[PATCH v3 0/2] EFI earlyprintk support

[PATCH v3 0/2] EFI earlyprintk support

[Matt Fleming]

From: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

These two patches cleanup the #include <linux/efi.h> duplication and get
rid of the #ifdef CONFIG_X86 in efi.h, and add support for
earlyprintk=efi, which is the only way users can debug early boot
crashes without special hardware.

Matt Fleming (2):
  efi: Add asm-generic/efi.h for non-x86
  x86/efi: Add EFI framebuffer earlyprintk support

 Documentation/kernel-parameters.txt  |   8 +-
 arch/ia64/include/asm/efi.h          |   6 ++
 arch/x86/Kconfig.debug               |   9 ++
 arch/x86/boot/compressed/eboot.c     |   1 -
 arch/x86/include/asm/efi.h           |  12 +++
 arch/x86/kernel/early_printk.c       |   6 ++
 arch/x86/kernel/setup.c              |   1 -
 arch/x86/platform/efi/Makefile       |   1 +
 arch/x86/platform/efi/early_printk.c | 191 +++++++++++++++++++++++++++++++++++
 arch/x86/platform/efi/efi.c          |   1 -
 arch/x86/platform/efi/efi_32.c       |   1 -
 arch/x86/platform/efi/efi_64.c       |   1 -
 arch/x86/platform/uv/bios_uv.c       |   1 -
 include/asm-generic/efi.h            |  17 ++++
 include/linux/efi.h                  |  31 +-----
 15 files changed, 249 insertions(+), 38 deletions(-)
 create mode 100644 arch/ia64/include/asm/efi.h
 create mode 100644 arch/x86/platform/efi/early_printk.c
 create mode 100644 include/asm-generic/efi.h

-- 
1.8.1.4

[PATCH 1/2] efi: Add asm-generic/efi.h for non-x86

[Matt Fleming]

From: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>

>From the #ifdef CONFIG_X86 in linux/efi.h it's clear we need a place to
declare functions that are implemented differently for each
architecture.

Since it's only x86 that needs to do special things, add a generic EFI
header file that can be used by everyone else and move the x86-specific
stuff to arch/x86/include/asm/efi.h.

Because the asm files are now included from linux/efi.h directly, this
change means we no longer have to include the asm file explicitly from C
files, allowing us to delete quite a few #include lines.

Cc: H. Peter Anvin <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Cc: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Cc: Tony Luck <tony.luck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Cc: Leif Lindholm <leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Signed-off-by: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
 arch/ia64/include/asm/efi.h      |  6 ++++++
 arch/x86/boot/compressed/eboot.c |  1 -
 arch/x86/include/asm/efi.h       | 10 ++++++++++
 arch/x86/kernel/setup.c          |  1 -
 arch/x86/platform/efi/efi.c      |  1 -
 arch/x86/platform/efi/efi_32.c   |  1 -
 arch/x86/platform/efi/efi_64.c   |  1 -
 arch/x86/platform/uv/bios_uv.c   |  1 -
 include/asm-generic/efi.h        | 17 +++++++++++++++++
 include/linux/efi.h              | 31 ++-----------------------------
 10 files changed, 35 insertions(+), 35 deletions(-)
 create mode 100644 arch/ia64/include/asm/efi.h
 create mode 100644 include/asm-generic/efi.h

diff --git a/arch/ia64/include/asm/efi.h b/arch/ia64/include/asm/efi.h
new file mode 100644
index 0000000..7b69db7
--- /dev/null
+++ b/arch/ia64/include/asm/efi.h
@@ -0,0 +1,6 @@
+#ifndef _ASM_EFI_H
+#define _ASM_EFI_H
+
+#include <asm-generic/efi.h>
+
+#endif /* _ASM_EFI_H */
diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index b7388a4..d6eb766 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -9,7 +9,6 @@
 
 #include <linux/efi.h>
 #include <linux/pci.h>
-#include <asm/efi.h>
 #include <asm/setup.h>
 #include <asm/desc.h>
 
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 0062a01..4c8f5c2 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -101,9 +101,14 @@ extern void efi_call_phys_prelog(void);
 extern void efi_call_phys_epilog(void);
 extern void efi_unmap_memmap(void);
 extern void efi_memory_uc(u64 addr, unsigned long size);
+extern void efi_late_init(void);
+extern void efi_free_boot_services(void);
+extern efi_status_t efi_query_variable_store(u32 attributes, unsigned long size);
 
