Merge tag 'arc-4.19-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc

Pull ARC updates from Vineet Gupta:

 - Fix for atomic_fetch_#op  [Will Deacon]

 - Enable per device IOC [Eugeniy Paltsev]

 - Remove redundant gcc version checks [Masahiro Yamada]

 - Miscll platform config/DT updates [Alexey Brodkin]

* tag 'arc-4.19-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/vgupta/arc:
  ARC: don't check for HIGHMEM pages in arch_dma_alloc
  ARC: IOC: panic if both IOC and ZONE_HIGHMEM enabled
  ARC: dma [IOC] Enable per device io coherency
  ARC: dma [IOC]: mark DMA devices connected as dma-coherent
  ARC: atomics: unbork atomic_fetch_##op()
  arc: remove redundant GCC version checks
  ARC: sort Kconfig
  ARC: cleanup show_faulting_vma()
  ARC: [plat-axs*]: Enable SWAP
  ARC: [plat-axs*/plat-hsdk]: Allow U-Boot to pass MAC-address to the kernel
  ARC: configs: cleanup

arch/arc/Kconfig

@@ -9,6 +9,7 @@
 config ARC
 	def_bool y
 	select ARC_TIMERS
+	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select ARCH_HAS_SG_CHAIN
@@ -28,8 +29,12 @@ config ARC
 	select GENERIC_SMP_IDLE_THREAD
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
+	select HAVE_DEBUG_STACKOVERFLOW
 	select HAVE_FUTEX_CMPXCHG if FUTEX
+	select HAVE_GENERIC_DMA_COHERENT
 	select HAVE_IOREMAP_PROT
+	select HAVE_KERNEL_GZIP
+	select HAVE_KERNEL_LZMA
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
 	select HAVE_MEMBLOCK
@@ -44,11 +49,6 @@ config ARC
 	select OF_EARLY_FLATTREE
 	select OF_RESERVED_MEM
 	select PERF_USE_VMALLOC if ARC_CACHE_VIPT_ALIASING
-	select HAVE_DEBUG_STACKOVERFLOW
-	select HAVE_GENERIC_DMA_COHERENT
-	select HAVE_KERNEL_GZIP
-	select HAVE_KERNEL_LZMA
-	select ARCH_HAS_PTE_SPECIAL
 
 config ARCH_HAS_CACHE_LINE_SIZE
 	def_bool y

arch/arc/Makefile

@@ -43,10 +43,7 @@ ifdef CONFIG_ARC_CURR_IN_REG
 LINUXINCLUDE	+=  -include ${src}/arch/arc/include/asm/current.h
 endif
 
-upto_gcc44    :=  $(call cc-ifversion, -le, 0404, y)
-atleast_gcc44 :=  $(call cc-ifversion, -ge, 0404, y)
-
-cflags-$(atleast_gcc44)			+= -fsection-anchors
+cflags-y				+= -fsection-anchors
 
 cflags-$(CONFIG_ARC_HAS_LLSC)		+= -mlock
 cflags-$(CONFIG_ARC_HAS_SWAPE)		+= -mswape
@@ -82,11 +79,6 @@ cflags-$(disable_small_data)		+= -mno-sdata -fcall-used-gp
 cflags-$(CONFIG_CPU_BIG_ENDIAN)		+= -mbig-endian
 ldflags-$(CONFIG_CPU_BIG_ENDIAN)	+= -EB
 
-# STAR 9000518362: (fixed with binutils shipping with gcc 4.8)
-# arc-linux-uclibc-ld (buildroot) or arceb-elf32-ld (EZChip) don't accept
-# --build-id w/o "-marclinux". Default arc-elf32-ld is OK
-ldflags-$(upto_gcc44)			+= -marclinux
-
 LIBGCC	:= $(shell $(CC) $(cflags-y) --print-libgcc-file-name)
 
