROUND:
> >>>>  		dev_dbg(omap->dev, "ID GND\n");
> >>>>@@ -185,7 +188,7 @@ void dwc3_omap_mailbox(enum omap_dwc3_vbus_id_status status)
> >>>>  		dev_dbg(omap->dev, "ID float\n");
> >>>>  	}
> >>>>
> >>>>-	return;
> >>>>+	return IRQ_HANDLED;
> >>>
> >>>IRQ_HANDLED ????
> >>
> >>Actually I did it that way since palmas_vbus_wakeup_irq can directly
> >>return the return value from dwc3_omap_mailbox. If this seems hacky
> >>to you, I'll change it.
> >
> >it does seem hacky :-) Try something like:
> >
> >ret = dwc3_omap_mailbox();
> >if (ret)
> >	print_error();
> >
> >return IRQ_HANDLED;
> 
> hmm.. But there is one case where palmas_vbus_wakeup_irq should
> return EPROBE_DEFER. In the cold plug case, if palmas gets loaded
> before dwc3-omap, omap in dwc3_omap_mailbox will be NULL. So ideally
> palmas should be probed after dwc3-omap for this case. Returning
> IRQ_HANDLED or IRQ_NONE wont help here.

you can return IRQ_HANDLED but don't clear the IRQ status bits, which
will make the IRQ retrigger, right ?

If you return -EPROBE_DEFER from within the IRQ handler, what will
happen ? IRQ subsystem only understands IRQ_NONE, IRQ_WAKE_THREAD, and
IRQ_HANDLED. How do you suppose it will treat -EPROBE_DEFER ?

-- 
balbi

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