linux-kernel - Re: [PATCH v2 1/1] x86/early_printk: Use _

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Message-ID: <alpine.DEB.2.11.1510121106010.6097@nanos>
Date:	Mon, 12 Oct 2015 11:11:50 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org
Subject: Re: [PATCH v2 1/1] x86/early_printk: Use __iomem address space for
 IO

On Mon, 12 Oct 2015, Andy Shevchenko wrote:
> On Sun, 2015-10-11 at 21:18 +0200, Thomas Gleixner wrote:
> > Andy,
> > 
> > On Fri, 9 Oct 2015, Andy Shevchenko wrote:
> > >  #ifdef CONFIG_PCI
> > >  static void mem32_serial_out(unsigned long addr, int offset, int 
> > value)
> > >  {
> > > -     u32 *vaddr = (u32 *)addr;
> > > +     void __iomem *vaddr = (void __iomem *)addr;
> > >       /* shift implied by pointer type */
> > >       writel(value, vaddr + offset);
> > 
> > This is broken. Assume vaddr = 0x1000 and offset = 1
> 
> Yes, I noticed in reply to myself  
> http://www.spinics.net/lists/kernel/msg2094143.html
> 
> Tests were okay because platform I have is using 8-bit I/O.
> 
> Does it make sense to use the following approach?
> 
>  void __iomem *vaddr = (void __iomem *)addr;
>  writel(value, vaddr + offset << 2);

What's wrong with: u32 __iomem *vaddr ?

Thanks,

	tglx


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