On 23/08/2017 17:43, Will Deacon wrote:
On Wed, Aug 23, 2017 at 03:29:46PM +0100, John Garry wrote:
On 23/08/2017 14:24, Will Deacon wrote:
On Wed, Aug 23, 2017 at 02:17:24PM +0100, John Garry wrote:
Signed-off-by: Shameer Kolothum
<shameerali.kolothum.thodi@xxxxxxxxxx>
---
drivers/iommu/arm-smmu-v3.c | 27 ++++++++++++++++++++++-----
1 file changed, 22 insertions(+), 5 deletions(-)
Please can you also add a devicetree binding with corresponding
documentation to enable this workaround on non-ACPI based systems too?
It should be straightforward if you update the arm_smmu_options table.
As I mentioned before, devicetree was a lower priority and we would definitely
submit patch to support that. Even if we update the arm_smmu_options table
with DT binding, the generic function to retrieve the MSI address regions only
works on ACPI/IORT case now.
Hi Will,
Can you confirm your stance on supporting this workaround for DT as well as
ACPI?
For us, we now only "officially" support ACPI FW, and DT support at this
point is patchy/limited. To me, adding DT support is just more errata
workaround code to maintain with little useful gain.
I basically don't like the idea of a driver that only works for one of
ACPI or DT yet claims to support both. I'm less fussed about functionality
differences (feature X is only available with firmware Y), but not working
around a hardware erratum that we know about is just lazy.
So I'd prefer that we handle this in both cases, or blacklist affected
devices when booting with DT. Continuing as though there isn't an erratum
is the worst thing we can do.
OK, seems reasonable.
We would consider blacklisting the device, where/how to do is the question.
So the errata is in the GICv3 ITS/PCI host controller, and we just use the
in-between SMMU (driver) to provide the workaround. So my initial impression
is that the PCI host controller would have to be blacklisted IFF behind an
IOMMU for DT firmware in pcie-hisi.c or pci quirks framework. How does it
sound?
If that avoids us running into the erratum, then fine by me. I'd obviously
prefer we work-around it since we know how to, but that's up to you.
I'm surpsised that you may want more errata workaround code to maintain.
Anyway we'll check both approaches and show you how they look and go
from there.
Please also note that in our SoC we have other devices behind the same SMMU,
like storage controller, which are not affected or related to the Errata.
BTW, ignoring DT support, are you happy with this patchset?
Yes, but I won't ack it without the above taken care of.
Fair enough.
Will
Thanks,
John
.
--
To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
