linux-kernel - Re: [PATCH v2 2/7] x86/boot: Introduce helpers for serial I/O

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Message-ID: <20190328135226.GB9224@smile.fi.intel.com>
Date:   Thu, 28 Mar 2019 15:52:26 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/7] x86/boot: Introduce helpers for serial I/O

On Thu, Mar 28, 2019 at 02:28:55PM +0100, Borislav Petkov wrote:
> On Thu, Mar 28, 2019 at 03:11:40PM +0200, Andy Shevchenko wrote:
> > Any idea how it can be done?
> 
> Like this?
> 
> static u8 serial_inb(unsigned long addr, int offset)

It's not a generic serial_in()...

> {
> 	if (early_serial_do_mmio) {
> 		asm volatile("movb %1,%0" : "=q" (v) : "m" (*(volatile u8 __force *)addr));
> 
> 		return v;
> 	} else {
> 		 return inb(addr + offset);
> 	}
> }

What about mmio32 as next step?

Do we have to "fix" earlyprintk implementation in kernel to do the same?

-- 
With Best Regards,
Andy Shevchenko