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[05/10] riscv: Add SOC early init support

Message ID 20200212103432.660256-6-damien.lemoal@wdc.com (mailing list archive)
State New, archived
Headers show
Series Kendryte k210 SoC boards support | expand

Commit Message

Damien Le Moal Feb. 12, 2020, 10:34 a.m. UTC 
Add a mechanism for early SoC initialization for platforms that need
additional hardware initialization not possible through the regular
device tree and drivers mechanism. With this, a SoC specific
initialization function can be called very early, before DTB parsing
is done by parse_dtb() in Linux RISC-V kernel setup code.

This can be very useful for early hardware initialization for No-MMU
kernels booted directly in M-mode because it is quite likely that no
other booting stage exist prior to the No-MMU kernel.

Example use of a SoC early initialization is as follows:

static void vendor_abc_early_init(const void *fdt)
{
	/*
	 * some early init code here that can use simple matches
	 * against the flat device tree file.
	 */
}
SOC_EARLY_INIT_DECLARE("vendor,abc", abc_early_init);

This early initialization function is executed only if the flat device
tree for the board has a 'compatible = "vendor,abc"' entry;

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Anup Patel <anup.patel@wdc.com>
---
 arch/riscv/include/asm/soc.h    | 23 +++++++++++++++++++++++
 arch/riscv/kernel/Makefile      |  1 +
 arch/riscv/kernel/head.S        |  1 +
 arch/riscv/kernel/soc.c         | 28 ++++++++++++++++++++++++++++
 arch/riscv/kernel/vmlinux.lds.S |  6 ++++++
 5 files changed, 59 insertions(+)
 create mode 100644 arch/riscv/include/asm/soc.h
 create mode 100644 arch/riscv/kernel/soc.c

Comments

Palmer Dabbelt March 4, 2020, 7:28 p.m. UTC | #1 
On Wed, 12 Feb 2020 02:34:27 PST (-0800), Damien Le Moal wrote:
> Add a mechanism for early SoC initialization for platforms that need
> additional hardware initialization not possible through the regular
> device tree and drivers mechanism. With this, a SoC specific
> initialization function can be called very early, before DTB parsing
> is done by parse_dtb() in Linux RISC-V kernel setup code.
>
> This can be very useful for early hardware initialization for No-MMU
> kernels booted directly in M-mode because it is quite likely that no
> other booting stage exist prior to the No-MMU kernel.
>
> Example use of a SoC early initialization is as follows:
>
> static void vendor_abc_early_init(const void *fdt)
> {
> 	/*
> 	 * some early init code here that can use simple matches
> 	 * against the flat device tree file.
> 	 */
> }
> SOC_EARLY_INIT_DECLARE("vendor,abc", abc_early_init);
>
> This early initialization function is executed only if the flat device
> tree for the board has a 'compatible = "vendor,abc"' entry;
>
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> Signed-off-by: Anup Patel <anup.patel@wdc.com>
> ---
>  arch/riscv/include/asm/soc.h    | 23 +++++++++++++++++++++++
>  arch/riscv/kernel/Makefile      |  1 +
>  arch/riscv/kernel/head.S        |  1 +
>  arch/riscv/kernel/soc.c         | 28 ++++++++++++++++++++++++++++
>  arch/riscv/kernel/vmlinux.lds.S |  6 ++++++
>  5 files changed, 59 insertions(+)
>  create mode 100644 arch/riscv/include/asm/soc.h
>  create mode 100644 arch/riscv/kernel/soc.c
>
> diff --git a/arch/riscv/include/asm/soc.h b/arch/riscv/include/asm/soc.h
> new file mode 100644
> index 000000000000..9b8c332cbe76
> --- /dev/null
> +++ b/arch/riscv/include/asm/soc.h
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + */
> +
> +#ifndef _ASM_RISCV_SOC_H
> +#define _ASM_RISCV_SOC_H
> +
> +#include <linux/of.h>
> +#include <linux/linkage.h>
> +#include <linux/types.h>
> +
> +#define SOC_EARLY_INIT_DECLARE(compat, fn)				\
> +	static const struct of_device_id __soc_early_init		\
> +		__used __section(__soc_early_init_table)		\
> +		 = { .compatible = compat, .data = fn  }
> +
> +void soc_early_init(void);
> +
> +extern unsigned long __soc_early_init_table_start;
> +extern unsigned long __soc_early_init_table_end;
> +
> +#endif
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 97d0c35f8b37..e4a22999dbc6 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -10,6 +10,7 @@ endif
>  extra-y += head.o
>  extra-y += vmlinux.lds
>
> +obj-y	+= soc.o
>  obj-y	+= cpu.o
>  obj-y	+= cpufeature.o
>  obj-y	+= entry.o
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 271860fc2c3f..a7768d6165d4 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -125,6 +125,7 @@ clear_bss_done:
>  	call kasan_early_init
>  #endif
>  	/* Start the kernel */
> +	call soc_early_init
>  	call parse_dtb
>  	tail start_kernel
>
> diff --git a/arch/riscv/kernel/soc.c b/arch/riscv/kernel/soc.c
> new file mode 100644
> index 000000000000..0b3b3dc9ad0f
> --- /dev/null
> +++ b/arch/riscv/kernel/soc.c
> @@ -0,0 +1,28 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2020 Western Digital Corporation or its affiliates.
> + */
> +#include <linux/init.h>
> +#include <linux/libfdt.h>
> +#include <asm/pgtable.h>
> +#include <asm/soc.h>
> +
> +/*
> + * This is called extremly early, before parse_dtb(), to allow initializing
> + * SoC hardware before memory or any device driver initialization.
> + */
> +void __init soc_early_init(void)
> +{
> +	void (*early_fn)(const void *fdt);
> +	const struct of_device_id *s;
> +	const void *fdt = dtb_early_va;
> +
> +	for (s = (void *)&__soc_early_init_table_start;
> +	     (void *)s < (void *)&__soc_early_init_table_end; s++) {
> +		if (!fdt_node_check_compatible(fdt, 0, s->compatible)) {
> +			early_fn = s->data;
> +			early_fn(fdt);
> +			return;
> +		}
> +	}
> +}
> diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
> index 1e0193ded420..32b160942f40 100644
> --- a/arch/riscv/kernel/vmlinux.lds.S
> +++ b/arch/riscv/kernel/vmlinux.lds.S
> @@ -24,6 +24,12 @@ SECTIONS
>  	HEAD_TEXT_SECTION
>  	INIT_TEXT_SECTION(PAGE_SIZE)
>  	INIT_DATA_SECTION(16)
> +	. = ALIGN(8);
> +	__soc_early_init_table : {
> +		__soc_early_init_table_start = .;
> +		KEEP(*(__soc_early_init_table))
> +		__soc_early_init_table_end = .;
> +	}
>  	/* we have to discard exit text and such at runtime, not link time */
>  	.exit.text :
>  	{

