[PATCH 1/2] irqchip/gicv3-its: Support share device ID

[Minghuan.Lian at freescale.com]

Hi Marc,

Please see my comments inline

> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier at arm.com]
> Sent: Thursday, April 16, 2015 12:37 AM
> To: Lian Minghuan-B31939
> Cc: linux-pci at vger.kernel.org; Arnd Bergmann; Hu Mingkai-B21284; Zang
> Roy-R61911; Yoder Stuart-B08248; Bjorn Helgaas; Wood Scott-B07421; linux-
> arm-kernel at lists.infradead.org; Jason Cooper; Thomas Gleixner
> Subject: Re: [PATCH 1/2] irqchip/gicv3-its: Support share device ID
> 
> On Wed, 15 Apr 2015 17:49:23 +0800
> Minghuan Lian <Minghuan.Lian at freescale.com> wrote:
> 
> > SMMU of some platforms can only isolate limited device ID.
> > This may require that all PCI devices share the same ITS device with
> > the fixed device ID. The patch adds function
> > arch_msi_share_devid_update used for these platforms to update the
> > fixed device ID and maximum MSI interrupts number.
> >
> > Signed-off-by: Minghuan Lian <Minghuan.Lian at freescale.com>
> > ---
> >  drivers/irqchip/irq-gic-v3-its.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c
> > b/drivers/irqchip/irq-gic-v3-its.c
> > index d0374a6..be78d0a 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -1169,6 +1169,15 @@ static int its_get_pci_alias(struct pci_dev *pdev,
> u16 alias, void *data)
> >  	return 0;
> >  }
> >
> > +void __weak
> > +arch_msi_share_devid_update(struct pci_dev *pdev, u32 *dev_id, u32
> > +*nvesc) {
> > +	/*
> > +	 * use PCI_DEVID NOT share device ID as default
> > +	 * so nothing need to do
> > +	 */
> > +}
> > +
> 
> NAK. On top of being ugly as sin, this breaks any form of multiplatform
> support. No way anything like this is going in. Guys, you really should know
> better.
> 
[Minghuan]  The current ITS MSI will create an individual ITS device for each PCIe device, and use PCI_DEVID as ITS dev_id
However, out platform only supports  ITS dev_id 0 -63.  A normal PCIe DEVID of 0000:01:00.0 is 256 bigger than 63.
Besides, because of the limited dev_id number, all the PCIe device will share the same ITS dev. Our platform provides a hardware module LUT to map PCI DEVID to ITS dev_id.  So, when creating ITS device, we need to update dev_id and the nvesc.
I may change pci_for_each_dma_alias to add a new flag to use alias_bus and alias_devfn. 
But I also need to update nvesc which should contains all the PCI device MSI/MSIX nvesc and PCIe PME, aerdrv interrupts.
The main difference is that we need a ITS device to service multiple PCIe devices.
Could you give me some suggestions how to implement this requirement.
     

> >  static int its_msi_prepare(struct irq_domain *domain, struct device *dev,
> >  			   int nvec, msi_alloc_info_t *info)  { @@ -1185,6
> +1194,8 @@
> > static int its_msi_prepare(struct irq_domain *domain, struct device *dev,
> >  	dev_alias.count = nvec;
> >
> >  	pci_for_each_dma_alias(pdev, its_get_pci_alias, &dev_alias);
> > +	arch_msi_share_devid_update(pdev, &dev_alias.dev_id,
> > +&dev_alias.count);
> > +
> 
> See the function above? That's where the aliasing should be taken care of.
> 
[Minghuan] The alias will use dma_alias_devfn, but it does not contains alias_bus.
I need to translate PCI_DEVID to a fixed ID.

> >  	its = domain->parent->host_data;
> >
> >  	its_dev = its_find_device(its, dev_alias.dev_id);
> 
> Thanks,
> 
> 	M.
> --
> Jazz is not dead. It just smells funny.