From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nishanth Menon Subject: Re: [PM][PATCH v3 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access Date: Thu, 6 May 2010 05:44:27 -0500 Message-ID: <4BE29D8B.2070403@ti.com> References: <1271097933-22981-1-git-send-email-nm@ti.com> <87d3x9ykdf.fsf@deeprootsystems.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from bear.ext.ti.com ([192.94.94.41]:42508 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751957Ab0EFKog (ORCPT ); Thu, 6 May 2010 06:44:36 -0400 In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Govindraj Cc: "Kattungal, Deepak" , Kevin Hilman , linux-omap , "Raja, Govindraj" , Tero Kristo Govindraj had written, on 05/06/2010 04:54 AM, the following: > On Thu, May 6, 2010 at 5:49 AM, Kattungal, Deepak wrote: >> Hi Kevin, >> >> My Comments as below. >> >> Regards >> Deepak >> >> -----Original Message----- >> From: Kevin Hilman [mailto:khilman@deeprootsystems.com] >> Sent: Wednesday, May 05, 2010 6:55 PM >> To: Menon, Nishanth >> Cc: linux-omap; Kattungal, Deepak; Raja, Govindraj; Tero Kristo >> Subject: Re: [PM][PATCH v3 2/4] OMAP3: Serial: Errata i202: fix for MDR1 access >> >> Nishanth Menon writes: >> >>> From: Deepak K >>> >>> Original patch: >>> http://git.omapzoom.org/?p=kernel/omap.git;a=commitdiff;h=42d4a342c009bd9727c100abc8a4bc3063c22f0c >>> >>> Errata i202 (OMAP3430 - 1.12, OMAP3630 - 1.6): >> This workaround is currently done for all OMAPs. >> >> Presumably, this errata will eventually be fixed. So, as with other >> errata fixes, we need some sort of SoC-rev based flag and the errata >> workaround done based on that flag. >> >> Deepak : This would be a good fix, thanks for the suggestion. >> >> Also, shouldn't there be a fix for this in the 8250 and omap-serial >> drivers too? >> >> >> Deepak : The 8250 is not using the MDR Register. This would be needed only by the omap-serial. The 8250 being a general driver we may not require the access to MDR1 register. Hence the fix not required for 8250. >> > > Why do you say this fix is not necessary for 8250? drivers/serial/8250.c does not use mdr register. it does not make sense for a generic driver like this to have OMAP specific register access. > > Isn't the omap_uart_reset configuring uart for 16x mode? > > Context save and restore is an common for whether it is 8250 or omap-serial.c ack. > > The only difference here wrt to MDR and 8250 is > -> MDR though not accesed by 8250 currently serial.c sets it to uart16x mode. > > In omap-serial.c we configure MDR based on baudrate as we have an uart13x mode > which is ignored in 8250 and thus 8250 may not support 13x baud's correctly > which is taken care in omap-serial. given that MDR register deals with mostly IRDA settings, i am curious to see how omap-serial hits on a shared register here :). > > I think this patch is fine and only concern is to make it applicable > to appropriate socs as kevin said. Sure. trivial to do. Could you comment on the proposal i posted earlier? -- Regards, Nishanth Menon