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

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

Robin,

On 08/01/2020 14.21, Robin Murphy wrote:
> 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.

Yes, this is my understanding as well.

> 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.

The problem - I think - is that the DMA_BIT_MASK(32) from
dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32)) is treated as physical
address along the call path so the dma_pfn_offset is applied to it and
the check will fail, saying that DMA_BIT_MASK(32) can not be supported.

Fyi, this is what I have gathered on k2g via prints:

dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32));

Prints inside dma_direct_supported():
sdhci-omap 23000000.mmc: max_pfn: 880000
sdhci-omap 23000000.mmc: min_mask #1: ffffff
sdhci-omap 23000000.mmc: min_mask #2: ffffff
sdhci-omap 23000000.mmc: dev->dma_pfn_offset: 780000
sdhci-omap 23000000.mmc: PAGE_SHIFT: 12
sdhci-omap 23000000.mmc: __phys_to_dma(dev, min_mask): ff880ffffff
sdhci-omap 23000000.mmc: mask: ffffffff

Print in dma_supported() after returning from dma_direct_supported():
sdhci-omap 23000000.mmc: dma_is_direct, ret = 0

sdhci-omap 23100000.mmc: DMA is not supported for the device

keystone-k2g have this in soc0 node:
dma-ranges = <0x80000000 0x8 0x00000000 0x80000000>;

DDR starts at 0x8 0000 0000 (8G) and 2G is aliased at 0x8000 0000.

This gives the 0x780000 for dma_pfn_offset for all devices underneath it.

The DMA_BIT_MASK(24) is passed to __phys_to_dma() because
CONFIG_ZONE_DMA is enabled.

SWIOTLB is enabled in kconfig.

> I'm not sure how possible it is to cope with that generically.

Me neither, but k2g is failing since v5.3-rc3 and the bisect pointed to
this commit.

> 
> 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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>>

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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