 #ifdef CONFIG_EFI
 
+extern int efi_enabled(int facility);
+
 static inline bool efi_is_native(void)
 {
 	return IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT);
@@ -120,6 +125,11 @@ static inline bool efi_is_native(void)
 #define efi_call4(_f, _a1, _a2, _a3, _a4)		(-ENOSYS)
 #define efi_call5(_f, _a1, _a2, _a3, _a4, _a5)		(-ENOSYS)
 #define efi_call6(_f, _a1, _a2, _a3, _a4, _a5, _a6)	(-ENOSYS)
+
+static inline int efi_enabled(int facility)
+{
+	return 0;
+}
 #endif /* CONFIG_EFI */
 
 #endif /* _ASM_X86_EFI_H */
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index f0de629..415e51b 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -78,7 +78,6 @@
 #include <asm/e820.h>
 #include <asm/mpspec.h>
 #include <asm/setup.h>
-#include <asm/efi.h>
 #include <asm/timer.h>
 #include <asm/i8259.h>
 #include <asm/sections.h>
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index c7e22ab..4fce62a 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -44,7 +44,6 @@
 #include <linux/bcd.h>
 
 #include <asm/setup.h>
-#include <asm/efi.h>
 #include <asm/time.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 40e4469..108a825 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -29,7 +29,6 @@
 #include <asm/page.h>
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
-#include <asm/efi.h>
 
 /*
  * To make EFI call EFI runtime service in physical addressing mode we need
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39a0e7f..de26614 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -35,7 +35,6 @@
 #include <asm/pgtable.h>
 #include <asm/tlbflush.h>
 #include <asm/proto.h>
-#include <asm/efi.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
 
diff --git a/arch/x86/platform/uv/bios_uv.c b/arch/x86/platform/uv/bios_uv.c
index 7666121..f3b1fa1 100644
--- a/arch/x86/platform/uv/bios_uv.c
+++ b/arch/x86/platform/uv/bios_uv.c
@@ -21,7 +21,6 @@
 
 #include <linux/efi.h>
 #include <linux/export.h>
-#include <asm/efi.h>
 #include <linux/io.h>
 #include <asm/uv/bios.h>
 #include <asm/uv/uv_hub.h>
diff --git a/include/asm-generic/efi.h b/include/asm-generic/efi.h
new file mode 100644
index 0000000..8a31713
--- /dev/null
+++ b/include/asm-generic/efi.h
@@ -0,0 +1,17 @@
+#ifndef _ASM_GENERIC_EFI_H
+#define _ASM_GENERIC_EFI_H
+
+static inline void efi_late_init(void) {}
+static inline void efi_free_boot_services(void) {}
+
+static inline efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
+{
+	return EFI_SUCCESS;
+}
+
+static inline int efi_enabled(int facility)
+{
+	return IS_ENABLED(CONFIG_EFI);
+}
+
+#endif /* _ASM_GENERIC_EFI_H */
diff --git a/include/linux/efi.h b/include/linux/efi.h
index 5f8f176..ced7644 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -573,19 +573,6 @@ extern void efi_map_pal_code (void);
 extern void efi_memmap_walk (efi_freemem_callback_t callback, void *arg);
 extern void efi_gettimeofday (struct timespec *ts);
 extern void efi_enter_virtual_mode (void);	/* switch EFI to virtual mode, if possible */
-#ifdef CONFIG_X86
-extern void efi_late_init(void);
-extern void efi_free_boot_services(void);
-extern efi_status_t efi_query_variable_store(u32 attributes, unsigned long size);
-#else
-static inline void efi_late_init(void) {}
-static inline void efi_free_boot_services(void) {}
-
-static inline efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
-{
-	return EFI_SUCCESS;
-}
-#endif
 extern void __iomem *efi_lookup_mapped_addr(u64 phys_addr);
 extern u64 efi_get_iobase (void);
 extern u32 efi_mem_type (unsigned long phys_addr);
@@ -635,22 +622,6 @@ extern int __init efi_setup_pcdp_console(char *);
 #define EFI_MEMMAP		4	/* Can we use EFI memory map? */
 #define EFI_64BIT		5	/* Is the firmware 64-bit? */
 
