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);
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