Re: [PATCH v2 01/10] iommu/ipmmu-vmsa: Refactor micro-TLB lookup

Laurent Pinchart
2014-07-10T10:37:57Z

On Thursday 10 July 2014 09:03:26 Khiem Nguyen wrote:
> On 5/15/2014 7:40 PM, Laurent Pinchart wrote:
> > Cache the micro-TLB number in archdata allocated in the .add_device
> > handler instead of looking it up when the deviced is attached and
> > detached. This simplifies the .attach_dev and .detach_dev operations and
> > prepares for DT support.
>
> [snip]
>
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
>
> [snip]
>
> > +static int ipmmu_find_utlb(struct ipmmu_vmsa_device *mmu, struct device
> > *dev)
> > +{
> > + const struct ipmmu_vmsa_master *master = mmu->pdata->masters;
> > + const char *devname = dev_name(dev);
> > + unsigned int i;
> > +
> > + for (i = 0; i < mmu->pdata->num_masters; ++i, ++master) {
> > + if (strcmp(master->name, devname) == 0)
> > + return master->utlb;
> > + }
> > +
> > + return -1;
> > +}
>
> [snip]
>
> > static int ipmmu_add_device(struct device *dev)
>
> [snip]
>
> > list_for_each_entry(mmu, &ipmmu_devices, list) {
> > - master = ipmmu_find_master(mmu, dev);
> > - if (master) {
> > + utlb = ipmmu_find_utlb(mmu, dev);
> > + if (utlb >= 0) {
> > /*
> > - * TODO Take a reference to the master to protect
> > + * TODO Take a reference to the MMU to protect
> > * against device removal.
> > */
> > break;
>
> [snip]
>
> > + archdata->mmu = mmu;
> > + archdata->utlb = utlb;
>
> [snip]
>
> I have one question for ipmmu_add_device().
>
> In my understanding, your code will find utlb for device
> base on device name.
> For any device, it will /only/ return utlb number of first match.
>
> How about the case that a device name connected with more than 1 utlb ?
> e.g DU device (rcar-du-r8a7790) in Lager
>
> Was that case already covered in your code ?

For the DU case, the R8A7790 contains two DU devices, each connected to a
single utlb. The IPMMU driver will thus work fine in that case.

I agree that this is a problem in general though, other devices (such as the
DMAC) are connected to more than one utlb. This is currently not supported by
the driver.

--
Regards,

Laurent Pinchart