On Wed, Sep 06, 2023 at 01:23:30PM +0200, Lorenzo Pieralisi wrote: > On Wed, Sep 06, 2023 at 10:52:01AM +0100, Marc Zyngier wrote: > > On 2023-09-06 10:41, Lorenzo Pieralisi wrote: > > > This series is v2 of a previous version[1]. > > > > > > v1 -> v2: > > > - Updated DT bindings as per feedback > > > - Updated patch[2] to use GIC quirks infrastructure > > > > > > [1] > > > https://lore.kernel.org/all/20230905104721.52199-1-lpieralisi@xxxxxxxxxx > > > > > > Original cover letter > > > --- > > > The GICv3 architecture specifications provide a means for the > > > system programmer to set the shareability and cacheability > > > attributes the GIC components (redistributors and ITSes) use > > > to drive memory transactions. > > > > > > Albeit the architecture give control over shareability/cacheability > > > memory transactions attributes (and barriers), it is allowed to > > > connect the GIC interconnect ports to non-coherent memory ports > > > on the interconnect, basically tying off shareability/cacheability > > > "wires" and de-facto making the redistributors and ITSes non-coherent > > > memory observers. > > > > > > This series aims at starting a discussion over a possible solution > > > to this problem, by adding to the GIC device tree bindings the > > > standard dma-noncoherent property. The GIC driver uses the property > > > to force the redistributors and ITSes shareability attributes to > > > non-shareable, which consequently forces the driver to use CMOs > > > on GIC memory tables. > > > > > > On ARM DT DMA is default non-coherent, so the GIC driver can't rely > > > on the generic DT dma-coherent/non-coherent property management layer > > > (of_dma_is_coherent()) which would default all GIC designs in the field > > > as non-coherent; it has to rely on ad-hoc dma-noncoherent property > > > handling. > > > > > > When a consistent approach is agreed upon for DT an equivalent binding > > > will > > > be put forward for ACPI based systems. > > > > What is the plan for this last point? I'd like to see at least > > a proposal before taking this series in. > > Absolutely, I am starting a thread on related MADT changes, should not > take too long. Quick update, bindings filed, I will code against it but we should not merge anything till it is approved (could be missing v6.7 timeline). https://bugzilla.tianocore.org/show_bug.cgi?id=4557 Lorenzo