 # Modules with short calls might break for calls into builtin-kernel

arch/arc/boot/dts/axc003.dtsi

@@ -93,6 +93,32 @@ arcpct0: pct {
 		};
 	};
 
+	/*
+	 * Mark DMA peripherals connected via IOC port as dma-coherent. We do
+	 * it via overlay because peripherals defined in axs10x_mb.dtsi are
+	 * used for both AXS101 and AXS103 boards and only AXS103 has IOC (so
+	 * only AXS103 board has HW-coherent DMA peripherals)
+	 * We don't need to mark pgu@17000 as dma-coherent because it uses
+	 * external DMA buffer located outside of IOC aperture.
+	 */
+	axs10x_mb {
+		ethernet@0x18000 {
+			dma-coherent;
+		};
+
+		ehci@0x40000 {
+			dma-coherent;
+		};
+
+		ohci@0x60000 {
+			dma-coherent;
+		};
+
+		mmc@0x15000 {
+			dma-coherent;
+		};
+	};
+
 	/*
 	 * The DW APB ICTL intc on MB is connected to CPU intc via a
 	 * DT "invisible" DW APB GPIO block, configured to simply pass thru

arch/arc/boot/dts/axc003_idu.dtsi

@@ -100,6 +100,32 @@ arcpct0: pct {
 		};
 	};
 
+	/*
+	 * Mark DMA peripherals connected via IOC port as dma-coherent. We do
+	 * it via overlay because peripherals defined in axs10x_mb.dtsi are
+	 * used for both AXS101 and AXS103 boards and only AXS103 has IOC (so
+	 * only AXS103 board has HW-coherent DMA peripherals)
+	 * We don't need to mark pgu@17000 as dma-coherent because it uses
+	 * external DMA buffer located outside of IOC aperture.
+	 */
+	axs10x_mb {
+		ethernet@0x18000 {
+			dma-coherent;
+		};
+
+		ehci@0x40000 {
+			dma-coherent;
+		};
+
+		ohci@0x60000 {
+			dma-coherent;
+		};
+
+		mmc@0x15000 {
+			dma-coherent;
+		};
+	};
+
 	/*
 	 * This INTC is actually connected to DW APB GPIO
 	 * which acts as a wire between MB INTC and CPU INTC.

arch/arc/boot/dts/axs10x_mb.dtsi

@@ -9,6 +9,10 @@
  */
 
 / {
+	aliases {
+		ethernet = &gmac;
+	};
+
 	axs10x_mb {
 		compatible = "simple-bus";
 		#address-cells = <1>;
@@ -68,7 +72,7 @@ pguclk: pguclk {
 			};
 		};
 
-		ethernet@0x18000 {
+		gmac: ethernet@0x18000 {
 			#interrupt-cells = <1>;
 			compatible = "snps,dwmac";
 			reg = < 0x18000 0x2000 >;
@@ -81,6 +85,7 @@ ethernet@0x18000 {
 			max-speed = <100>;
 			resets = <&creg_rst 5>;
 			reset-names = "stmmaceth";
+			mac-address = [00 00 00 00 00 00]; /* Filled in by U-Boot */
 		};
 
 		ehci@0x40000 {

arch/arc/boot/dts/hsdk.dts

@@ -25,6 +25,10 @@ chosen {
 		bootargs = "earlycon=uart8250,mmio32,0xf0005000,115200n8 console=ttyS0,115200n8 debug print-fatal-signals=1";
 	};
 
+	aliases {
+		ethernet = &gmac;
+	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -163,7 +167,7 @@ mmcclk_biu: mmcclk-biu {
 			#clock-cells = <0>;
 		};
 