I suppose my only worry here is that __init isn't going to be sufficient for
these sorts of fixups on all systems so we'll need something more special, but
that's just speculation so let's cross that bridge when we come to it.

Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>

Thanks!
diff mbox series

Patch

diff --git a/arch/riscv/include/asm/soc.h b/arch/riscv/include/asm/soc.h
new file mode 100644
index 000000000000..9b8c332cbe76
--- /dev/null
+++ b/arch/riscv/include/asm/soc.h
@@ -0,0 +1,23 @@ 
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+
+#ifndef _ASM_RISCV_SOC_H
+#define _ASM_RISCV_SOC_H
+
+#include <linux/of.h>
+#include <linux/linkage.h>
+#include <linux/types.h>
+
+#define SOC_EARLY_INIT_DECLARE(compat, fn)				\
+	static const struct of_device_id __soc_early_init		\
+		__used __section(__soc_early_init_table)		\
+		 = { .compatible = compat, .data = fn  }
+
+void soc_early_init(void);
+
+extern unsigned long __soc_early_init_table_start;
+extern unsigned long __soc_early_init_table_end;
+
+#endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 97d0c35f8b37..e4a22999dbc6 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -10,6 +10,7 @@  endif
 extra-y += head.o
 extra-y += vmlinux.lds
 
+obj-y	+= soc.o
 obj-y	+= cpu.o
 obj-y	+= cpufeature.o
 obj-y	+= entry.o
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 271860fc2c3f..a7768d6165d4 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -125,6 +125,7 @@  clear_bss_done:
 	call kasan_early_init
 #endif
 	/* Start the kernel */
+	call soc_early_init
 	call parse_dtb
 	tail start_kernel
 
diff --git a/arch/riscv/kernel/soc.c b/arch/riscv/kernel/soc.c
new file mode 100644
index 000000000000..0b3b3dc9ad0f
--- /dev/null
+++ b/arch/riscv/kernel/soc.c
@@ -0,0 +1,28 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2020 Western Digital Corporation or its affiliates.
+ */
+#include <linux/init.h>
+#include <linux/libfdt.h>
+#include <asm/pgtable.h>
+#include <asm/soc.h>
+
+/*
+ * This is called extremly early, before parse_dtb(), to allow initializing
+ * SoC hardware before memory or any device driver initialization.
+ */
+void __init soc_early_init(void)
+{
+	void (*early_fn)(const void *fdt);
+	const struct of_device_id *s;
+	const void *fdt = dtb_early_va;
+
+	for (s = (void *)&__soc_early_init_table_start;
+	     (void *)s < (void *)&__soc_early_init_table_end; s++) {
+		if (!fdt_node_check_compatible(fdt, 0, s->compatible)) {
+			early_fn = s->data;
+			early_fn(fdt);
+			return;
+		}
+	}
+}
diff --git a/arch/riscv/kernel/vmlinux.lds.S b/arch/riscv/kernel/vmlinux.lds.S
index 1e0193ded420..32b160942f40 100644
--- a/arch/riscv/kernel/vmlinux.lds.S
+++ b/arch/riscv/kernel/vmlinux.lds.S
@@ -24,6 +24,12 @@  SECTIONS
 	HEAD_TEXT_SECTION
 	INIT_TEXT_SECTION(PAGE_SIZE)
 	INIT_DATA_SECTION(16)
+	. = ALIGN(8);
+	__soc_early_init_table : {
+		__soc_early_init_table_start = .;
+		KEEP(*(__soc_early_init_table))
+		__soc_early_init_table_end = .;
+	}
 	/* we have to discard exit text and such at runtime, not link time */
 	.exit.text :
 	{