-#ifdef CONFIG_EFI
-# ifdef CONFIG_X86
-extern int efi_enabled(int facility);
-# else
-static inline int efi_enabled(int facility)
-{
-	return 1;
-}
-# endif
-#else
-static inline int efi_enabled(int facility)
-{
-	return 0;
-}
-#endif
-
 /*
  * Variable Attributes
  */
@@ -842,4 +813,6 @@ int efivars_sysfs_init(void);
 
 #endif /* CONFIG_EFI_VARS */
 
+#include <asm/efi.h>
+
 #endif /* _LINUX_EFI_H */
-- 
1.8.1.4

Re: [PATCH 1/2] efi: Add asm-generic/efi.h for non-x86

[Matt Fleming]

On Thu, 17 Oct, at 01:19:14PM, Matt Fleming wrote:
> From: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> From the #ifdef CONFIG_X86 in linux/efi.h it's clear we need a place to
> declare functions that are implemented differently for each
> architecture.
> 
> Since it's only x86 that needs to do special things, add a generic EFI
> header file that can be used by everyone else and move the x86-specific
> stuff to arch/x86/include/asm/efi.h.
> 
> Because the asm files are now included from linux/efi.h directly, this
> change means we no longer have to include the asm file explicitly from C
> files, allowing us to delete quite a few #include lines.
> 
> Cc: H. Peter Anvin <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
> Cc: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
> Cc: Tony Luck <tony.luck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> Cc: Leif Lindholm <leif.lindholm-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
> Signed-off-by: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---

[...]

> diff --git a/include/asm-generic/efi.h b/include/asm-generic/efi.h
> new file mode 100644
> index 0000000..8a31713
> --- /dev/null
> +++ b/include/asm-generic/efi.h
> @@ -0,0 +1,17 @@
> +#ifndef _ASM_GENERIC_EFI_H
> +#define _ASM_GENERIC_EFI_H
> +
> +static inline void efi_late_init(void) {}
> +static inline void efi_free_boot_services(void) {}
> +
> +static inline efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
> +{
> +	return EFI_SUCCESS;
> +}
> +
> +static inline int efi_enabled(int facility)
> +{
> +	return IS_ENABLED(CONFIG_EFI);
> +}
> +
> +#endif /* _ASM_GENERIC_EFI_H */

After reading Leif's arm runtime patches this patch obviously doesn't
make much sense. I'll work on something better.

-- 
Matt Fleming, Intel Open Source Technology Center

Re: [PATCH 1/2] efi: Add asm-generic/efi.h for non-x86

[Matt Fleming]

On Thu, 17 Oct, at 03:16:53PM, Matt Fleming wrote:
> After reading Leif's arm runtime patches this patch obviously doesn't
> make much sense. I'll work on something better.

OK, since Leif's stuff needs to go through another revision, I'm gonna
leave these patches as-is and merge them into the 'next' branch. I'll
throw some patches at Leif to move efi_enabled() to common code to
include in his series.

-- 
Matt Fleming, Intel Open Source Technology Center

[PATCH v3 2/2] x86/efi: Add EFI framebuffer earlyprintk support

[Matt Fleming]

From: Matt Fleming <matt.fleming@intel.com>

It's incredibly difficult to diagnose early EFI boot issues without
special hardware because earlyprintk=vga doesn't work on EFI systems.

Add support for writing to the EFI framebuffer, via earlyprintk=efi,
which will actually give users a chance of providing debug output.

Cc: H. Peter Anvin <hpa@zytor.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Jones <pjones@redhat.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
---

v3:

 - use white as foreground text colour

v2:

 - add asm/efi.h to efi/early_printk.c for console prototype
 - Kconfig.debug: clear up grammar
 - remove uneeded paranthesis, due to precedence
 - multiply without spaces
 - make char unsigned
 - make 'dst' u32 * and get rid of memcpy()
 - delete mask code and write color directly
 - move efi_x, efi_y to top of file
 - standardize on unsigned int over int
 - s++ on separate line
 - switch ~(u32)0 for -1
 - scroll instead of clearing screen
 - rename early_efi_clear_line() early_efi_clear_scanline()

 Documentation/kernel-parameters.txt  |   8 +-
 arch/x86/Kconfig.debug               |   9 ++
 arch/x86/include/asm/efi.h           |   2 +
 arch/x86/kernel/early_printk.c       |   6 ++
 arch/x86/platform/efi/Makefile       |   1 +
 arch/x86/platform/efi/early_printk.c | 191 +++++++++++++++++++++++++++++++++++
 6 files changed, 214 insertions(+), 3 deletions(-)
 create mode 100644 arch/x86/platform/efi/early_printk.c

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index fcbb736..c07cb09 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -847,6 +847,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	earlyprintk=	[X86,SH,BLACKFIN,ARM]
 			earlyprintk=vga
+			earlyprintk=efi
 			earlyprintk=xen
 			earlyprintk=serial[,ttySn[,baudrate]]
 			earlyprintk=serial[,0x...[,baudrate]]
@@ -860,7 +861,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Append ",keep" to not disable it when the real console
 			takes over.
 
