Date:   Wed, 8 Jan 2020 12:21:20 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>,
        Christoph Hellwig <hch@....de>
Cc:     Vignesh Raghavendra <vigneshr@...com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Russell King - ARM Linux admin <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, Roger Quadros <rogerq@...com>
Subject: Re: [PATCH 2/2] arm: use swiotlb for bounce buffer on LPAE configs

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@...ts.infradead.org
>>> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
>>>
>>
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>>
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>>
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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