-		ethernet@8000 {
+		gmac: ethernet@8000 {
 			#interrupt-cells = <1>;
 			compatible = "snps,dwmac";
 			reg = <0x8000 0x2000>;
@@ -176,6 +180,8 @@ ethernet@8000 {
 			phy-handle = <&phy0>;
 			resets = <&cgu_rst HSDK_ETH_RESET>;
 			reset-names = "stmmaceth";
+			mac-address = [00 00 00 00 00 00]; /* Filled in by U-Boot */
+			dma-coherent;
 
 			mdio {
 				#address-cells = <1>;
@@ -194,12 +200,14 @@ ohci@60000 {
 			compatible = "snps,hsdk-v1.0-ohci", "generic-ohci";
 			reg = <0x60000 0x100>;
 			interrupts = <15>;
+			dma-coherent;
 		};
 
 		ehci@40000 {
 			compatible = "snps,hsdk-v1.0-ehci", "generic-ehci";
 			reg = <0x40000 0x100>;
 			interrupts = <15>;
+			dma-coherent;
 		};
 
 		mmc@a000 {
@@ -212,6 +220,7 @@ mmc@a000 {
 			clock-names = "biu", "ciu";
 			interrupts = <12>;
 			bus-width = <4>;
+			dma-coherent;
 		};
 	};
 

arch/arc/configs/axs101_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
-# CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -63,7 +61,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 CONFIG_MOUSE_SERIAL=y
 CONFIG_MOUSE_SYNAPTICS_USB=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y

arch/arc/configs/axs103_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
-# CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -64,7 +62,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 CONFIG_MOUSE_SERIAL=y
 CONFIG_MOUSE_SYNAPTICS_USB=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y

arch/arc/configs/axs103_smp_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
-# CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -65,7 +63,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 CONFIG_MOUSE_SERIAL=y
 CONFIG_MOUSE_SYNAPTICS_USB=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y

arch/arc/configs/haps_hs_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
@@ -57,7 +56,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/haps_hs_smp_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
@@ -60,7 +59,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/hsdk_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 CONFIG_SYSVIPC=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
 CONFIG_NO_HZ_IDLE=y

arch/arc/configs/nps_defconfig

@@ -59,7 +59,6 @@ CONFIG_NETCONSOLE=y
 # CONFIG_INPUT_MOUSE is not set
 # CONFIG_SERIO is not set
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/nsim_700_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
@@ -44,7 +43,6 @@ CONFIG_LXT_PHY=y
 # CONFIG_INPUT_MOUSE is not set
 # CONFIG_SERIO is not set
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_ARC=y
 CONFIG_SERIAL_ARC_CONSOLE=y
 # CONFIG_HW_RANDOM is not set

arch/arc/configs/nsim_hs_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 CONFIG_POSIX_MQUEUE=y
@@ -45,7 +44,6 @@ CONFIG_DEVTMPFS=y
 # CONFIG_INPUT_MOUSE is not set
 # CONFIG_SERIO is not set
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_ARC=y
 CONFIG_SERIAL_ARC_CONSOLE=y
 # CONFIG_HW_RANDOM is not set

arch/arc/configs/nsim_hs_smp_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 # CONFIG_CROSS_MEMORY_ATTACH is not set
 CONFIG_HIGH_RES_TIMERS=y
@@ -44,7 +43,6 @@ CONFIG_DEVTMPFS=y
 # CONFIG_INPUT_MOUSE is not set
 # CONFIG_SERIO is not set
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_ARC=y
 CONFIG_SERIAL_ARC_CONSOLE=y
 # CONFIG_HW_RANDOM is not set

arch/arc/configs/nsimosci_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -48,7 +47,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/nsimosci_hs_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -47,7 +46,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/nsimosci_hs_smp_defconfig

-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_SWAP is not set
 CONFIG_SYSVIPC=y
 # CONFIG_CROSS_MEMORY_ATTACH is not set
@@ -58,7 +57,6 @@ CONFIG_MOUSE_PS2_TOUCHKIT=y
 # CONFIG_SERIO_SERPORT is not set
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/tb10x_defconfig

