linux-kernel - Re: [PATCH] efi earlyprintk fix

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Date:	Sat, 9 Nov 2013 11:44:29 +0800
From:	Dave Young <dyoung@...hat.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	matt.fleming@...el.com, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efi earlyprintk fix

On 11/08/13 at 10:36am, Matt Fleming wrote:
> On Thu, 07 Nov, at 08:09:06PM, Dave Young wrote:
> > Here is my debug message about the efifb params (all hex values):
> > [    0.000000] efi fb lfb width: 280
> > [    0.000000] efi fb lfb height: 1e0
> > [    0.000000] efi fb lfb base: e0000000
> > [    0.000000] efi fb lfb linelength: a00
> > [    0.000000] efi fb font height: 10
> > [    0.000000] efi fb font width: 8
> > 
> > The problem looks related to the pr_cont(), here is what I observed:
> > [    0.000000] efi: EFI v2.00 by Lenovo
> >                     ACPI=0xdabfe000  ACPI 2.0=0xdabfe014  SMBIOS=0xdaa9e000
> > [    0.000000] efi: 
> > 
> > After relooking the code, below fix is more reasonable than my original one,
> > But I still confused why it only happens on this machine.
> 
> Dave, could you try this patch?

Hi, Matt

Confirmed, your patch work ok for the pr_cont issue.

Actually I mixed two problems in my report, one is there's always one blank line
at the bottom of screen, the other is the pr_cont issue. For the second problem
change >= to > looks better. For the previous problem still need to move the
hunk below to the beginning point of early_efi_write function. It just works for me
but I'm not sure why this is not necessary for other machines. 

+		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);
+		}


> 
> ---
> 
> diff --git a/arch/x86/platform/efi/early_printk.c b/arch/x86/platform/efi/early_printk.c
> index 6599a0027b76..81b506d5befd 100644
> --- a/arch/x86/platform/efi/early_printk.c
> +++ b/arch/x86/platform/efi/early_printk.c
> @@ -142,7 +142,7 @@ early_efi_write(struct console *con, const char *str, unsigned int num)
>  			efi_y += font->height;
>  		}
>  
> -		if (efi_y + font->height >= si->lfb_height) {
> +		if (efi_y + font->height > si->lfb_height) {
>  			u32 i;
>  
>  			efi_y -= font->height;
> -- 
> Matt Fleming, Intel Open Source Technology Center
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