On Sat, Oct 10, 2020 at 10:12 AM Nicolas Saenz Julienne
<nsaenzjulienne@xxxxxxx> wrote:
>
> The function provides the CPU physical address addressable by the most
> constrained bus in the system. It might be useful in order to
> dynamically set up memory zones during boot.
>
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> ---
> drivers/of/address.c | 34 ++++++++++++++++++++++++++++++++++
> include/linux/of.h | 7 +++++++
> 2 files changed, 41 insertions(+)
>
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index eb9ab4f1e80b..755e97b65096 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -1024,6 +1024,40 @@ int of_dma_get_range(struct device_node *np, const struct bus_dma_region **map)
> }
> #endif /* CONFIG_HAS_DMA */
>
> +/**
> + * of_dma_safe_phys_limit - Get system wide DMA safe address space
> + *
> + * Gets the CPU physical address limit for safe DMA addressing system wide by
> + * searching for the most constraining dma-range. Otherwise it returns ~0ULL.
> + */
> +u64 __init of_dma_safe_phys_limit(void)
> +{
> + struct device_node *np = NULL;
> + struct of_range_parser parser;
> + const __be32 *ranges = NULL;
> + u64 phys_dma_limit = ~0ULL;
> + struct of_range range;
> + int len;
> +
> + for_each_of_allnodes(np) {
> + dma_addr_t cpu_end = 0;
> +
> + ranges = of_get_property(np, "dma-ranges", &len);
> + if (!ranges || !len)
> + continue;
> +
> + of_dma_range_parser_init(&parser, np);
> + for_each_of_range(&parser, &range)
> + if (range.cpu_addr + range.size > cpu_end)
> + cpu_end = range.cpu_addr + range.size;
This doesn't work if you have more than one level of dma-ranges. The
address has to be translated first. It should be okay to do that on
the start or end address (if not, your DT is broken).
Please add/extend a unittest for this.
> +
> + if (phys_dma_limit > cpu_end)
> + phys_dma_limit = cpu_end;
> + }
> +
> + return phys_dma_limit;
> +}
> +
> /**
> * of_dma_is_coherent - Check if device is coherent
> * @np: device node
> diff --git a/include/linux/of.h b/include/linux/of.h
> index 481ec0467285..958c64cffa92 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -558,6 +558,8 @@ int of_map_id(struct device_node *np, u32 id,
> const char *map_name, const char *map_mask_name,
> struct device_node **target, u32 *id_out);
>
> +u64 of_dma_safe_phys_limit(void);
> +
> #else /* CONFIG_OF */
>
> static inline void of_core_init(void)
> @@ -995,6 +997,11 @@ static inline int of_map_id(struct device_node *np, u32 id,
> return -EINVAL;
> }
>
> +static inline u64 of_dma_safe_phys_limit(void)
> +{
> + return ~0ULL;
> +}
> +
> #define of_match_ptr(_ptr) NULL
> #define of_match_node(_matches, _node) NULL
> #endif /* CONFIG_OF */
> --
> 2.28.0
>
