Commit b418d660 authored by Andy Shevchenko's avatar Andy Shevchenko Committed by Ingo Molnar
Browse files

efi/earlycon: Remap entire framebuffer after page initialization 



When commit:

  69c1f396 ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation")

moved the x86 specific EFI earlyprintk implementation to a shared location,
it also tweaked the behaviour. In particular, it dropped a trick with full
framebuffer remapping after page initialization, leading to two regressions:

  1) very slow scrolling after page initialization,
  2) kernel hang when the 'keep_bootcon' command line argument is passed.

Putting the tweak back fixes #2 and mitigates #1, i.e., it limits the slow
behavior to the early boot stages, presumably due to eliminating heavy
map()/unmap() operations per each pixel line on the screen.

 [ ardb: ensure efifb is unmapped again unless keep_bootcon is in effect. ]
 [ mingo: speling fixes. ]

Signed-off-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarArd Biesheuvel <ardb@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Bhupesh Sharma <bhsharma@redhat.com>
Cc: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Cc: linux-efi@vger.kernel.org
Fixes: 69c1f396 ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation")
Link: https://lkml.kernel.org/r/20191206165542.31469-7-ardb@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 9fa76ca7

drivers/firmware/efi/earlycon.c

+40 −0
Original line number Diff line number Diff line
@@ -13,18 +13,57 @@ 


#include <asm/early_ioremap.h>



static const struct console *earlycon_console __initdata;

static const struct font_desc *font;

static u32 efi_x, efi_y;

static u64 fb_base;

static pgprot_t fb_prot;

static void *efi_fb;



/*

 * EFI earlycon needs to use early_memremap() to map the framebuffer.

 * But early_memremap() is not usable for 'earlycon=efifb keep_bootcon',

 * memremap() should be used instead. memremap() will be available after

 * paging_init() which is earlier than initcall callbacks. Thus adding this

 * early initcall function early_efi_map_fb() to map the whole EFI framebuffer.

 */

static int __init efi_earlycon_remap_fb(void)

{

	/* bail if there is no bootconsole or it has been disabled already */

	if (!earlycon_console || !(earlycon_console->flags & CON_ENABLED))

		return 0;



	if (pgprot_val(fb_prot) == pgprot_val(PAGE_KERNEL))

		efi_fb = memremap(fb_base, screen_info.lfb_size, MEMREMAP_WB);

	else

		efi_fb = memremap(fb_base, screen_info.lfb_size, MEMREMAP_WC);



	return efi_fb ? 0 : -ENOMEM;

}

early_initcall(efi_earlycon_remap_fb);



static int __init efi_earlycon_unmap_fb(void)

{

	/* unmap the bootconsole fb unless keep_bootcon has left it enabled */

	if (efi_fb && !(earlycon_console->flags & CON_ENABLED))

		memunmap(efi_fb);

	return 0;

}

late_initcall(efi_earlycon_unmap_fb);



static __ref void *efi_earlycon_map(unsigned long start, unsigned long len)

{

	if (efi_fb)

		return efi_fb + start;



	return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot));

}



static __ref void efi_earlycon_unmap(void *addr, unsigned long len)

{

	if (efi_fb)

		return;



	early_memunmap(addr, len);

}
@@ -201,6 +240,7 @@ static int __init efi_earlycon_setup(struct earlycon_device *device, 
		efi_earlycon_scroll_up();



	device->con->write = efi_earlycon_write;

	earlycon_console = device->con;

	return 0;

}

EARLYCON_DECLARE(efifb, efi_earlycon_setup);

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