linux-kernel - Re: [PATCH] ignore ,keep for efi earlyprintk

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Date:	Tue, 29 Apr 2014 10:45:39 +0100
From:	Matt Fleming <matt@...sole-pimps.org>
To:	Dave Young <dyoung@...hat.com>
Cc:	matt.fleming@...el.com, hpa@...or.com, akpm@...ux-foundation.org,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: Re: [PATCH] ignore ,keep for efi earlyprintk

On Sat, 26 Apr, at 03:28:21PM, Dave Young wrote:
> 
> There's other kernel messages without appending ,keep.
> 
> Also console=ttyS0 does not work with earlyprintk=efi,keep, removing
> ,keep it works well.

Try console=efi

> > > Actually efi earlyprintk is using __init functions such as early_ioremap etc.
> > > Thus efi earlyconsole can not be kept.
> >  
> > Urgh, good point, that's a bug. However I'm sure I've had this working
> > in the past and have in fact used it to debug stuff.
> > 
> > Could you try and fix this up so it works with 'keep'?
> 
> Will do. I want use ioremap when it is available but it's hard to decide
> where to add the code.
> 
> I'm thinking to do below:
> 1. ioremap the whole framebuffer like: efi_fb = ioremap(lfb_base, lfb_size) in the
>    function efi_enter_virtual_mode because ioremap should be usable then.
> 
> 2. add two functions for earlyprintk use (scrollup, write, etc.) 
> __init_refok void * get_vaddr(unsigned long start, unsigned long len)
> {
> 	unsigned long base;
> 
> 	base = boot_params.screen_info.lfb_base;
> 	if (efi_fb)
> 		return (efi_fb + start - base);
> 	else
> 		return early_ioremap(start, len);
> }
> 
> __init_refok void put_vaddr(void *addr, unsigned long len)
> {
> 	if (!efi_fb)
> 		early_iounmap(addr, len);
> }
> 
> But it does not sound good to add the ioremap in enter virtual mode funtion.   
> 
> Please help if you have any other better idea.

I would just replace the existing calls to early_ioremap() with
efi_ioremap() and implement it like so (all in
arch/x86/platform/efi/early_printk.c),

static void *efi_ioremap(resource_size_t phys_addr, unsigned long size)
{
	if (system_state == SYSTEM_BOOTING)
		return early_ioremap(phys_addr, size);

	return ioremap(phys_addr, size);
}

At least I think SYSTEM_BOOTING is the correct way to figure out when to
use early_ioremap(), I'm open to other suggestions though.

-- 
Matt Fleming, Intel Open Source Technology Center
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