On Mon, 27 Jan 2020, Geert Uytterhoeven wrote: > Currently, the start address of physical memory is obtained by masking > the program counter with a fixed mask of 0xf8000000. This mask value > was chosen as a balance between the requirements of different platforms. > However, this does require that the start address of physical memory is > a multiple of 128 MiB, precluding booting Linux on platforms where this > requirement is not fulfilled. > > Fix this limitation by obtaining the start address from the DTB instead, > if available (either explicitly passed, or appended to the kernel). > Fall back to the traditional method when needed. > > This allows to boot Linux on r7s9210/rza2mevb using the 64 MiB of SDRAM > on the RZA2MEVB sub board, which is located at 0x0C000000 (CS3 space), > i.e. not at a multiple of 128 MiB. > > Suggested-by: Nicolas Pitre <nico@xxxxxxxxxxx> > Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> Reviewed-by: Nicolas Pitre <nico@xxxxxxxxxxx> > --- > Against arm/for-next. > > Tested with the following configurations: > - zImage + DTB (r8a7791/koelsch), > - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb), > - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g). > > v2: > - Use "cmp r0, #-1", instead of "cmn r0, #1", > - Add missing stack setup, > - Support appended DTBs. > > v1: https://lore.kernel.org/linux-arm-kernel/20200121192741.20597-1-geert+renesas@xxxxxxxxx/ > --- > arch/arm/boot/compressed/Makefile | 6 ++- > arch/arm/boot/compressed/fdt_get_mem_start.c | 52 ++++++++++++++++++++ > arch/arm/boot/compressed/head.S | 52 +++++++++++++++++++- > 3 files changed, 108 insertions(+), 2 deletions(-) > create mode 100644 arch/arm/boot/compressed/fdt_get_mem_start.c > > diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile > index da599c3a11934332..bbfecd648a1a3b57 100644 > --- a/arch/arm/boot/compressed/Makefile > +++ b/arch/arm/boot/compressed/Makefile > @@ -86,12 +86,15 @@ libfdt_objs := $(addsuffix .o, $(basename $(libfdt))) > $(addprefix $(obj)/,$(libfdt) $(libfdt_hdrs)): $(obj)/%: $(srctree)/scripts/dtc/libfdt/% > $(call cmd,shipped) > > -$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o): \ > +$(addprefix $(obj)/,$(libfdt_objs) atags_to_fdt.o fdt_get_mem_start.o): \ > $(addprefix $(obj)/,$(libfdt_hdrs)) > > ifeq ($(CONFIG_ARM_ATAG_DTB_COMPAT),y) > OBJS += $(libfdt_objs) atags_to_fdt.o > endif > +ifeq ($(CONFIG_USE_OF),y) > +OBJS += $(libfdt_objs) fdt_get_mem_start.o > +endif > > targets := vmlinux vmlinux.lds piggy_data piggy.o \ > lib1funcs.o ashldi3.o bswapsdi2.o \ > @@ -116,6 +119,7 @@ CFLAGS_fdt.o := $(nossp-flags-y) > CFLAGS_fdt_ro.o := $(nossp-flags-y) > CFLAGS_fdt_rw.o := $(nossp-flags-y) > CFLAGS_fdt_wip.o := $(nossp-flags-y) > +CFLAGS_fdt_get_mem_start.o := $(nossp-flags-y) > > ccflags-y := -fpic $(call cc-option,-mno-single-pic-base,) -fno-builtin -I$(obj) > asflags-y := -DZIMAGE > diff --git a/arch/arm/boot/compressed/fdt_get_mem_start.c b/arch/arm/boot/compressed/fdt_get_mem_start.c > new file mode 100644 > index 0000000000000000..2c5ac47f656317ee > --- /dev/null > +++ b/arch/arm/boot/compressed/fdt_get_mem_start.c > @@ -0,0 +1,52 @@ > +// SPDX-License-Identifier: GPL-2.0-only > + > +#include <libfdt.h> > + > +static const void *getprop(const void *fdt, const char *node_path, > + const char *property) > +{ > + int offset = fdt_path_offset(fdt, node_path); > + > + if (offset == -FDT_ERR_NOTFOUND) > + return NULL; > + > + return fdt_getprop(fdt, offset, property, NULL); > +} > + > +static uint32_t get_addr_size(const void *fdt) > +{ > + const __be32 *addr_len = getprop(fdt, "/", "#address-cells"); > + > + if (!addr_len) { > + /* default */ > + return 1; > + } > + > + return fdt32_to_cpu(*addr_len); > +} > + > +/* > + * Get the start of physical memory > + */ > + > +unsigned long fdt_get_mem_start(const void *fdt) > +{ > + const __be32 *memory; > + uint32_t addr_size; > + > + if (!fdt) > + return -1; > + > + if (*(__be32 *)fdt != cpu_to_fdt32(FDT_MAGIC)) > + return -1; > + > + /* Find the first memory node */ > + memory = getprop(fdt, "/memory", "reg"); > + if (!memory) > + return -1; > + > + /* There may be multiple cells on LPAE platforms */ > + addr_size = get_addr_size(fdt); > + > + return fdt32_to_cpu(memory[addr_size - 1]); > +} > diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S > index 927f5dc413d7dff2..aa2d7de2ddc86fa8 100644 > --- a/arch/arm/boot/compressed/head.S > +++ b/arch/arm/boot/compressed/head.S > @@ -235,8 +235,56 @@ not_angel: > .text > > #ifdef CONFIG_AUTO_ZRELADDR > +#ifdef CONFIG_USE_OF > /* > - * Find the start of physical memory. As we are executing > + * Find the start of physical memory. > + * Try the DTB first, if available. > + */ > + adr r0, LC0 > + ldr r1, [r0] @ get absolute LC0 > + ldr sp, [r0, #28] @ get stack location > + sub r1, r0, r1 @ compute relocation offset > + add sp, sp, r1 @ apply relocation > + > +#ifdef CONFIG_ARM_APPENDED_DTB > + /* > + * Look for an appended DTB. If found, use it and > + * move stack away from it. > + */ > + ldr r6, [r0, #12] @ get &_edata > + add r6, r6, r1 @ relocate it > + ldmia r6, {r0, r5} @ get DTB signature and size > +#ifndef __ARMEB__ > + ldr r1, =0xedfe0dd0 @ sig is 0xd00dfeed big endian > + /* convert DTB size to little endian */ > + eor r2, r5, r5, ror #16 > + bic r2, r2, #0x00ff0000 > + mov r5, r5, ror #8 > + eor r5, r5, r2, lsr #8 > +#else > + ldr r1, =0xd00dfeed > +#endif > + cmp r0, r1 @ do we have a DTB there? > + bne 1f > + > + mov r8, r6 @ use it if so > + /* preserve 64-bit alignment */ > + add r5, r5, #7 > + bic r5, r5, #7 > + add sp, sp, r5 @ and move stack above it > + > +1: > +#endif /* CONFIG_ARM_APPENDED_DTB */ > + > + mov r0, r8 > + bl fdt_get_mem_start > + mov r4, r0 > + cmp r0, #-1 > + bne 1f > +#endif /* CONFIG_USE_OF */ > + > + /* > + * Fall back to the traditional method. As we are executing > * without the MMU on, we are in the physical address space. > * We just need to get rid of any offset by aligning the > * address. > @@ -254,6 +302,8 @@ not_angel: > */ > mov r4, pc > and r4, r4, #0xf8000000 > + > +1: > /* Determine final kernel image address. */ > add r4, r4, #TEXT_OFFSET > #else > -- > 2.17.1 > >
