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Subject: Re: [PATCH 2/2] arm: use swiotlb for bounce buffer on LPAE configs
From:   Peter Ujfalusi <peter.ujfalusi@ti.com>
To:     Christoph Hellwig <hch@lst.de>
CC:     Vignesh Raghavendra <vigneshr@ti.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Russell King - ARM Linux admin <linux@armlinux.org.uk>,
        <linux-kernel@vger.kernel.org>, <iommu@lists.linux-foundation.org>,
        <linux-arm-kernel@lists.infradead.org>,
        Roger Quadros <rogerq@ti.com>
References: <20190709142011.24984-1-hch@lst.de>
 <20190709142011.24984-3-hch@lst.de>
 <9bbd87c2-5b6c-069c-dd22-5105dc827428@ti.com> <20191219150259.GA3003@lst.de>
 <20106a84-8247-fa78-2381-2c94fad9cb6a@ti.com>
Message-ID: <eca457b6-c685-59ac-1dec-5b28e4430e1d@ti.com>
Date:   Wed, 8 Jan 2020 10:28:04 +0200
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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.

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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