linux-kernel - Re: [PATCH] usb/core: skip unnecessary line IRQ request for USB3

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Date:	Fri, 16 Mar 2012 16:05:54 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	gregkh <gregkh@...uxfoundation.org>, sarah.a.sharp@...ux.intel.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-usb <linux-usb@...r.kernel.org>
Subject: Re: [PATCH] usb/core: skip unnecessary line IRQ request for USB3

On Thu, 2012-03-15 at 22:39 +0800, Alex Shi wrote:
> > 
> > This is not a good idea.  What happens if some USB-3 controller 
> > (perhaps a non-xHCI USB-3 controller) doesn't use MSI?
> > 
> 
> 
> current usb3 driver just xhci. but sure it need to modify if non-xhci
> usb pops up.
> 
> > The right way to avoid registering a legacy interrupt handler is to 
> > call usb_add_hcd() with irqnum equal to 0.
> 
> 
> a good trick! will try it tomorrow.

Do you mean the following patch? It tested. :) 
------------
>>From 5ae9a6fe88752495af6da6182cad26620f1ab190 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@...el.com>
Date: Thu, 15 Mar 2012 08:12:47 +0800
Subject: [PATCH] usb/core: skip unnecessary line IRQ request for USB3

USB3(only xhci driver) requests line IRQ here but will disable it
in later driver->start function and try MSI first:

xhci_hcd 0000:02:00.0: irq 18, io mem 0xfe500000
xhci_hcd 0000:02:00.0: irq 45 for MSI/MSI-X
xhci_hcd 0000:02:00.0: irq 46 for MSI/MSI-X

So it is better to remove the redundant request here.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 drivers/usb/core/hcd-pci.c |    5 ++++-
 drivers/usb/host/xhci.c    |    3 ---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/hcd-pci.c b/drivers/usb/core/hcd-pci.c
index 81e2c0d..7b73c74 100644
--- a/drivers/usb/core/hcd-pci.c
+++ b/drivers/usb/core/hcd-pci.c
@@ -245,7 +245,10 @@ int usb_hcd_pci_probe(struct pci_dev *dev, const struct pci_device_id *id)
 
 	pci_set_master(dev);
 
-	retval = usb_add_hcd(hcd, dev->irq, IRQF_SHARED);
+	if ((driver->flags & HCD_MASK) != HCD_USB3)
+		retval = usb_add_hcd(hcd, dev->irq, IRQF_SHARED);
+	else
+		retval = usb_add_hcd(hcd, 0, IRQF_SHARED);
 	if (retval != 0)
 		goto unmap_registers;
 	set_hs_companion(dev, hcd);
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index c939f5f..64979c2 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -338,9 +338,6 @@ static int xhci_try_enable_msi(struct usb_hcd *hcd)
 	if (xhci->quirks & XHCI_BROKEN_MSI)
 		return 0;
 
-	/* unregister the legacy interrupt */
-	if (hcd->irq)
-		free_irq(hcd->irq, hcd);
 	hcd->irq = -1;
 
 	ret = xhci_setup_msix(xhci);
-- 
1.6.3.3



> 
> > 
> > Alan Stern
> > 
> 
> 
> 
> 


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