@@ -57,7 +57,6 @@ CONFIG_STMMAC_ETH=y
 # CONFIG_SERIO is not set
 # CONFIG_VT is not set
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_NR_UARTS=1

arch/arc/configs/vdk_hs38_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_CROSS_MEMORY_ATTACH is not set
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_IKCONFIG=y
@@ -53,7 +52,6 @@ CONFIG_NATIONAL_PHY=y
 CONFIG_MOUSE_PS2_TOUCHKIT=y
 CONFIG_SERIO_ARC_PS2=y
 # CONFIG_LEGACY_PTYS is not set
-# CONFIG_DEVKMEM is not set
 CONFIG_SERIAL_8250=y
 CONFIG_SERIAL_8250_CONSOLE=y
 CONFIG_SERIAL_8250_DW=y

arch/arc/configs/vdk_hs38_smp_defconfig

 # CONFIG_LOCALVERSION_AUTO is not set
-CONFIG_DEFAULT_HOSTNAME="ARCLinux"
 # CONFIG_CROSS_MEMORY_ATTACH is not set
 CONFIG_HIGH_RES_TIMERS=y
 CONFIG_IKCONFIG=y

arch/arc/include/asm/atomic.h

@@ -84,7 +84,7 @@ static inline int atomic_fetch_##op(int i, atomic_t *v)			\
 	"1:	llock   %[orig], [%[ctr]]		\n"		\
 	"	" #asm_op " %[val], %[orig], %[i]	\n"		\
 	"	scond   %[val], [%[ctr]]		\n"		\
-	"						\n"		\
+	"	bnz     1b				\n"		\
 	: [val]	"=&r"	(val),						\
 	  [orig] "=&r" (orig)						\
 	: [ctr]	"r"	(&v->counter),					\

arch/arc/include/asm/dma-mapping.h

+// SPDX-License-Identifier:  GPL-2.0
+// (C) 2018 Synopsys, Inc. (www.synopsys.com)
+
+#ifndef ASM_ARC_DMA_MAPPING_H
+#define ASM_ARC_DMA_MAPPING_H
+
+#include <asm-generic/dma-mapping.h>
+
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			const struct iommu_ops *iommu, bool coherent);
+#define arch_setup_dma_ops arch_setup_dma_ops
+
+#endif

arch/arc/kernel/troubleshoot.c

@@ -83,9 +83,6 @@ static void print_task_path_n_nm(struct task_struct *tsk, char *buf)
 static void show_faulting_vma(unsigned long address, char *buf)
 {
 	struct vm_area_struct *vma;
-	struct inode *inode;
-	unsigned long ino = 0;
-	dev_t dev = 0;
 	char *nm = buf;
 	struct mm_struct *active_mm = current->active_mm;
 
@@ -99,12 +96,10 @@ static void show_faulting_vma(unsigned long address, char *buf)
 	 * if the container VMA is not found
 	 */
 	if (vma && (vma->vm_start <= address)) {
-		struct file *file = vma->vm_file;
-		if (file) {
-			nm = file_path(file, buf, PAGE_SIZE - 1);
-			inode = file_inode(vma->vm_file);
-			dev = inode->i_sb->s_dev;
-			ino = inode->i_ino;
+		if (vma->vm_file) {
+			nm = file_path(vma->vm_file, buf, PAGE_SIZE - 1);
+			if (IS_ERR(nm))
+				nm = "?";
 		}
 		pr_info("    @off 0x%lx in [%s]\n"
 			"    VMA: 0x%08lx to 0x%08lx\n",

arch/arc/mm/cache.c

@@ -65,7 +65,7 @@ char *arc_cache_mumbojumbo(int c, char *buf, int len)
 
 	n += scnprintf(buf + n, len - n, "Peripherals\t: %#lx%s%s\n",
 		       perip_base,
-		       IS_AVAIL3(ioc_exists, ioc_enable, ", IO-Coherency "));
+		       IS_AVAIL3(ioc_exists, ioc_enable, ", IO-Coherency (per-device) "));
 
 	return buf;
 }
@@ -896,15 +896,6 @@ static void __dma_cache_wback_slc(phys_addr_t start, unsigned long sz)
 	slc_op(start, sz, OP_FLUSH);
 }
 
