microblaze: Remove noMMU code

This configuration is obsolete and likely none is really using it. That's
why remove it to simplify code.

Note about CONFIG_MMU in hw_exception_handler.S is left intentionally
for better comment understanding.

Cc: Mike Rapoport <rppt@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/43486cab370e0c0a79860120b71e0caac75a7e44.1606397528.git.michal.simek@xilinx.com

Author: Michal Simek

arch/microblaze/Kconfig

@@ -3,19 +3,17 @@ config MICROBLAZE
 	def_bool y
 	select ARCH_32BIT_OFF_T
 	select ARCH_NO_SWAP
-	select ARCH_HAS_BINFMT_FLAT if !MMU
 	select ARCH_HAS_DMA_PREP_COHERENT
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_SYNC_DMA_FOR_CPU
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_HAS_DMA_SET_UNCACHED if !MMU
 	select ARCH_MIGHT_HAVE_PC_PARPORT
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_TABLE_SORT
 	select TIMER_OF
 	select CLONE_BACKWARDS3
 	select COMMON_CLK
-	select DMA_DIRECT_REMAP if MMU
+	select DMA_DIRECT_REMAP
 	select GENERIC_ATOMIC64
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_CPU_DEVICES
@@ -45,7 +43,7 @@ config MICROBLAZE
 	select TRACING_SUPPORT
 	select VIRT_TO_BUS
 	select CPU_NO_EFFICIENT_FFS
-	select MMU_GATHER_NO_RANGE if MMU
+	select MMU_GATHER_NO_RANGE
 	select SPARSE_IRQ
 	select SET_FS
 
@@ -96,8 +94,7 @@ menu "Processor type and features"
 source "kernel/Kconfig.hz"
 
 config MMU
-	bool "MMU support"
-	default n
+	def_bool y
 
 comment "Boot options"
 
@@ -143,18 +140,8 @@ config ADVANCED_OPTIONS
 comment "Default settings for advanced configuration options are used"
 	depends on !ADVANCED_OPTIONS
 
-config XILINX_UNCACHED_SHADOW
-	bool "Are you using uncached shadow for RAM ?"
-	depends on ADVANCED_OPTIONS && !MMU
-	default n
-	help
-	  This is needed to be able to allocate uncachable memory regions.
-	  The feature requires the design to define the RAM memory controller
-	  window to be twice as large as the actual physical memory.
-
 config HIGHMEM
 	bool "High memory support"
-	depends on MMU
 	help
 	  The address space of Microblaze processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address
@@ -167,7 +154,7 @@ config HIGHMEM
 
 config LOWMEM_SIZE_BOOL
 	bool "Set maximum low memory"
-	depends on ADVANCED_OPTIONS && MMU
+	depends on ADVANCED_OPTIONS
 	help
 	  This option allows you to set the maximum amount of memory which
 	  will be used as "low memory", that is, memory which the kernel can
@@ -205,12 +192,11 @@ config KERNEL_START_BOOL
 
 config KERNEL_START
 	hex "Virtual address of kernel base" if KERNEL_START_BOOL
-	default "0xc0000000" if MMU
-	default KERNEL_BASE_ADDR if !MMU
+	default "0xc0000000"
 
 config TASK_SIZE_BOOL
 	bool "Set custom user task size"
-	depends on ADVANCED_OPTIONS && MMU
+	depends on ADVANCED_OPTIONS
 	help
 	  This option allows you to set the amount of virtual address space
 	  allocated to user tasks.  This can be useful in optimizing the
@@ -222,33 +208,6 @@ config TASK_SIZE
 	hex "Size of user task space" if TASK_SIZE_BOOL
 	default "0x80000000"
 
-choice
-	prompt "Page size"
-	default MICROBLAZE_4K_PAGES
-	depends on ADVANCED_OPTIONS && !MMU
-	help
-	  Select the kernel logical page size. Increasing the page size
-	  will reduce software overhead at each page boundary, allow
-	  hardware prefetch mechanisms to be more effective, and allow
-	  larger dma transfers increasing IO efficiency and reducing
-	  overhead. However the utilization of memory will increase.
-	  For example, each cached file will using a multiple of the
-	  page size to hold its contents and the difference between the
-	  end of file and the end of page is wasted.
-
-	  If unsure, choose 4K_PAGES.
-
-config MICROBLAZE_4K_PAGES
-	bool "4k page size"
-
-config MICROBLAZE_16K_PAGES
-	bool "16k page size"
-
-config MICROBLAZE_64K_PAGES
-	bool "64k page size"
-
-endchoice
-
 endmenu
 
 menu "Bus Options"

arch/microblaze/Makefile

@@ -1,11 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 KBUILD_DEFCONFIG := mmu_defconfig
 
