From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Sverdlin Subject: Re: [PATCH] i2c: davinci: Fix bus rate calculation on Keystone SoC Date: Thu, 18 Jun 2015 13:30:58 +0200 Message-ID: <5582ABF2.4090308@nokia.com> References: <5582870B.7030304@nokia.com> <558288B0.1020706@ti.com> <55828ADB.3080604@nokia.com> <55828E7F.8060501@ti.com> <55829159.8050707@nokia.com> <558293C9.9050904@ti.com> <558297B3.2060406@nokia.com> <5582A7AF.5030000@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5582A7AF.5030000-l0cyMroinI0@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: ext Sekhar Nori , Kevin Hilman , Wolfram Sang , linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Murali Karicheri List-Id: linux-i2c@vger.kernel.org Hello! On 18/06/15 13:12, ext Sekhar Nori wrote: >>>> Ah, beyond the evalboards, there are device-trees not linked into the kernel, >>>>> >>>> but flashed into the boards, as originally in OF. They are part of the HW, its >>>>> >>>> description. Not part or description of the Kernel. And you have no way to >>>>> >>>> introduce this fix any more without updating this OF part if you go with >>>>> >>>> new compatible property. >>> >> I see. So how critical is this fix? That should be described in the >>> >> commit description. And if its really critical, stable kernel should be >>> >> CCed too. >> > >> > Now we got to the point, see below... >> > >>>>>>>>>>> >>>>>>>>>> And from the other PoV, device-trees are for something one cannot probe. We >>>>>>>>>>> >>>>>>>>>> can probe for Keystone revisions and can free the end-user from this headache >>>>>>>>>>> >>>>>>>>>> completely. >>>>>>> >>>>>> Keep in mind that this can invite driver patching whenever version >>>>>>> >>>>>> number is tinkered with in hardware - even for otherwise >>>>>>> >>>>>> software-invsible changes. >>>>> >>>> >>>>> >>>> That's true. But I do not have an overview, how many IP versions do you actually have? >>>>> >>>> I've found one revision in Davinci manual, one revision in Keystone manual, even >>>>> >>>> including minor revision. Checking only major revision now can survive couple of minor >>>>> >>>> changes in IP. >>> >> Yeah, sticking to major version should help. What I am worried about are >>> >> versions coming in future, not those existing. And development on >>> >> keystone architecture is ongoing in TI. >> > >> > This is not really critical fix. Currently bus rate is lower than expected because of these >> > calculation errors. The fix maximizes the bus rate. So newer SoCs will run little bit slower >> > until support is added to this part of the code. Not really critical. So no point in CCing >> > stable maintainers also. > If its not a critical fix, do we really need to care about older DTBs > which have been ROM'ed into production? I tend not to change the DT binding, but if majority will decide it's the way to go, I'll prepare another patch. Let's wait for other opinions... -- Best regards, Alexander Sverdlin.