From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Valentine Barshak <vbarshak@ru.mvista.com>
Cc: linuxppc-dev@ozlabs.org, sr@denx.de
Subject: Re: [RFC] [PATCH] PowerPC: Workaround for the 440EP(x)/GR(x) processors identical PVR issue.
Date: Fri, 26 Oct 2007 06:44:11 +1000 [thread overview]
Message-ID: <1193345051.7018.15.camel@pasglop> (raw)
In-Reply-To: <20071025181640.GA18933@ru.mvista.com>
On Thu, 2007-10-25 at 22:16 +0400, Valentine Barshak wrote:
> PowerPC 440EP(x) 440GR(x) processors have the same PVR values, since
> they have identical cores. However, FPU is not supported on GR(x) and
> enabling APU instruction broadcast in the CCR0 register (to enable FPU)
> may cause unpredictable results. There's no safe way to detect FPU
> support at runtime. This patch provides a workarund for the issue.
> We use a POWER6 "logical PVR approach". First, we identify all EP(x)
> and GR(x) processors as GR(x) ones (which is safe). Then we check
> the device tree cpu path. If we have a EP(x) processor entry,
> we call identify_cpu again with PVR | 0x8. This bit is always 0
> in the real PVR. This way we enable FPU only for 440EP(x).
>
> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Why not just or-in the FPU feature bit ?
Ben.
next prev parent reply other threads:[~2007-10-25 20:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-10-25 18:16 [RFC] [PATCH] PowerPC: Workaround for the 440EP(x)/GR(x) processors identical PVR issue Valentine Barshak
2007-10-25 20:44 ` Benjamin Herrenschmidt [this message]
2007-10-26 11:05 ` Valentine Barshak
2007-10-26 11:25 ` Benjamin Herrenschmidt
2007-10-26 13:16 ` Valentine Barshak
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