-ifeq ($(CONFIG_MMU),y)
 UTS_SYSNAME = -DUTS_SYSNAME=\"Linux\"
-else
-UTS_SYSNAME = -DUTS_SYSNAME=\"uClinux\"
-endif
 
 # What CPU vesion are we building for, and crack it open
 # as major.minor.rev
@@ -67,12 +63,7 @@ DTB:=$(subst simpleImage.,,$(filter simpleImage.%, $(MAKECMDGOALS)))
 
 core-y	+= $(boot)/dts/
 
-# defines filename extension depending memory management type
-ifeq ($(CONFIG_MMU),)
-MMU := -nommu
-endif
-
-export MMU DTB
+export DTB
 
 all: linux.bin
 

arch/microblaze/configs/mmu_defconfig

@@ -16,7 +16,6 @@ CONFIG_XILINX_MICROBLAZE0_USE_DIV=1
 CONFIG_XILINX_MICROBLAZE0_USE_HW_MUL=2
 CONFIG_XILINX_MICROBLAZE0_USE_FPU=2
 CONFIG_HZ_100=y
-CONFIG_MMU=y
 CONFIG_CMDLINE_BOOL=y
 CONFIG_CMDLINE_FORCE=y
 CONFIG_HIGHMEM=y

arch/microblaze/configs/nommu_defconfig

@@ -6,14 +6,8 @@
 #ifndef _ASM_MICROBLAZE_DMA_H
 #define _ASM_MICROBLAZE_DMA_H
 
-#ifndef CONFIG_MMU
-/* we don't have dma address limit. define it as zero to be
- * unlimited. */
-#define MAX_DMA_ADDRESS		(0)
-#else
 /* Virtual address corresponding to last available physical memory address.  */
 #define MAX_DMA_ADDRESS (CONFIG_KERNEL_START + memory_size - 1)
-#endif
 
 #ifdef CONFIG_PCI
 extern int isa_dma_bridge_buggy;

arch/microblaze/include/asm/dma.h

@@ -11,11 +11,6 @@
 #define _ASM_MICROBLAZE_EXCEPTIONS_H
 
 #ifdef __KERNEL__
-
-#ifndef CONFIG_MMU
-#define EX_HANDLER_STACK_SIZ	(4*19)
-#endif
-
 #ifndef __ASSEMBLY__
 
 /* Macros to enable and disable HW exceptions in the MSR */

arch/microblaze/include/asm/exceptions.h

@@ -30,15 +30,12 @@ extern resource_size_t isa_mem_base;
 #define PCI_IOBASE	((void __iomem *)_IO_BASE)
 #define IO_SPACE_LIMIT (0xFFFFFFFF)
 
-#ifdef CONFIG_MMU
 #define page_to_bus(page)	(page_to_phys(page))
 
 extern void iounmap(volatile void __iomem *addr);
 
 extern void __iomem *ioremap(phys_addr_t address, unsigned long size);
 
-#endif /* CONFIG_MMU */
-
 /* Big Endian */
 #define out_be32(a, v) __raw_writel((v), (void __iomem __force *)(a))
 #define out_be16(a, v) __raw_writew((v), (a))

arch/microblaze/include/asm/io.h

@@ -8,9 +8,6 @@
 #ifndef _ASM_MICROBLAZE_MMU_H
 #define _ASM_MICROBLAZE_MMU_H
 
-# ifndef CONFIG_MMU
-#  include <asm-generic/mmu.h>
-# else /* CONFIG_MMU */
 #  ifdef __KERNEL__
 #   ifndef __ASSEMBLY__
 
@@ -119,5 +116,4 @@ extern u32 tlb_skip;
 #  define TLB_G			0x00000001 /* Memory is guarded from prefetch */
 
 #  endif /* __KERNEL__ */
-# endif /* CONFIG_MMU */
 #endif /* _ASM_MICROBLAZE_MMU_H */

arch/microblaze/include/asm/mmu.h

@@ -1,6 +1,2 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifdef CONFIG_MMU
 # include <asm/mmu_context_mm.h>
-#else
-# include <asm-generic/mmu_context.h>
-#endif