Sarah Sharp wrote:
> On Tue, Jun 08, 2010 at 10:07:47AM +0200, Clemens Ladisch wrote:
> > Sarah Sharp wrote:
> > > If so, it might be useful to introduce a new HCD driver function to
> > > enable MSI, which the USB core can call in usb_add_hcd(). The hosts
> > > could have a flag to indicate whether they are designed to handle
> > > MSI/MSI-X.
> >
> > Instead of a flag in struct hc_driver, we'd need another callback to be
> > able to do the per-device whitelisting checks.
>
> Where do you propose the callback be used? In usb_add_hcd() or
> somewhere else, like pci-quirks.c?
A whitelist (which would require disabling MSI for all HCDs except
those in the list) doesn't feel right for pci-quirks.c.
Okay, the callback would look something like below. (Implementation
of the callback for EHCI is in the second mail.)
The interrupt number and flags for usb_add_hcd() are determined in
usb_hcd_pci_probe(), so this is where the new code ends up.
MSI is just a minor variation of a normal interrupt, but this design
cannot handle MSI-X as it isn't known how many interrupts are acceptable,
or what the dev parameters in the request_irq() calls should be.
It appears that common MSI code is easy, but that implementing MSI-X
still requires replacing most of the generic hcd interrupt handling code
(either with a callback or by replacing the interrupt later).
---8<-------------------------------------------------------------->8---
USB: allow PCI controllers to use message-signaled interrupts
This patch adds the capability to use MSI to the PCI HCD framework.
To avoid problems with broken chips that have never been tested with
MSI, the HCD driver must explicitly consent before enabling MSI is
attempted.
NOT-yet-signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
---
include/linux/usb/hcd.h | 3 +++
drivers/usb/core/hcd-pci.c | 10 +++++++++-
2 files changed, 12 insertions(+), 1 deletion(-)
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -190,6 +190,9 @@ struct hc_driver {
#define HCD_USB3 0x0040 /* USB 3.0 */
#define HCD_MASK 0x0070
+ /* determines if hcd-pci should try to enable MSI */
+ bool (*is_pci_msi_allowed) (struct usb_hcd *hcd);
+
/* called to init HCD and root hub */
int (*reset) (struct usb_hcd *hcd);
int (*start) (struct usb_hcd *hcd);
--- a/drivers/usb/core/hcd-pci.c
+++ b/drivers/usb/core/hcd-pci.c
@@ -176,6 +176,7 @@ int usb_hcd_pci_probe(struct pci_dev *de
{
struct hc_driver *driver;
struct usb_hcd *hcd;
+ unsigned long irqflags;
int retval;
if (usb_disabled())
@@ -246,13 +247,19 @@ int usb_hcd_pci_probe(struct pci_dev *de
pci_set_master(dev);
- retval = usb_add_hcd(hcd, dev->irq, IRQF_DISABLED | IRQF_SHARED);
+ irqflags = IRQF_DISABLED | IRQF_SHARED;
+ if (driver->is_pci_msi_allowed && driver->is_pci_msi_allowed(hcd))
+ if (pci_enable_msi(dev) == 0)
+ irqflags &= ~IRQF_SHARED;
+
+ retval = usb_add_hcd(hcd, dev->irq, irqflags);
if (retval != 0)
goto err4;
set_hs_companion(dev, hcd);
return retval;
err4:
+ pci_disable_msi(dev);
if (driver->flags & HCD_MEMORY) {
iounmap(hcd->regs);
err3:
@@ -293,6 +300,7 @@ void usb_hcd_pci_remove(struct pci_dev *
return;
usb_remove_hcd(hcd);
+ pci_disable_msi(dev);
if (hcd->driver->flags & HCD_MEMORY) {
iounmap(hcd->regs);
release_mem_region(hcd->rsrc_start, hcd->rsrc_len);
--
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