On Tue, Sep 05, 2023 at 12:34:58PM +0100, Marc Zyngier wrote:
> On Tue, 05 Sep 2023 11:47:21 +0100,
> Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx> wrote:
> >
> > The GIC architecture specification defines a set of registers
> > for redistributors and ITSes that control the sharebility and
> > cacheability attributes of redistributors/ITSes initiator ports
> > on the interconnect (GICR_[V]PROPBASER, GICR_[V]PENDBASER,
> > GITS_BASER<n>).
> >
> > Architecturally the GIC provides a means to drive shareability
> > and cacheability attributes signals and related IWB/OWB/ISH barriers
> > but it is not mandatory for designs to wire up the corresponding
> > interconnect signals that control the cacheability/shareability
> > of transactions.
> >
> > Redistributors and ITSes interconnect ports can be connected to
> > non-coherent interconnects that are not able to manage the
> > shareability/cacheability attributes; this implicitly makes
> > the redistributors and ITSes non-coherent observers.
> >
> > So far, the GIC driver on probe executes a write to "probe" for
> > the redistributors and ITSes registers shareability bitfields
> > by writing a value (ie InnerShareable - the shareability domain the
> > CPUs are in) and check it back to detect whether the value sticks or
> > not; this hinges on a GIC programming model behaviour that predates the
> > current specifications, that just define shareability bits as writeable
> > but do not guarantee that writing certain shareability values
> > enable the expected behaviour for the redistributors/ITSes
> > memory interconnect ports.
> >
> > To enable non-coherent GIC designs, introduce the "dma-noncoherent"
> > device tree property to allow firmware to describe redistributors and
> > ITSes as non-coherent observers on the memory interconnect and use the
> > property to force the shareability attributes to be programmed into the
> > redistributors and ITSes registers.
> >
> > Signed-off-by: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
> > Cc: Robin Murphy <robin.murphy@xxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Marc Zyngier <maz@xxxxxxxxxx>
> > ---
> > drivers/irqchip/irq-gic-v3-its.c | 19 +++++++++++++++----
> > 1 file changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> > index e0c2b10d154d..758ea3092305 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -5056,7 +5056,8 @@ static int __init its_compute_its_list_map(struct resource *res,
> > }
> >
> > static int __init its_probe_one(struct resource *res,
> > - struct fwnode_handle *handle, int numa_node)
> > + struct fwnode_handle *handle, int numa_node,
> > + bool non_coherent)
> > {
> > struct its_node *its;
> > void __iomem *its_base;
> > @@ -5148,7 +5149,7 @@ static int __init its_probe_one(struct resource *res,
> > gits_write_cbaser(baser, its->base + GITS_CBASER);
> > tmp = gits_read_cbaser(its->base + GITS_CBASER);
> >
> > - if (its->flags & ITS_FLAGS_FORCE_NON_SHAREABLE)
> > + if (its->flags & ITS_FLAGS_FORCE_NON_SHAREABLE || non_coherent)
> > tmp &= ~GITS_CBASER_SHAREABILITY_MASK;
>
> Please use the non_coherent attribute to set the flag, instead of
> using it as some sideband signalling. Not having this information
> stored in the its_node structure makes it harder to debug.
>
> We have an over-engineered quirk framework, and it should be put to a
> good use.
That makes sense, I will do - I was wondering though whether this
is a quirk or a binding that describes the architecture because
the architecture can't provide that information.
That's the reason why I have not implemented it as a quirk but
obviously that's exactly the feedback I need.
>
> >
> > if ((tmp ^ baser) & GITS_CBASER_SHAREABILITY_MASK) {
> > @@ -5356,11 +5357,19 @@ static const struct of_device_id its_device_id[] = {
> > {},
> > };
> >
> > +static void of_check_rdists_coherent(struct device_node *node)
> > +{
> > + if (of_property_read_bool(node, "dma-noncoherent"))
> > + gic_rdists->flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
> > +}
> > +
> > static int __init its_of_probe(struct device_node *node)
> > {
> > struct device_node *np;
> > struct resource res;
> >
> > + of_check_rdists_coherent(node);
>
> It really feels that the flag should instead be communicated by the
> base GIC driver, as it readily communicates the whole rdists structure
> already.
Yes I had the same feeling while writing the code but the patch
below (if we treat this as quirk) is already much cleaner.
