On 6/8/20 9:30 AM, dillon.minfei@xxxxxxxxx wrote:
> From: dillon min <dillon.minfei@xxxxxxxxx>
>
> Currently, we use dma direct to request coherent memory for driver on armv7m
> platform if 'cacheid' is zero, but dma_direct_can_mmap() is return false,
> dma_direct_mmap() return -ENXIO for CONFIG_MMU undefined platform.
>
> so we have to back to use 'arm_nommu_dma_ops', add use_reserved_mem() to check
> if device support global or device corherent memory. if yes, then call
> set_dma_ops()
>
> Signed-off-by: dillon min <dillon.minfei@xxxxxxxxx>
> ---
> arch/arm/mm/dma-mapping-nommu.c | 28 +++++++++++++++++++++++++++-
> 1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/dma-mapping-nommu.c b/arch/arm/mm/dma-mapping-nommu.c
> index 287ef898a55e..e1c213fec152 100644
> --- a/arch/arm/mm/dma-mapping-nommu.c
> +++ b/arch/arm/mm/dma-mapping-nommu.c
> @@ -14,6 +14,7 @@
> #include <asm/cacheflush.h>
> #include <asm/outercache.h>
> #include <asm/cp15.h>
> +#include <linux/of.h>
>
> #include "dma.h"
>
> @@ -188,6 +189,31 @@ const struct dma_map_ops arm_nommu_dma_ops = {
> };
> EXPORT_SYMBOL(arm_nommu_dma_ops);
>
> +static bool use_reserved_mem(struct device *dev)
> +{
> + struct device_node *np;
> +
> + np = of_find_node_by_path("/reserved-memory/linux,dma");
> +
> + if (np &&
> + of_device_is_compatible(np, "shared-dma-pool") &&
> + of_property_read_bool(np, "no-map") &&
> + of_property_read_bool(np, "linux,dma-default")) {
> + /* has global corherent mem support */
> + of_node_put(np);
> + return true;
> + }
> +
> + np = of_parse_phandle(dev->of_node, "memory-region", 0);
> + if (np) {
> + /* has dev corherent mem support */
> + of_node_put(np);
> + return true;
> + }
> +
> + return false;
> +}
> +
> void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> const struct iommu_ops *iommu, bool coherent)
> {
> @@ -206,6 +232,6 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> dev->archdata.dma_coherent = (get_cr() & CR_M) ? coherent : true;
> }
>
> - if (!dev->archdata.dma_coherent)
> + if (!dev->archdata.dma_coherent || use_reserved_mem(dev))
> set_dma_ops(dev, &arm_nommu_dma_ops);
> }
>
Sorry I have to NAK this hack :(
Digging git history reveled 79964a1c2972 ("ARM: 8633/1: nommu: allow mmap when !CONFIG_MMU")
which make me wonder if diff below does the trick for you
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 8f4bbda..8623b9e 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -456,14 +456,14 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
#else /* CONFIG_MMU */
bool dma_direct_can_mmap(struct device *dev)
{
- return false;
+ return true;
}
int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
void *cpu_addr, dma_addr_t dma_addr, size_t size,
unsigned long attrs)
{
- return -ENXIO;
+ return vm_iomap_memory(vma, vma->vm_start, (vma->vm_end - vma->vm_start));;
}
#endif /* CONFIG_MMU */
Cheers
Vladimir
