From: Arvind Sankar nivedita@alum.mit.edu
[ Upstream commit d92b54570d24d017d2630e314b525ed792f5aa6c ]
On x86, until PAT is initialized, WC translates into UC-. Since we calculate and store pgprot_writecombine(PAGE_KERNEL) when earlycon is initialized, this means we actually use UC- mappings instead of WC mappings, which makes scrolling very slow.
Instead store a boolean flag to indicate whether we want to use writeback or write-combine mappings, and recalculate the actual pgprot_t we need on every mapping. Once PAT is initialized, we will start using write-combine mappings, which speeds up the scrolling considerably.
Signed-off-by: Arvind Sankar nivedita@alum.mit.edu Signed-off-by: Ard Biesheuvel ardb@kernel.org Cc: Hans de Goede hdegoede@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-efi@vger.kernel.org Fixes: 69c1f396f25b ("efi/x86: Convert x86 EFI earlyprintk into generic earlycon implementation") Link: https://lkml.kernel.org/r/20191224132909.102540-2-ardb@kernel.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/firmware/efi/earlycon.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/drivers/firmware/efi/earlycon.c b/drivers/firmware/efi/earlycon.c index d4077db6dc97f..5d4f84781aa03 100644 --- a/drivers/firmware/efi/earlycon.c +++ b/drivers/firmware/efi/earlycon.c @@ -17,7 +17,7 @@ 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 bool fb_wb; static void *efi_fb;
/* @@ -33,10 +33,8 @@ static int __init efi_earlycon_remap_fb(void) 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); + efi_fb = memremap(fb_base, screen_info.lfb_size, + fb_wb ? MEMREMAP_WB : MEMREMAP_WC);
return efi_fb ? 0 : -ENOMEM; } @@ -53,9 +51,12 @@ late_initcall(efi_earlycon_unmap_fb);
static __ref void *efi_earlycon_map(unsigned long start, unsigned long len) { + pgprot_t fb_prot; + if (efi_fb) return efi_fb + start;
+ fb_prot = fb_wb ? PAGE_KERNEL : pgprot_writecombine(PAGE_KERNEL); return early_memremap_prot(fb_base + start, len, pgprot_val(fb_prot)); }
@@ -215,10 +216,7 @@ static int __init efi_earlycon_setup(struct earlycon_device *device, if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE) fb_base |= (u64)screen_info.ext_lfb_base << 32;
- if (opt && !strcmp(opt, "ram")) - fb_prot = PAGE_KERNEL; - else - fb_prot = pgprot_writecombine(PAGE_KERNEL); + fb_wb = opt && !strcmp(opt, "ram");
si = &screen_info; xres = si->lfb_width;