Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753099AbaBYJsI (ORCPT ); Tue, 25 Feb 2014 04:48:08 -0500 Received: from metis.ext.pengutronix.de ([92.198.50.35]:45336 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752505AbaBYJsG (ORCPT ); Tue, 25 Feb 2014 04:48:06 -0500 Message-ID: <1393321661.4156.2.camel@pizza.hi.pengutronix.de> Subject: Re: [PATCH v2 0/6] ARM: STi reset controller support From: Philipp Zabel To: srinivas kandagatla Cc: Maxime Coquelin , Mark Rutland , devicetree@vger.kernel.org, Russell King , kernel@stlinux.com, Pawel Moll , Ian Campbell , Olof Johansson , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, stephen.gallimore@st.com, Rob Herring , Arnd Bergmann , Rob Landley , Kumar Gala , Grant Likely , linux-arm-kernel@lists.infradead.org Date: Tue, 25 Feb 2014 10:47:41 +0100 In-Reply-To: <530C5D8C.1080809@st.com> References: <1389696613-19683-1-git-send-email-srinivas.kandagatla@st.com> <1391437665-11913-1-git-send-email-srinivas.kandagatla@st.com> <1391592486.11239.4.camel@pizza.hi.pengutronix.de> <52F4D76F.8070301@st.com> <5304B849.2080806@st.com> <1393237988.3091.14.camel@pizza.hi.pengutronix.de> <530B514A.4070209@st.com> <1393254982.3091.44.camel@pizza.hi.pengutronix.de> <530C5D8C.1080809@st.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:6f8:1178:2:ca9c:dcff:febd:f1b5 X-SA-Exim-Mail-From: p.zabel@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Srinivas, Am Dienstag, den 25.02.2014, 09:08 +0000 schrieb srinivas kandagatla: > On 24/02/14 15:16, Philipp Zabel wrote: > > Hi Srinivas, > > > > Am Montag, den 24.02.2014, 14:03 +0000 schrieb srinivas kandagatla: > >> Thanks Philipp for your comments, > >> > >> On 24/02/14 10:33, Philipp Zabel wrote: > >>>>> Did Srini's explanations convinced you? > >>>>> > >>>>> If so, could you queue the series for v3.15? > >>> to be honest, I'm not comfortable with this explanation. If the > >>> "powerdown" bits only gate the clocks to those modules, calling it a > >>> reset control is clearly the wrong abstraction. If that is the case, > >>> couldn't you handle those bits via the clock framework? > >> I just had a re-look at the IPs specs for more information on where > >> these power-down signals are actually terminating on the IP side. > >> > >> For example: ST-Synopsis Ethernet GMAC IP has two pins > >> power_down_req[IN] and power_down_ack[OUT]. power_down_req is used by > >> the software to either put the IP in powerdown or bring it out of > >> powerdown state. > > > > Now I'm a bit confused. There is no mention of GMAC in your patches, > > and for ETH[01] they contain only the SOFTRESET bits. I have no issue > > with the SOFTRESETs. > Yes, GMAC was a bad example indeed. However this same logic applies to > the USB IP as well. > > GMAC power-down-reset can be added to the power-down-reset list for > consistency. > > We did not define the power-down-reset for GMAC because the reset state > of GMAC will not be in power down. softreset should be enough to bring > the IP in to a usable state. So the software never drives the power > down-request but instead uses softreset in this particular case. > > > > >> The IP itself drives power_down_ack to indicate when the power down > >> request is successfully finished. For power_down/power_up request the IP > >> will change the internal state accordingly including powering up/down > >> its internal blocks and/or clock gating. > >> > >>> If on the other hand these powerdown bits also trigger reset machinery, > >>> such that asserting and deasserting that bit will change the module's > >>> internal state, I could be convinced to queue them like this. > >> This is true with ST IPs, these lines change the state of the IP as > >> described above. Reset framework seems to fits in very well with this > >> behavior rather than power-domains or clock framework. > > > > If you put the IP in power down when it is idle, and then power it up > > again, will the IP registers have kept their previous state? > No, the context is lost, the IP needs re-initialization. alright then, I'll add them to the queue. thanks Philipp -- 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/