Re: [PATCH 2/2] arm: use swiotlb for bounce buffer on LPAE configs

Robin Murphy
2020-01-08T12:21:30Z

On 08/01/2020 8:28 am, Peter Ujfalusi via iommu wrote:
> Hi Christoph,
>
> On 19/12/2019 17.20, Peter Ujfalusi wrote:
>> Hi Christoph,
>>
>> On 19/12/2019 17.02, Christoph Hellwig wrote:
>>> Hi Peter,
>>>
>>> can you try the patch below (it will need to be split into two):
>>
>> Thank you!
>>
>> Unfortunately it does not help:
>> [ 0.596208] edma: probe of 2700000.edma failed with error -5
>> [ 0.596626] edma: probe of 2728000.edma failed with error -5
>> ...
>> [ 2.108602] sdhci-omap 23000000.mmc: Got CD GPIO
>> [ 2.113899] mmc0: Failed to set 32-bit DMA mask.
>> [ 2.118592] mmc0: No suitable DMA available - falling back to PIO
>> [ 2.159038] mmc0: SDHCI controller on 23000000.mmc [23000000.mmc]
>> using PIO
>> [ 2.167531] mmc1: Failed to set 32-bit DMA mask.
>> [ 2.172192] mmc1: No suitable DMA available - falling back to PIO
>> [ 2.213841] mmc1: SDHCI controller on 23100000.mmc [23100000.mmc]
>> using PIO
>
> Do you have idea on how to fix this in a proper way?
>
> IMHO when drivers are setting the dma_mask and coherent_mask the
> dma_pfn_offset should not be applied to the mask at all.
>
> If I understand it correctly for EDMA as example:
>
> I set dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));
> since it can only address memory in this range.
>
> It does not matter if dma_pfn_offset is 0 or not 0 (like in k2g, where
> it is 0x780000) the EDMA still can only address within 32 bits.
>
> The dma_pfn_offset will tell us that the memory location's physical
> address is seen by the DMA at (phys_pfn - dma_pfn_offset) -> dma_pfn.
>
> The dma_mask should be checked against the dma_pfn.

That's exactly what dma_direct_supported() does, though. What it doesn't
do, AFAICS, is account for weird cases where the DMA zone *starts* way,
way above 32 physical address bits because of an implicit assumption
that *all* devices have a dma_pfn_offset equal to min_low_pfn. I'm not
sure how possible it is to cope with that generically.

Robin.