-/*
- * DMA ops for systems with IOC
- * IOC hardware snoops all DMA traffic keeping the caches consistent with
- * memory - eliding need for any explicit cache maintenance of DMA buffers
- */
-static void __dma_cache_wback_inv_ioc(phys_addr_t start, unsigned long sz) {}
-static void __dma_cache_inv_ioc(phys_addr_t start, unsigned long sz) {}
-static void __dma_cache_wback_ioc(phys_addr_t start, unsigned long sz) {}
-
 /*
  * Exported DMA API
  */
@@ -1153,6 +1144,19 @@ noinline void __init arc_ioc_setup(void)
 {
 	unsigned int ioc_base, mem_sz;
 
+	/*
+	 * As for today we don't support both IOC and ZONE_HIGHMEM enabled
+	 * simultaneously. This happens because as of today IOC aperture covers
+	 * only ZONE_NORMAL (low mem) and any dma transactions outside this
+	 * region won't be HW coherent.
+	 * If we want to use both IOC and ZONE_HIGHMEM we can use
+	 * bounce_buffer to handle dma transactions to HIGHMEM.
+	 * Also it is possible to modify dma_direct cache ops or increase IOC
+	 * aperture size if we are planning to use HIGHMEM without PAE.
+	 */
+	if (IS_ENABLED(CONFIG_HIGHMEM))
+		panic("IOC and HIGHMEM can't be used simultaneously");
+
 	/* Flush + invalidate + disable L1 dcache */
 	__dc_disable();
 
@@ -1264,11 +1268,7 @@ void __init arc_cache_init_master(void)
 	if (is_isa_arcv2() && ioc_enable)
 		arc_ioc_setup();
 
-	if (is_isa_arcv2() && ioc_enable) {
-		__dma_cache_wback_inv = __dma_cache_wback_inv_ioc;
-		__dma_cache_inv = __dma_cache_inv_ioc;
-		__dma_cache_wback = __dma_cache_wback_ioc;
-	} else if (is_isa_arcv2() && l2_line_sz && slc_enable) {
+	if (is_isa_arcv2() && l2_line_sz && slc_enable) {
 		__dma_cache_wback_inv = __dma_cache_wback_inv_slc;
 		__dma_cache_inv = __dma_cache_inv_slc;
 		__dma_cache_wback = __dma_cache_wback_slc;
@@ -1277,6 +1277,12 @@ void __init arc_cache_init_master(void)
 		__dma_cache_inv = __dma_cache_inv_l1;
 		__dma_cache_wback = __dma_cache_wback_l1;
 	}
+	/*
+	 * In case of IOC (say IOC+SLC case), pointers above could still be set
+	 * but end up not being relevant as the first function in chain is not
+	 * called at all for @dma_direct_ops
+	 *     arch_sync_dma_for_cpu() -> dma_cache_*() -> __dma_cache_*()
+	 */
 }
 
 void __ref arc_cache_init(void)

arch/arc/mm/dma.c

@@ -6,20 +6,17 @@
  * published by the Free Software Foundation.
  */
 
-/*
- * DMA Coherent API Notes
- *
- * I/O is inherently non-coherent on ARC. So a coherent DMA buffer is
- * implemented by accessing it using a kernel virtual address, with
- * Cache bit off in the TLB entry.
- *
- * The default DMA address == Phy address which is 0x8000_0000 based.
- */
-
 #include <linux/dma-noncoherent.h>
 #include <asm/cache.h>
 #include <asm/cacheflush.h>
 
