On Tue, Jan 21, 2020 at 08:27:41PM +0100, 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 passed DTB
> instead, if available. Note that for now this is limited to DTBs passed
> explicitly by the boot loader. DTBs appended to a zImage or uImage are
> not inspected. 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>
> ---
> Against arm/for-next.
>
> Tested with the following configurations:
> - zImage + DTB (r8a7791/koelsch): physical memory start address
> obtained from DT,
> - uImage + DTB (r8a73a4/ape6evm, r7s72100/rskrza1, r7s9210/rza2mevb):
> physical memory start address obtained from DT,
> - zImage with appended DTB (r8a7740/armadillo, sh73a0/kzm9g): physical
> memory start address obtained by masking, as before.
>
> An appended DTB is currently processed after the start of physical
> memory is obtained. Hence obtaining that address from an appended DTB
> requires moving/copying that copy. Given the complexity w.r.t. the
> "restart" label, and the lack of a need for me to support this, I didn't
> implement that part.
> ---
> arch/arm/boot/compressed/Makefile | 6 ++-
> arch/arm/boot/compressed/fdt_get_mem_start.c | 52 ++++++++++++++++++++
> arch/arm/boot/compressed/head.S | 16 +++++-
> 3 files changed, 72 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..cb4e6a84b156c204 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -235,8 +235,20 @@ 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 passed DTB first, if available.
> + */
> + mov r0, r8
> + bl fdt_get_mem_start
NAK. You don't have a stack setup here. The fact this works for you
is merely due to "sp" happening to be pointing somewhere sane, but
there is no such requirement. Therefore, this is fragile.
> + mov r4, r0
> + cmn r0, #1
> + bne 1f
> +#endif
> +
> + /*
> + * 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 +266,8 @@ not_angel:
> */
> mov r4, pc
> and r4, r4, #0xf8000000
> +
> +1:
> /* Determine final kernel image address. */
> add r4, r4, #TEXT_OFFSET
> #else
> --
> 2.17.1
>
>
--
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