Messages in this thread | | | Date | Mon, 14 Sep 2009 17:38:32 +0300 | Subject | Re: [PATCH] arm: remove unused code in delay.S | From | Felipe Contreras <> |
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On Mon, Sep 14, 2009 at 5:00 PM, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > On Mon, Sep 14, 2009 at 03:58:24PM +0300, Felipe Contreras wrote: >> On Mon, Sep 14, 2009 at 11:10 AM, Russell King - ARM Linux >> <linux@arm.linux.org.uk> wrote: >> > On Mon, Sep 14, 2009 at 01:21:00AM +0100, Jamie Lokier wrote: >> >> Russell King - ARM Linux wrote: >> >> > On Sun, Sep 13, 2009 at 11:28:47PM +0200, Marek Vasut wrote: >> >> > > > bhi __delay >> >> > > > mov pc, lr >> >> > > > ENDPROC(__udelay) >> >> > > > >> >> > > Hi >> >> > > >> >> > > why was this code there in the first place ? >> >> > >> >> > To make the delay loop more stable and predictable on older CPUs. >> >> >> >> So why has it been commented out, if it's needed for that? >> > >> > We moved on and it penalises later CPUs, leading to udelay providing >> > shorter delays than requested. >> > >> > So the choice was either stable and predictable on older CPUs but >> > buggy on newer CPUs, or correct on all CPUs but gives unnecessarily >> > longer delays on older CPUs. >> >> Why not add an #ifdef CPU_V4 or whatever? > > Because then you get it whenever you configure for V4 as the lowest > denominator CPU, which leads to the buggy behaviour on better CPUs. > It's far better to leave it as is and just accept that the old CPUs > will have longer than necessary delays. If people really really > care (and there's likely to only be a small minority of them now) > changing the '0' to a '1' is a very simple change for them to carry > in their local tree. Unlike getting the right unrolling etc.
Well, they can also 'git revert' this patch. If somebody really cares I think they should shout now and provide a better patch, otherwise this one should be merged.
-- Felipe Contreras -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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