From: Vinod Koul <vinod.koul@intel.com>
To: Clemens Ladisch <clemens@ladisch.de>
Cc: "Subhransu S. Prusty" <subhransu.s.prusty@intel.com>,
hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86_64: Add memcpy32_toio to write to PCI MMIO
Date: Tue, 16 Sep 2014 20:59:03 +0530 [thread overview]
Message-ID: <20140916152903.GR3131@intel.com> (raw)
In-Reply-To: <540EB3CE.6010700@ladisch.de>
On Tue, Sep 09, 2014 at 10:01:18AM +0200, Clemens Ladisch wrote:
> Subhransu S. Prusty wrote:
> > This is needed because the hardware
>
> Which hardware? Every x86-64 CPU ever built by AMD, Intel, and VIA?
Baytrail and few other SoCs
>
> > does not support 64-bit moveq insructions while writing to PCI MMIO.
>
> > +#ifndef CONFIG_X86_64
> > +#define MEMCPY_TOIO memcpy_toio
> > +#else
> > +#define MEMCPY_TOIO memcpy32_toio
> > +#endif
>
> This does not change any code that uses memcpy_toio().
So the devices cant do 64bit memcpy_toio so we are forced to use 32bit
copies only. This given us such an option
>
> > + for (i = 0; i < count/sizeof(u32); i++)
> > + writel(*src_32++, dst_32++);
>
> This breaks when count is not a multiple of four.
Ah yes, we can fix that
--
~Vinod
prev parent reply other threads:[~2014-09-16 15:54 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-08 8:14 [PATCH] x86_64: Add memcpy32_toio to write to PCI MMIO Subhransu S. Prusty
2014-09-09 8:01 ` Clemens Ladisch
2014-09-16 15:29 ` Vinod Koul [this message]
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