[PATCH v3 1/7] swiotlb: make io_tlb_default_mem local to swiotlb.c

[Petr Tesarik <petrtesarik@xxxxxxxxxxxxxxx>]

From: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx>

SWIOTLB implementation details should not be exposed to the rest of the
kernel. This will allow to make changes to the implementation without
modifying non-swiotlb code.

To avoid breaking existing users, provide helper functions for the few
required fields. Enhance is_swiotlb_active() to work with the default IO
TLB pool when passed a NULL device.

As a bonus, using a helper function to initialize struct device allows to
get rid of an #ifdef in driver core.

Signed-off-by: Petr Tesarik <petr.tesarik.ext@xxxxxxxxxx>
---
 arch/arm/xen/mm.c          |  2 +-
 arch/mips/pci/pci-octeon.c |  2 +-
 arch/x86/kernel/pci-dma.c  |  2 +-
 drivers/base/core.c        |  4 +---
 drivers/xen/swiotlb-xen.c  |  2 +-
 include/linux/swiotlb.h    | 17 ++++++++++++++++-
 kernel/dma/swiotlb.c       | 39 ++++++++++++++++++++++++++++++++++++--
 7 files changed, 58 insertions(+), 10 deletions(-)

diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index 3d826c0b5fee..529aabc1be38 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -125,7 +125,7 @@ static int __init xen_mm_init(void)
                return 0;
 
        /* we can work with the default swiotlb */
-       if (!io_tlb_default_mem.nslabs) {
+       if (!is_swiotlb_active(NULL)) {
                rc = swiotlb_init_late(swiotlb_size_or_default(),
                                       xen_swiotlb_gfp(), NULL);
                if (rc < 0)
diff --git a/arch/mips/pci/pci-octeon.c b/arch/mips/pci/pci-octeon.c
index e457a18cbdc5..c5c4c1f7d5e4 100644
--- a/arch/mips/pci/pci-octeon.c
+++ b/arch/mips/pci/pci-octeon.c
@@ -664,7 +664,7 @@ static int __init octeon_pci_setup(void)
 
                /* BAR1 movable regions contiguous to cover the swiotlb */
                octeon_bar1_pci_phys =
-                       io_tlb_default_mem.start & ~((1ull << 22) - 1);
+                       default_swiotlb_start() & ~((1ull << 22) - 1);
 
                for (index = 0; index < 32; index++) {
                        union cvmx_pci_bar1_indexx bar1_index;
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de6be0a3965e..33e960672837 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -90,7 +90,7 @@ int pci_xen_swiotlb_init_late(void)
                return 0;
 
        /* we can work with the default swiotlb */
-       if (!io_tlb_default_mem.nslabs) {
+       if (!is_swiotlb_active(NULL)) {
                int rc = swiotlb_init_late(swiotlb_size_or_default(),
                                           GFP_KERNEL, xen_swiotlb_fixup);
                if (rc < 0)
diff --git a/drivers/base/core.c b/drivers/base/core.c
index 3dff5037943e..46d1d78c5beb 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -3108,9 +3108,7 @@ void device_initialize(struct device *dev)
     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
        dev->dma_coherent = dma_default_coherent;
 #endif
-#ifdef CONFIG_SWIOTLB
-       dev->dma_io_tlb_mem = &io_tlb_default_mem;
-#endif
+       swiotlb_dev_init(dev);
 }
 EXPORT_SYMBOL_GPL(device_initialize);
 
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 67aa74d20162..946bd56f0ac5 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -381,7 +381,7 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct 
scatterlist *sgl,
 static int
 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
 {
-       return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
+       return xen_phys_to_dma(hwdev, default_swiotlb_limit()) <= mask;
 }
 
 const struct dma_map_ops xen_swiotlb_dma_ops = {
diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 7af2673b47ba..b38045be532d 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -112,7 +112,6 @@ struct io_tlb_mem {
        atomic_long_t used_hiwater;
 #endif
 };
-extern struct io_tlb_mem io_tlb_default_mem;
 
 static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
 {
@@ -130,13 +129,19 @@ static inline bool is_swiotlb_force_bounce(struct device 
*dev)
 
 void swiotlb_init(bool addressing_limited, unsigned int flags);
 void __init swiotlb_exit(void);
+void swiotlb_dev_init(struct device *dev);
 size_t swiotlb_max_mapping_size(struct device *dev);
 bool is_swiotlb_active(struct device *dev);
 void __init swiotlb_adjust_size(unsigned long size);
+phys_addr_t default_swiotlb_start(void);
+phys_addr_t default_swiotlb_limit(void);
 #else
 static inline void swiotlb_init(bool addressing_limited, unsigned int flags)
 {
 }
+static inline void swiotlb_dev_init(struct device *dev)
+{
+}
 static inline bool is_swiotlb_buffer(struct device *dev, phys_addr_t paddr)
 {
        return false;
@@ -161,6 +166,16 @@ static inline bool is_swiotlb_active(struct device *dev)
 static inline void swiotlb_adjust_size(unsigned long size)
 {
 }
+
+static inline phys_addr_t default_swiotlb_start(void)
+{
+       return 0;
+}
+
+static inline phys_addr_t default_swiotlb_limit(void)
+{
+       return 0;
+}
 #endif /* CONFIG_SWIOTLB */
 
 extern void swiotlb_print_info(void);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 079df5ad38d0..63d318059f27 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -71,7 +71,7 @@ struct io_tlb_slot {
 static bool swiotlb_force_bounce;
 static bool swiotlb_force_disable;
 
-struct io_tlb_mem io_tlb_default_mem;
+static struct io_tlb_mem io_tlb_default_mem;
 
 static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
 static unsigned long default_nareas;
@@ -486,6 +486,15 @@ void __init swiotlb_exit(void)
        memset(mem, 0, sizeof(*mem));
 }
 
+/**
+ * swiotlb_dev_init() - initialize swiotlb fields in &struct device
+ * @dev:       Device to be initialized.
+ */
+void swiotlb_dev_init(struct device *dev)
+{
+       dev->dma_io_tlb_mem = &io_tlb_default_mem;
+}
+
 /*
  * Return the offset into a iotlb slot required to keep the device happy.
  */
@@ -939,14 +948,40 @@ size_t swiotlb_max_mapping_size(struct device *dev)
        return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE - min_align;
 }
 
+/**
+ * is_swiotlb_active() - check if the software IO TLB is initialized
+ * @dev:       Device to check, or %NULL for the default IO TLB.
+ */
 bool is_swiotlb_active(struct device *dev)
 {
-       struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
+       struct io_tlb_mem *mem = dev
+               ? dev->dma_io_tlb_mem
+               : &io_tlb_default_mem;
 
        return mem && mem->nslabs;
 }
 EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
+/**
+ * default_swiotlb_start() - get the start of the default SWIOTLB
+ *
+ * Get the lowest physical address used by the default software IO TLB pool.
+ */
+phys_addr_t default_swiotlb_start(void)
+{
+       return io_tlb_default_mem.start;
+}
+
+/**
+ * default_swiotlb_limit() - get the highest address in the default SWIOTLB
+ *
+ * Get the highest physical address used by the default software IO TLB pool.
+ */
+phys_addr_t default_swiotlb_limit(void)
+{
+       return io_tlb_default_mem.end - 1;
+}
+
 #ifdef CONFIG_DEBUG_FS
 
 static int io_tlb_used_get(void *data, u64 *val)
-- 
2.25.1