> > +
> > /*
> > * Make sure *all* the ITS are reset before we probe any, as
> > * they may be sharing memory. If any of the ITS fails to
> > @@ -5396,7 +5405,8 @@ static int __init its_of_probe(struct device_node *node)
> > continue;
> > }
> >
> > - its_probe_one(&res, &np->fwnode, of_node_to_nid(np));
> > + its_probe_one(&res, &np->fwnode, of_node_to_nid(np),
> > + of_property_read_bool(np, "dma-noncoherent"));
> > }
> > return 0;
> > }
> > @@ -5533,7 +5543,8 @@ static int __init gic_acpi_parse_madt_its(union acpi_subtable_headers *header,
> > }
> >
> > err = its_probe_one(&res, dom_handle,
> > - acpi_get_its_numa_node(its_entry->translation_id));
> > + acpi_get_its_numa_node(its_entry->translation_id),
> > + false);
>
> I came up with the following alternative approach, which is as usual
> completely untested. It is entirely based on the quirk infrastructure,
> and doesn't touch the ACPI path at all.
The patch below makes sense and it is much cleaner - provided we
consider this a quirk, which I am not sure it is, that's the only
question I have.
Thanks,
Lorenzo
> Thanks,
>
> M.
>
> diff --git a/drivers/irqchip/irq-gic-common.h b/drivers/irqchip/irq-gic-common.h
> index 3db4592cda1c..00641e88aa38 100644
> --- a/drivers/irqchip/irq-gic-common.h
> +++ b/drivers/irqchip/irq-gic-common.h
> @@ -29,4 +29,8 @@ void gic_enable_quirks(u32 iidr, const struct gic_quirk *quirks,
> void gic_enable_of_quirks(const struct device_node *np,
> const struct gic_quirk *quirks, void *data);
>
> +#define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING (1 << 0)
> +#define RDIST_FLAGS_RD_TABLES_PREALLOCATED (1 << 1)
> +#define RDIST_FLAGS_FORCE_NON_SHAREABLE (1 << 2)
> +
> #endif /* _IRQ_GIC_COMMON_H */
> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> index e0c2b10d154d..6edf59af757b 100644
> --- a/drivers/irqchip/irq-gic-v3-its.c
> +++ b/drivers/irqchip/irq-gic-v3-its.c
> @@ -44,10 +44,6 @@
> #define ITS_FLAGS_WORKAROUND_CAVIUM_23144 (1ULL << 2)
> #define ITS_FLAGS_FORCE_NON_SHAREABLE (1ULL << 3)
>
> -#define RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING (1 << 0)
> -#define RDIST_FLAGS_RD_TABLES_PREALLOCATED (1 << 1)
> -#define RDIST_FLAGS_FORCE_NON_SHAREABLE (1 << 2)
> -
> #define RD_LOCAL_LPI_ENABLED BIT(0)
> #define RD_LOCAL_PENDTABLE_PREALLOCATED BIT(1)
> #define RD_LOCAL_MEMRESERVE_DONE BIT(2)
> @@ -4754,6 +4750,14 @@ static bool __maybe_unused its_enable_rk3588001(void *data)
> return true;
> }
>
> +static bool its_set_non_coherent(void *data)
> +{
> + struct its_node *its = data;
> +
> + its->flags |= ITS_FLAGS_FORCE_NON_SHAREABLE;
> + return true;
> +}
> +
> static const struct gic_quirk its_quirks[] = {
> #ifdef CONFIG_CAVIUM_ERRATUM_22375
> {
> @@ -4808,6 +4812,11 @@ static const struct gic_quirk its_quirks[] = {
> .init = its_enable_rk3588001,
> },
> #endif
> + {
> + .desc = "ITS: non-coherent attribute",
> + .property = "dma-noncoherent",
> + .init = its_set_non_coherent,
> + },
> {
> }
> };
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index eedfa8e9f077..7f518c0ae723 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -1857,6 +1857,14 @@ static bool gic_enable_quirk_arm64_2941627(void *data)
> return true;
> }
>
> +static bool rd_set_non_coherent(void *data)
> +{
> + struct gic_chip_data *d = data;
> +
> + d->rdists.flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
> + return true;
> +}
> +
> static const struct gic_quirk gic_quirks[] = {
> {
> .desc = "GICv3: Qualcomm MSM8996 broken firmware",
> @@ -1923,6 +1931,11 @@ static const struct gic_quirk gic_quirks[] = {
> .mask = 0xff0f0fff,
> .init = gic_enable_quirk_arm64_2941627,
> },
> + {
> + .desc = "GICv3: non-coherent attribute",
> + .property = "dma-noncoherent",
> + .init = rd_set_non_coherent,
> + },
> {
> }
> };
>
> --
> Without deviation from the norm, progress is not possible.
>
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