-			Only vga or serial or usb debug port at a time.
+			Only one of vga, efi, serial, or usb debug port can
+			be used at a time.
 
 			Currently only ttyS0 and ttyS1 may be specified by
 			name.  Other I/O ports may be explicitly specified
@@ -874,8 +876,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Interaction with the standard serial driver is not
 			very good.
 
-			The VGA output is eventually overwritten by the real
-			console.
+			The VGA and EFI output is eventually overwritten by
+			the real console.
 
 			The xen output can only be used by Xen PV guests.
 
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 78d91af..b6fe388 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -59,6 +59,15 @@ config EARLY_PRINTK_DBGP
 	  with klogd/syslogd or the X server. You should normally N here,
 	  unless you want to debug such a crash. You need usb debug device.
 
+config EARLY_PRINTK_EFI
+	bool "Early printk via the EFI framebuffer"
+	depends on EFI && EARLY_PRINTK && FONT_SUPPORT
+	---help---
+	  Write kernel log output directly into the EFI framebuffer.
+
+	  This is useful for kernel debugging when your machine crashes very
+	  early before the console code is initialized.
+
 config X86_PTDUMP
 	bool "Export kernel pagetable layout to userspace via debugfs"
 	depends on DEBUG_KERNEL
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 4c8f5c2..485f48c4 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -114,6 +114,8 @@ static inline bool efi_is_native(void)
 	return IS_ENABLED(CONFIG_X86_64) == efi_enabled(EFI_64BIT);
 }
 
+extern struct console early_efi_console;
+
 #else
 /*
  * IF EFI is not configured, have the EFI calls return -ENOSYS.
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index d15f575..2b99124 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -17,6 +17,7 @@
 #include <asm/mrst.h>
 #include <asm/pgtable.h>
 #include <linux/usb/ehci_def.h>
+#include <linux/efi.h>
 
