@@ -1073,9 +1073,16 @@
specified address. The serial port must already be
setup and configured. Options are not yet supported.
+ efi[,options] # arm64 or x86
+ Start an early, unaccelerated console on the EFI
+ framebuffer. On DMA coherent arm64 systems that use
+ system memory for the framebuffer, pass the 'ram'
+ option so that it is mapped with the correct
+ attributes.
+
earlyprintk= [X86,SH,ARM,M68k,S390]
earlyprintk=vga
- earlyprintk=efi
+ earlyprintk=efi # x86 only
earlyprintk=sclp
earlyprintk=xen
earlyprintk=serial[,ttySn[,baudrate]]
@@ -11,6 +11,7 @@
#include <asm/neon.h>
#include <asm/ptrace.h>
#include <asm/tlbflush.h>
+#include <linux/screen_info.h>
#ifdef CONFIG_EFI
extern void efi_init(void);
@@ -149,4 +150,9 @@ static inline void efi_set_pgd(struct mm_struct *mm)
void efi_virtmap_load(void);
void efi_virtmap_unload(void);
+static inline struct screen_info *efi_get_screen_info(void)
+{
+ return &screen_info;
+}
+
#endif /* _ASM_EFI_H */
@@ -201,4 +201,5 @@ config EFI_DEV_PATH_PARSER
config UEFI_EARLYCON
bool
+ default y if ARM64
select FONT_SUPPORT
@@ -10,13 +10,17 @@
#include <linux/font.h>
#include <linux/io.h>
#include <linux/kernel.h>
+#include <linux/serial_core.h>
#include <asm/efi.h>
static const struct font_desc *font;
static u32 efi_x, efi_y;
static void *efi_fb;
static bool early_efi_keep;
+static bool fb_is_ram;
+static u64 fb_base;
+#ifdef CONFIG_EARLY_PRINTK_EFI
/*
* efi earlyprintk need use early_ioremap to map the framebuffer.
* But early_ioremap is not usable for earlyprintk=efi,keep, ioremap should
@@ -40,6 +44,7 @@ static __init int early_efi_map_fb(void)
return efi_fb ? 0 : -ENOMEM;
}
early_initcall(early_efi_map_fb);
+#endif
/*
* early_efi_map maps efi framebuffer region [start, start + len -1]
@@ -48,21 +53,21 @@ early_initcall(early_efi_map_fb);
*/
static __ref void *early_efi_map(unsigned long start, unsigned long len)
{
- u64 base;
-
- base = efi_get_screen_info()->lfb_base;
- if (efi_get_screen_info()->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
- base |= (u64)efi_get_screen_info()->ext_lfb_base << 32;
-
if (efi_fb)
return (efi_fb + start);
+ else if (fb_is_ram)
+ return early_memremap(fb_base + start, len);
else
- return early_ioremap(base + start, len);
+ return early_ioremap(fb_base + start, len);
}
static __ref void early_efi_unmap(void *addr, unsigned long len)
{
- if (!efi_fb)
+ if (efi_fb)
+ return;
+ if (fb_is_ram)
+ early_memunmap(addr, len);
+ else
early_iounmap(addr, len);
}
@@ -210,6 +215,10 @@ static __init int early_efi_setup(struct console *con, char *options)
xres = si->lfb_width;
yres = si->lfb_height;
+ fb_base = efi_get_screen_info()->lfb_base;
+ if (efi_get_screen_info()->capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+ fb_base |= (u64)efi_get_screen_info()->ext_lfb_base << 32;
+
/*
* early_efi_write_char() implicitly assumes a framebuffer with
* 32-bits per pixel.
@@ -226,11 +235,12 @@ static __init int early_efi_setup(struct console *con, char *options)
early_efi_scroll_up();
/* early_console_register will unset CON_BOOT in case ,keep */
- if (!(con->flags & CON_BOOT))
+ if (con && !(con->flags & CON_BOOT))
early_efi_keep = true;
return 0;
}
+#ifdef CONFIG_EARLY_PRINTK_EFI
struct console early_efi_console = {
.name = "earlyefi",
.write = early_efi_write,
@@ -238,3 +248,17 @@ struct console early_efi_console = {
.flags = CON_PRINTBUFFER,
.index = -1,
};
+#endif
+
+static int __init efi_earlycon_setup(struct earlycon_device *device,
+ const char *opt)
+{
+ if (efi_get_screen_info()->orig_video_isVGA != VIDEO_TYPE_EFI)
+ return -ENODEV;
+
+ device->con->write = early_efi_write;
+ early_efi_setup(NULL, NULL);
+ fb_is_ram = !strcmp(opt, "ram");
+ return 0;
+}
+EARLYCON_DECLARE(efi, efi_earlycon_setup);
This repurposes the existing EFI earlyprintk support and exposes it as an earlycon implementation, which can be enabled by passing the kernel parameter 'earlycon=efi' on the command line. Note that the early console is initialized before we have discovered anything about the memory map, and so we cannot determine automatically whether the framebuffer is backed by system memory that must be mapped with cacheable attributes. So instead, a 'ram' earlycon option is implemented to force this manually. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- Documentation/admin-guide/kernel-parameters.txt | 9 ++++- arch/arm64/include/asm/efi.h | 6 +++ drivers/firmware/efi/Kconfig | 1 + drivers/firmware/efi/earlycon.c | 42 +++++++++++++++----- 4 files changed, 48 insertions(+), 10 deletions(-)