> We can not 'move' the dma_mask with dma_pfn_offset when setting the mask
> since it is not correct. The DMA can access in 32 bits range and we have
> the peripherals under 0x8000 0000.
>
> I might be missing something, but it looks to me that the way we set the
> dma_mask and the coherent_mask is the place where this can be fixed.
>
> Best regards,
> - Péter
>
>>
>> - Péter
>>
>>
>>> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
>>> index e822af0d9219..30b9c6786ce3 100644
>>> --- a/arch/arm/mm/dma-mapping.c
>>> +++ b/arch/arm/mm/dma-mapping.c
>>> @@ -221,7 +221,8 @@ EXPORT_SYMBOL(arm_coherent_dma_ops);
>>>
>>> static int __dma_supported(struct device *dev, u64 mask, bool warn)
>>> {
>>> - unsigned long max_dma_pfn = min(max_pfn, arm_dma_pfn_limit);
>>> + unsigned long max_dma_pfn =
>>> + min_t(unsigned long, max_pfn, zone_dma_limit >> PAGE_SHIFT);
>>>
>>> /*
>>> * Translate the device's DMA mask to a PFN limit. This
>>> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
>>> index 3ef204137e73..dd0e169a1bb1 100644
>>> --- a/arch/arm/mm/init.c
>>> +++ b/arch/arm/mm/init.c
>>> @@ -19,6 +19,7 @@
>>> #include <linux/gfp.h>
>>> #include <linux/memblock.h>
>>> #include <linux/dma-contiguous.h>
>>> +#include <linux/dma-direct.h>
>>> #include <linux/sizes.h>
>>> #include <linux/stop_machine.h>
>>> #include <linux/swiotlb.h>
>>> @@ -84,15 +85,6 @@ static void __init find_limits(unsigned long *min, unsigned long *max_low,
>>> phys_addr_t arm_dma_zone_size __read_mostly;
>>> EXPORT_SYMBOL(arm_dma_zone_size);
>>>
>>> -/*
>>> - * The DMA mask corresponding to the maximum bus address allocatable
>>> - * using GFP_DMA. The default here places no restriction on DMA
>>> - * allocations. This must be the smallest DMA mask in the system,
>>> - * so a successful GFP_DMA allocation will always satisfy this.
>>> - */
>>> -phys_addr_t arm_dma_limit;
>>> -unsigned long arm_dma_pfn_limit;
>>> -
>>> static void __init arm_adjust_dma_zone(unsigned long *size, unsigned long *hole,
>>> unsigned long dma_size)
>>> {
>>> @@ -108,14 +100,14 @@ static void __init arm_adjust_dma_zone(unsigned long *size, unsigned long *hole,
>>>
>>> void __init setup_dma_zone(const struct machine_desc *mdesc)
>>> {
>>> -#ifdef CONFIG_ZONE_DMA
>>> - if (mdesc->dma_zone_size) {
>>> + if (!IS_ENABLED(CONFIG_ZONE_DMA)) {
>>> + zone_dma_limit = ((phys_addr_t)~0);
>>> + } else if (mdesc->dma_zone_size) {
>>> arm_dma_zone_size = mdesc->dma_zone_size;
>>> - arm_dma_limit = PHYS_OFFSET + arm_dma_zone_size - 1;
>>> - } else
>>> - arm_dma_limit = 0xffffffff;
>>> - arm_dma_pfn_limit = arm_dma_limit >> PAGE_SHIFT;
>>> -#endif
>>> + zone_dma_limit = PHYS_OFFSET + arm_dma_zone_size - 1;
>>> + } else {
>>> + zone_dma_limit = 0xffffffff;
>>> + }
>>> }
>>>
>>> static void __init zone_sizes_init(unsigned long min, unsigned long max_low,
>>> @@ -279,7 +271,7 @@ void __init arm_memblock_init(const struct machine_desc *mdesc)
>>> early_init_fdt_scan_reserved_mem();
>>>
>>> /* reserve memory for DMA contiguous allocations */
>>> - dma_contiguous_reserve(arm_dma_limit);
>>> + dma_contiguous_reserve(zone_dma_limit);
>>>
>>> arm_memblock_steal_permitted = false;
>>> memblock_dump_all();
>>> diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
>>> index 88c121ac14b3..7dbd77554273 100644
>>> --- a/arch/arm/mm/mm.h
>>> +++ b/arch/arm/mm/mm.h
>>> @@ -82,14 +82,6 @@ extern __init void add_static_vm_early(struct static_vm *svm);
>>>
>>> #endif
>>>
>>> -#ifdef CONFIG_ZONE_DMA
>>> -extern phys_addr_t arm_dma_limit;
>>> -extern unsigned long arm_dma_pfn_limit;
>>> -#else
>>> -#define arm_dma_limit ((phys_addr_t)~0)
>>> -#define arm_dma_pfn_limit (~0ul >> PAGE_SHIFT)
>>> -#endif
>>> -
>>> extern phys_addr_t arm_lowmem_limit;
>>>
>>> void __init bootmem_init(void);
>>> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
>>> index b65dffdfb201..7a7501acd763 100644
>>> --- a/arch/arm64/mm/init.c
>>> +++ b/arch/arm64/mm/init.c
>>> @@ -441,7 +441,7 @@ void __init arm64_memblock_init(void)
>>> early_init_fdt_scan_reserved_mem();
>>>
>>> if (IS_ENABLED(CONFIG_ZONE_DMA)) {
>>> - zone_dma_bits = ARM64_ZONE_DMA_BITS;
