On Tue, 14 Sep 2021 14:54:07 +0100,
"Sven Peter" <sven@xxxxxxxxxxxxx> wrote:
>
>
>
> On Mon, Sep 13, 2021, at 20:25, Marc Zyngier wrote:
> > The MSI doorbell on Apple HW can be any address in the low 4GB
> > range. However, the MSI write is matched by the PCIe block before
> > hitting the iommu. It must thus be excluded from the IOVA range
> > that is assigned to any PCIe device.
> >
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
>
> It's not pretty but I'm not aware of any better solution and this should
> work as long as these two are always paired. With the small nit below
> addressed:
>
> Reviewed-by: Sven Peter <sven@xxxxxxxxxxxxx>
>
> > ---
> > drivers/iommu/apple-dart.c | 25 +++++++++++++++++++++++++
> > drivers/pci/controller/Kconfig | 5 +++++
> > drivers/pci/controller/pcie-apple.c | 4 +++-
> > 3 files changed, 33 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> > index 559db9259e65..d1456663688e 100644
> > --- a/drivers/iommu/apple-dart.c
> > +++ b/drivers/iommu/apple-dart.c
> > @@ -721,6 +721,29 @@ static int apple_dart_def_domain_type(struct device *dev)
> > return 0;
> > }
> >
> > +#define DOORBELL_ADDR (CONFIG_PCIE_APPLE_MSI_DOORBELL_ADDR & PAGE_MASK)
> > +
> > +static void apple_dart_get_resv_regions(struct device *dev,
> > + struct list_head *head)
> > +{
> > +#ifdef CONFIG_PCIE_APPLE
>
> I think using IS_ENABLED would be better here in case the pcie
> driver is built as a module which would then only define
> CONFIG_PCIE_APPLE_MODULE AIUI.
You're right, this isn't great. However, IS_ENABLED() still results in
the evaluation of the following code by the compiler, even if it would
be dropped by the optimiser.
I resorted to the following construct:
<quote>
#ifndef CONFIG_PCIE_APPLE_MSI_DOORBELL_ADDR
/* Keep things compiling when CONFIG_PCI_APPLE isn't selected */
#define CONFIG_PCIE_APPLE_MSI_DOORBELL_ADDR 0
#endif
#define DOORBELL_ADDR (CONFIG_PCIE_APPLE_MSI_DOORBELL_ADDR & PAGE_MASK)
static void apple_dart_get_resv_regions(struct device *dev,
struct list_head *head)
{
if (IS_ENABLED(CONFIG_PCIE_APPLE) && dev_is_pci(dev)) {
</quote>
which is ugly, but works. The alternative is, of course, to add a new
include file for one single value, which I find even worse.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