+/*
+ * ARCH specific callbacks for generic noncoherent DMA ops (dma/noncoherent.c)
+ *  - hardware IOC not available (or "dma-coherent" not set for device in DT)
+ *  - But still handle both coherent and non-coherent requests from caller
+ *
+ * For DMA coherent hardware (IOC) generic code suffices
+ */
 void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 		gfp_t gfp, unsigned long attrs)
 {
@@ -27,42 +24,29 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
 	struct page *page;
 	phys_addr_t paddr;
 	void *kvaddr;
-	int need_coh = 1, need_kvaddr = 0;
-
-	page = alloc_pages(gfp, order);
-	if (!page)
-		return NULL;
+	bool need_coh = !(attrs & DMA_ATTR_NON_CONSISTENT);
 
 	/*
-	 * IOC relies on all data (even coherent DMA data) being in cache
-	 * Thus allocate normal cached memory
-	 *
-	 * The gains with IOC are two pronged:
-	 *   -For streaming data, elides need for cache maintenance, saving
-	 *    cycles in flush code, and bus bandwidth as all the lines of a
-	 *    buffer need to be flushed out to memory
-	 *   -For coherent data, Read/Write to buffers terminate early in cache
-	 *   (vs. always going to memory - thus are faster)
+	 * __GFP_HIGHMEM flag is cleared by upper layer functions
+	 * (in include/linux/dma-mapping.h) so we should never get a
+	 * __GFP_HIGHMEM here.
 	 */
-	if ((is_isa_arcv2() && ioc_enable) ||
-	    (attrs & DMA_ATTR_NON_CONSISTENT))
-		need_coh = 0;
+	BUG_ON(gfp & __GFP_HIGHMEM);
 
-	/*
-	 * - A coherent buffer needs MMU mapping to enforce non-cachability
-	 * - A highmem page needs a virtual handle (hence MMU mapping)
-	 *   independent of cachability
-	 */
-	if (PageHighMem(page) || need_coh)
-		need_kvaddr = 1;
+	page = alloc_pages(gfp, order);
+	if (!page)
+		return NULL;
 
 	/* This is linear addr (0x8000_0000 based) */
 	paddr = page_to_phys(page);
 
 	*dma_handle = paddr;
 
-	/* This is kernel Virtual address (0x7000_0000 based) */
-	if (need_kvaddr) {
+	/*
+	 * A coherent buffer needs MMU mapping to enforce non-cachability.
+	 * kvaddr is kernel Virtual address (0x7000_0000 based).
+	 */
+	if (need_coh) {
 		kvaddr = ioremap_nocache(paddr, size);
 		if (kvaddr == NULL) {
 			__free_pages(page, order);
@@ -93,12 +77,8 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
 {
 	phys_addr_t paddr = dma_handle;
 	struct page *page = virt_to_page(paddr);
-	int is_non_coh = 1;
-
-	is_non_coh = (attrs & DMA_ATTR_NON_CONSISTENT) ||
-			(is_isa_arcv2() && ioc_enable);
 
-	if (PageHighMem(page) || !is_non_coh)
+	if (!(attrs & DMA_ATTR_NON_CONSISTENT))
 		iounmap((void __force __iomem *)vaddr);
 
 	__free_pages(page, get_order(size));
@@ -185,3 +165,23 @@ void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
 		break;
 	}
 }
+
+/*
+ * Plug in coherent or noncoherent dma ops
+ */
+void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
+			const struct iommu_ops *iommu, bool coherent)
+{
+	/*
+	 * IOC hardware snoops all DMA traffic keeping the caches consistent
+	 * with memory - eliding need for any explicit cache maintenance of
+	 * DMA buffers - so we can use dma_direct cache ops.
+	 */
+	if (is_isa_arcv2() && ioc_enable && coherent) {
+		set_dma_ops(dev, &dma_direct_ops);
+		dev_info(dev, "use dma_direct_ops cache ops\n");
+	} else {
+		set_dma_ops(dev, &dma_noncoherent_ops);
+		dev_info(dev, "use dma_noncoherent_ops cache ops\n");
+	}
+}