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    SubjectRe: [PATCH v4 12/18] of/address: Add infrastructure to declare MMIO as non-posted
    On Fri, Apr 02, 2021 at 06:05:36PM +0900, Hector Martin wrote:
    > This implements the 'nonposted-mmio' boolean property. Placing this
    > property in a bus marks all direct child devices as requiring
    > non-posted MMIO mappings. If no such property is found, the default
    > is posted MMIO.
    >
    > of_mmio_is_nonposted() performs this check to determine if a given
    > device has requested non-posted MMIO.
    >
    > of_address_to_resource() uses this to set the IORESOURCE_MEM_NONPOSTED
    > flag on resources that require non-posted MMIO.
    >
    > of_iomap() and of_io_request_and_map() then use this flag to pick the
    > correct ioremap() variant.
    >
    > This mechanism is currently restricted to builds that support Apple ARM
    > platforms, as an optimization.
    >
    > Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
    > Signed-off-by: Hector Martin <marcan@marcan.st>
    > ---
    > drivers/of/address.c | 43 ++++++++++++++++++++++++++++++++++++--
    > include/linux/of_address.h | 1 +
    > 2 files changed, 42 insertions(+), 2 deletions(-)
    >
    > diff --git a/drivers/of/address.c b/drivers/of/address.c
    > index 73ddf2540f3f..6485cc536e81 100644
    > --- a/drivers/of/address.c
    > +++ b/drivers/of/address.c
    > @@ -847,6 +847,9 @@ static int __of_address_to_resource(struct device_node *dev,
    > return -EINVAL;
    > memset(r, 0, sizeof(struct resource));
    >
    > + if (of_mmio_is_nonposted(dev))
    > + flags |= IORESOURCE_MEM_NONPOSTED;
    > +
    > r->start = taddr;
    > r->end = taddr + size - 1;
    > r->flags = flags;
    > @@ -896,7 +899,10 @@ void __iomem *of_iomap(struct device_node *np, int index)
    > if (of_address_to_resource(np, index, &res))
    > return NULL;
    >
    > - return ioremap(res.start, resource_size(&res));
    > + if (res.flags & IORESOURCE_MEM_NONPOSTED)
    > + return ioremap_np(res.start, resource_size(&res));
    > + else
    > + return ioremap(res.start, resource_size(&res));
    > }
    > EXPORT_SYMBOL(of_iomap);
    >
    > @@ -928,7 +934,11 @@ void __iomem *of_io_request_and_map(struct device_node *np, int index,
    > if (!request_mem_region(res.start, resource_size(&res), name))
    > return IOMEM_ERR_PTR(-EBUSY);
    >
    > - mem = ioremap(res.start, resource_size(&res));
    > + if (res.flags & IORESOURCE_MEM_NONPOSTED)
    > + mem = ioremap_np(res.start, resource_size(&res));
    > + else
    > + mem = ioremap(res.start, resource_size(&res));
    > +
    > if (!mem) {
    > release_mem_region(res.start, resource_size(&res));
    > return IOMEM_ERR_PTR(-ENOMEM);
    > @@ -1094,3 +1104,32 @@ bool of_dma_is_coherent(struct device_node *np)
    > return false;
    > }
    > EXPORT_SYMBOL_GPL(of_dma_is_coherent);
    > +
    > +/**
    > + * of_mmio_is_nonposted - Check if device uses non-posted MMIO
    > + * @np: device node
    > + *
    > + * Returns true if the "nonposted-mmio" property was found for
    > + * the device's bus.
    > + *
    > + * This is currently only enabled on builds that support Apple ARM devices, as
    > + * an optimization.
    > + */
    > +bool of_mmio_is_nonposted(struct device_node *np)
    > +{
    > + struct device_node *parent;
    > + bool nonposted;
    > +
    > + if (!IS_ENABLED(CONFIG_ARCH_APPLE))
    > + return false;
    > +
    > + parent = of_get_parent(np);
    > + if (!parent)
    > + return false;
    > +
    > + nonposted = of_property_read_bool(parent, "nonposted-mmio");
    > +
    > + of_node_put(parent);
    > + return nonposted;
    > +}
    > +EXPORT_SYMBOL_GPL(of_mmio_is_nonposted);

    Is this needed outside of of/address.c? If not, please make it static
    and don't export.

    With that,

    Reviewed-by: Rob Herring <robh@kernel.org>

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