>>> + zone_dma_limit = DMA_BIT_MASK(ARM64_ZONE_DMA_BITS);
>>> arm64_dma_phys_limit = max_zone_phys(ARM64_ZONE_DMA_BITS);
>>> }
>>>
>>> diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
>>> index 9488b63dfc87..337ace03d3f0 100644
>>> --- a/arch/powerpc/mm/mem.c
>>> +++ b/arch/powerpc/mm/mem.c
>>> @@ -223,7 +223,7 @@ static int __init mark_nonram_nosave(void)
>>> * everything else. GFP_DMA32 page allocations automatically fall back to
>>> * ZONE_DMA.
>>> *
>>> - * By using 31-bit unconditionally, we can exploit zone_dma_bits to inform the
>>> + * By using 31-bit unconditionally, we can exploit zone_dma_limit to inform the
>>> * generic DMA mapping code. 32-bit only devices (if not handled by an IOMMU
>>> * anyway) will take a first dip into ZONE_NORMAL and get otherwise served by
>>> * ZONE_DMA.
>>> @@ -257,18 +257,20 @@ void __init paging_init(void)
>>> printk(KERN_DEBUG "Memory hole size: %ldMB\n",
>>> (long int)((top_of_ram - total_ram) >> 20));
>>>
>>> +#ifdef CONFIG_ZONE_DMA
>>> /*
>>> * Allow 30-bit DMA for very limited Broadcom wifi chips on many
>>> * powerbooks.
>>> */
>>> - if (IS_ENABLED(CONFIG_PPC32))
>>> - zone_dma_bits = 30;
>>> - else
>>> - zone_dma_bits = 31;
>>> -
>>> -#ifdef CONFIG_ZONE_DMA
>>> - max_zone_pfns[ZONE_DMA] = min(max_low_pfn,
>>> - 1UL << (zone_dma_bits - PAGE_SHIFT));
>>> + if (IS_ENABLED(CONFIG_PPC32)) {
>>> + zone_dma_limit = DMA_BIT_MASK(30);
>>> + max_zone_pfns[ZONE_DMA] = min(max_low_pfn,
>>> + 1UL << (30 - PAGE_SHIFT));
>>> + } else {
>>> + zone_dma_limit = DMA_BIT_MASK(31);
>>> + max_zone_pfns[ZONE_DMA] = min(max_low_pfn,
>>> + 1UL << (31 - PAGE_SHIFT));
>>> + }
>>> #endif
>>> max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
>>> #ifdef CONFIG_HIGHMEM
>>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>>> index f0ce22220565..c403f61cb56b 100644
>>> --- a/arch/s390/mm/init.c
>>> +++ b/arch/s390/mm/init.c
>>> @@ -118,7 +118,7 @@ void __init paging_init(void)
>>>
>>> sparse_memory_present_with_active_regions(MAX_NUMNODES);
>>> sparse_init();
>>> - zone_dma_bits = 31;
>>> + zone_dma_limit = DMA_BIT_MASK(31);
>>> memset(max_zone_pfns, 0, sizeof(max_zone_pfns));
>>> max_zone_pfns[ZONE_DMA] = PFN_DOWN(MAX_DMA_ADDRESS);
>>> max_zone_pfns[ZONE_NORMAL] = max_low_pfn;
>>> diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
>>> index 24b8684aa21d..20d56d597506 100644
>>> --- a/include/linux/dma-direct.h
>>> +++ b/include/linux/dma-direct.h
>>> @@ -6,7 +6,7 @@
>>> #include <linux/memblock.h> /* for min_low_pfn */
>>> #include <linux/mem_encrypt.h>
>>>
>>> -extern unsigned int zone_dma_bits;
>>> +extern phys_addr_t zone_dma_limit;
>>>
>>> #ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
>>> #include <asm/dma-direct.h>
>>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>>> index 6af7ae83c4ad..5ea1bed2ba6f 100644
>>> --- a/kernel/dma/direct.c
>>> +++ b/kernel/dma/direct.c
>>> @@ -21,7 +21,7 @@
>>> * it for entirely different regions. In that case the arch code needs to
>>> * override the variable below for dma-direct to work properly.
>>> */
>>> -unsigned int zone_dma_bits __ro_after_init = 24;
>>> +phys_addr_t zone_dma_limit __ro_after_init = DMA_BIT_MASK(24);
>>>
>>> static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
>>> {
>>> @@ -74,7 +74,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
>>> * Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
>>> * zones.
>>> */
>>> - if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
>>> + if (*phys_limit <= zone_dma_limit)
>>> return GFP_DMA;
>>> if (*phys_limit <= DMA_BIT_MASK(32))
>>> return GFP_DMA32;
>>> @@ -483,7 +483,7 @@ int dma_direct_supported(struct device *dev, u64 mask)
>>> u64 min_mask;
>>>
>>> if (IS_ENABLED(CONFIG_ZONE_DMA))
>>> - min_mask = DMA_BIT_MASK(zone_dma_bits);
>>> + min_mask = zone_dma_limit;
>>> else
>>> min_mask = DMA_BIT_MASK(32);
>>>
>>>
>>> _______________________________________________
>>> linux-arm-kernel mailing list
>>> linux-arm-kernel@lists.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>>
>>
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>>
>
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