From mboxrd@z Thu Jan 1 00:00:00 1970 From: felipe.contreras@gmail.com (Felipe Contreras) Date: Mon, 14 Sep 2009 17:38:32 +0300 Subject: [PATCH] arm: remove unused code in delay.S In-Reply-To: <20090914140059.GC21580@n2100.arm.linux.org.uk> References: <1252875960-21512-1-git-send-email-felipe.contreras@gmail.com> <200909132328.47079.marek.vasut@gmail.com> <20090913230008.GC30169@n2100.arm.linux.org.uk> <20090914002100.GD30621@shareable.org> <20090914081001.GB14519@n2100.arm.linux.org.uk> <94a0d4530909140558nd8d2c47lc9954563c80a574f@mail.gmail.com> <20090914140059.GC21580@n2100.arm.linux.org.uk> Message-ID: <94a0d4530909140738t7e4d646r134cfd884da21348@mail.gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Sep 14, 2009 at 5:00 PM, Russell King - ARM Linux 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 >> 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