 /* Simple VGA output */
 #define VGABASE		(__ISA_IO_base + 0xb8000)
@@ -234,6 +235,11 @@ static int __init setup_early_printk(char *buf)
 			early_console_register(&early_hsu_console, keep);
 		}
 #endif
+#ifdef CONFIG_EARLY_PRINTK_EFI
+		if (!strncmp(buf, "efi", 3))
+			early_console_register(&early_efi_console, keep);
+#endif
+
 		buf++;
 	}
 	return 0;
diff --git a/arch/x86/platform/efi/Makefile b/arch/x86/platform/efi/Makefile
index 6db1cc4..b7b0b35 100644
--- a/arch/x86/platform/efi/Makefile
+++ b/arch/x86/platform/efi/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_EFI) 		+= efi.o efi_$(BITS).o efi_stub_$(BITS).o
 obj-$(CONFIG_ACPI_BGRT) += efi-bgrt.o
+obj-$(CONFIG_EARLY_PRINTK_EFI)	+= early_printk.o
diff --git a/arch/x86/platform/efi/early_printk.c b/arch/x86/platform/efi/early_printk.c
new file mode 100644
index 0000000..6599a00
--- /dev/null
+++ b/arch/x86/platform/efi/early_printk.c
@@ -0,0 +1,191 @@
+/*
+ * Copyright (C) 2013 Intel Corporation; author Matt Fleming
+ *
+ *  This file is part of the Linux kernel, and is made available under
+ *  the terms of the GNU General Public License version 2.
+ */
+
+#include <linux/console.h>
+#include <linux/efi.h>
+#include <linux/font.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <asm/setup.h>
+
+static const struct font_desc *font;
+static u32 efi_x, efi_y;
+
+static __init void early_efi_clear_scanline(unsigned int y)
+{
+	unsigned long base, *dst;
+	u16 len;
+
+	base = boot_params.screen_info.lfb_base;
+	len = boot_params.screen_info.lfb_linelength;
+
+	dst = early_ioremap(base + y*len, len);
+	if (!dst)
+		return;
+
+	memset(dst, 0, len);
+	early_iounmap(dst, len);
+}
+
+static __init void early_efi_scroll_up(void)
+{
+	unsigned long base, *dst, *src;
+	u16 len;
+	u32 i, height;
+
+	base = boot_params.screen_info.lfb_base;
+	len = boot_params.screen_info.lfb_linelength;
+	height = boot_params.screen_info.lfb_height;
+
+	for (i = 0; i < height - font->height; i++) {
+		dst = early_ioremap(base + i*len, len);
+		if (!dst)
+			return;
+
+		src = early_ioremap(base + (i + font->height) * len, len);
+		if (!src) {
+			early_iounmap(dst, len);
+			return;
+		}
+
+		memmove(dst, src, len);
+
+		early_iounmap(src, len);
+		early_iounmap(dst, len);
+	}
+}
+
+static void early_efi_write_char(u32 *dst, unsigned char c, unsigned int h)
+{
+	const u32 color_black = 0x00000000;
+	const u32 color_white = 0x00ffffff;
+	const u8 *src;
+	u8 s8;
+	int m;
+
+	src = font->data + c * font->height;
+	s8 = *(src + h);
+
+	for (m = 0; m < 8; m++) {
+		if ((s8 >> (7 - m)) & 1)
+			*dst = color_white;
+		else
+			*dst = color_black;
+		dst++;
+	}
+}
+
+static __init void
+early_efi_write(struct console *con, const char *str, unsigned int num)
+{
+	struct screen_info *si;
+	unsigned long base;
+	unsigned int len;
+	const char *s;
+	void *dst;
+
+	base = boot_params.screen_info.lfb_base;
+	si = &boot_params.screen_info;
+	len = si->lfb_linelength;
+
+	while (num) {
+		unsigned int linemax;
+		unsigned int h, count = 0;
+
+		for (s = str; *s && *s != '\n'; s++) {
+			if (count == num)
+				break;
+			count++;
+		}
+
+		linemax = (si->lfb_width - efi_x) / font->width;
+		if (count > linemax)
+			count = linemax;
+
+		for (h = 0; h < font->height; h++) {
+			unsigned int n, x;
+
+			dst = early_ioremap(base + (efi_y + h) * len, len);
+			if (!dst)
+				return;
+
+			s = str;
+			n = count;
+			x = efi_x;
+
+			while (n-- > 0) {
+				early_efi_write_char(dst + x*4, *s, h);
+				x += font->width;
+				s++;
+			}
+
+			early_iounmap(dst, len);
+		}
+
+		num -= count;
+		efi_x += count * font->width;
+		str += count;
+
+		if (num > 0 && *s == '\n') {
+			efi_x = 0;
+			efi_y += font->height;
+			str++;
+			num--;
+		}
+
+		if (efi_x >= si->lfb_width) {
+			efi_x = 0;
+			efi_y += font->height;
+		}
+
+		if (efi_y + font->height >= si->lfb_height) {
+			u32 i;
+
+			efi_y -= font->height;
+			early_efi_scroll_up();
+
+			for (i = 0; i < font->height; i++)
+				early_efi_clear_scanline(efi_y + i);
+		}
+	}
+}
+
+static __init int early_efi_setup(struct console *con, char *options)
+{
+	struct screen_info *si;
+	u16 xres, yres;
+	u32 i;
+
+	si = &boot_params.screen_info;
+	xres = si->lfb_width;
+	yres = si->lfb_height;
+
+	/*
+	 * early_efi_write_char() implicitly assumes a framebuffer with
+	 * 32-bits per pixel.
+	 */
+	if (si->lfb_depth != 32)
+		return -ENODEV;
+
+	font = get_default_font(xres, yres, -1, -1);
+	if (!font)
+		return -ENODEV;
+
+	efi_y = rounddown(yres, font->height) - font->height;
+	for (i = 0; i < (yres - efi_y) / font->height; i++)
+		early_efi_scroll_up();
+
+	return 0;
+}
+
+struct console early_efi_console = {
+	.name =		"earlyefi",
+	.write =	early_efi_write,
+	.setup =	early_efi_setup,
+	.flags =	CON_PRINTBUFFER,
+	.index =	-1,
+};
-- 
1.8.1.4