From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Jarzmik Subject: Re: [PATCH v2 1/3] net: irda: pxaficp_ir: use sched_clock() for time management Date: Wed, 16 Sep 2015 11:34:01 +0200 Message-ID: <87eghyso6u.fsf@belgarion.home> References: <1442058324-9760-1-git-send-email-robert.jarzmik@free.fr> <20150915.164025.1543038793305792029.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain Cc: samuel@sortiz.org, petr.cvek@tul.cz, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, arnd@arndb.de To: David Miller Return-path: In-Reply-To: <20150915.164025.1543038793305792029.davem@davemloft.net> (David Miller's message of "Tue, 15 Sep 2015 16:40:25 -0700 (PDT)") Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org David Miller writes: > From: Robert Jarzmik > Date: Sat, 12 Sep 2015 13:45:22 +0200 > >> Instead of using directly the OS timer through direct register access, >> use the standard sched_clock(), which will end up in OSCR reading >> anyway. >> >> This is a first step for direct access register removal and machine >> specific code removal from this driver. >> >> Signed-off-by: Robert Jarzmik > > What is the granularity of the OSCR register? It's 307ns (ie. 3.25MHz clock). > If it is not nanoseconds, then you need to adjust calculations > such as this one: Tell me if the 307ns requires something I should adjust. My understanding is that the flow will be : sched_clock() rd->read_sched_clock() (cyc_to_ns() transformed for return) pxa_read_sched_clock() readl_relaxed(OSCR) I didn't see any timings issue, as the flow looks equivalent to the readl(OSCR), but I might have overlooked something. Cheers. -- Robert