On 6/10/20 9:19 AM, Vladimir Murzin wrote:
> On 6/10/20 8:24 AM, Christoph Hellwig wrote:
>> Ok, I finally found the original patch from Vladimir. Comments below:
>>
>>> +++ 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));;
>>
>> I think we should try to reuse the mmu dma_direct_mmap implementation,
>> which does about the same. This version has been compile tested on
>> arm-nommu only, let me know what you think: (btw, a nommu_defconfig of
>> some kind for arm would be nice..)
>
> Catch-all nommu_defconfig is not easy for ARM, AFAIK folk carry few hacks
> for randconfig...
>
> Meanwhile, known working NOMMU configs
>
> $ git grep "# CONFIG_MMU is not set" arch/arm/configs/
> arch/arm/configs/efm32_defconfig:# CONFIG_MMU is not set
> arch/arm/configs/lpc18xx_defconfig:# CONFIG_MMU is not set
> arch/arm/configs/mps2_defconfig:# CONFIG_MMU is not set
> arch/arm/configs/stm32_defconfig:# CONFIG_MMU is not set
> arch/arm/configs/vf610m4_defconfig:# CONFIG_MMU is not set
>
>>
>> diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
>> index d006668c0027d2..e0dae570a51530 100644
>> --- a/kernel/dma/Kconfig
>> +++ b/kernel/dma/Kconfig
>> @@ -71,6 +71,7 @@ config SWIOTLB
>> # in the pagetables
>> #
>> config DMA_NONCOHERENT_MMAP
>> + default y if !MMU
>> bool
>
> Nit: def_bool !MMU
>
>>
>> config DMA_REMAP
>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>> index 0a4881e59aa7d6..9ec6a5c3fc578c 100644
>> --- a/kernel/dma/direct.c
>> +++ b/kernel/dma/direct.c
>> @@ -459,7 +459,6 @@ int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,
>> return ret;
>> }
>>
>> -#ifdef CONFIG_MMU
>> bool dma_direct_can_mmap(struct device *dev)
>> {
>> return dev_is_dma_coherent(dev) ||
>> @@ -485,19 +484,6 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
>> return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
>> user_count << PAGE_SHIFT, vma->vm_page_prot);
>> }
>> -#else /* CONFIG_MMU */
>> -bool dma_direct_can_mmap(struct device *dev)
>> -{
>> - return false;
>> -}
>> -
>> -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;
>> -}
>> -#endif /* CONFIG_MMU */
>>
>> int dma_direct_supported(struct device *dev, u64 mask)
>> {
>>
>
> LGTM. FWIW:
>
> Reviewed-by: Vladimir Murzin <vladimir.murzin@xxxxxxx>
>
>
@dillon, can you give it a try?
I think Christoph would appreciate your Tested-by and that might speed up
getting fix mainline.
Cheers
Vladimir
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