Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965159AbaKNOhB (ORCPT ); Fri, 14 Nov 2014 09:37:01 -0500 Received: from mail-ob0-f169.google.com ([209.85.214.169]:47465 "EHLO mail-ob0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934535AbaKNOg7 convert rfc822-to-8bit (ORCPT ); Fri, 14 Nov 2014 09:36:59 -0500 MIME-Version: 1.0 In-Reply-To: <20141113235840.GS26481@atomide.com> References: <1415051968-4878-1-git-send-email-marek@goldelico.com> <1415051968-4878-5-git-send-email-marek@goldelico.com> <5463585D.9070209@ti.com> <20141112150210.GC26481@atomide.com> <5464969F.30708@ti.com> <20141113182848.GQ26481@atomide.com> <20141113235840.GS26481@atomide.com> Date: Fri, 14 Nov 2014 16:36:58 +0200 Message-ID: Subject: Re: [PATCH 4/4] arm: dts: omap3-gta04: Add static configuration for devconf1 register From: Grazvydas Ignotas To: Tony Lindgren Cc: Paul Walmsley , Mark Rutland , devicetree@vger.kernel.org, "linux-fbdev@vger.kernel.org" , Russell King - ARM Linux , pawel.moll@arm.com, ijc+devicetree@hellion.org.uk, "Dr. H. Nikolaus Schaller" , "linux-kernel@vger.kernel.org" , robh+dt@kernel.org, Tero Kristo , Tomi Valkeinen , bcousson@baylibre.com, galak@codeaurora.org, Grant Likely , Marek Belisko , "linux-omap@vger.kernel.org" , Jean-Christophe PLAGNIOL-VILLARD , "linux-arm-kernel@lists.infradead.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 14, 2014 at 1:58 AM, Tony Lindgren wrote: > * Paul Walmsley [141113 15:01]: >> Hi >> >> On Thu, 13 Nov 2014, Tony Lindgren wrote: >> >> > * Tomi Valkeinen [141113 03:33]: >> > > On 12/11/14 17:02, Tony Lindgren wrote: >> > > >> > > >> And, with a quick grep, I see CONTROL_DEVCONF1 touched in multiple >> > > >> places in the kernel. I wonder if adding a pinmux entry for it could >> > > >> cause some rather odd problems. >> > > > >> > > > They can all use pinctrl-single no problem. >> > > >> > > Can, but don't. That's my worry. If we touch the DEVCONF1 via pinmux, >> > > and we have code in mach-omap2 that also touch DEVCONF1, without any >> > > knowledge (and locking) between those... >> > >> > Hmm yeah the McBSP clock mux could be racy as the mux register for >> > McBSP is treated as a clock. This register muxes the clock between >> > external pin and internal clock. Considering that this should be >> > selectable at board level as the external clock probably needs to be >> > used if level shifters are being used, it should be really handled by >> > pinctrl-single. >> > >> > The other use for hsmmc.c and pdata-quirks.c for the one time mux for >> > MMC clock from the MMC clock pin. That can be done with pinctrl-single >> > from the MMC driver too for DT based booting. >> > >> > Then we just have the save and restore of the registers for >> > off-idle. >> > >> > > So _maybe_ that's not an issue, as the pinmux config we have here is >> > > fixed, and done once at boot time, and maybe the code in mach-omap2 that >> > > touch DEVCONF1 is also ran just once and not at the same time as the >> > > pinmux. But I don't know if that's so. >> > >> > It seems we could just do a read-only check for McBSP in the clock >> > code for the mux register, or even completely drop that code from >> > cclock3xxx_data.c and start using the pinctrl for that mux. >> > >> > Paul & Tero, got any comments here? >> >> It's best to move all of the SCM register reads/writes to an SCM IP block >> driver. This driver would be the only entity that would touch the SCM IP >> block registers - no other code on the system would touch it (perhaps >> aside from anything needed for early init). The SCM driver would enforce >> mutual exclusion via a spinlock, so concurrent SCM register modifications >> wouldn't flake out. Then the SCM driver would register clocks with the >> CCF, register pins with the pinctrl subsystem, etc. etc. > > We actually do have that with pinctrl-single + syscon. We certainly > need to implement more Linux framework drivers for the SCM registers. > Things like regulators, clocks, and PHYs, but they should use > pinctrl-single + syscon. See the the pbias-regulator.c for example. > > Looking at the McBSP clock handling, threre's yet more handling of > the same DEVCONF1 mux register in omap2_mcbsp_set_clks_src that gets > alled from omap_mcbsp_dai_set_dai_sysclk. > > To me it seems that if we handle the DEVCONF with pinctrl-single, we > don't need most of the McBSP fck code or the omap2_mcbsp_set_clks_src. > Having the mux register as the clock enable register is not nice.. > Who knows what the clock coming from the external pin might be :) How will audio do dynamic muxing without that code? The pin must be remuxed back to internal clock when audio stops, or else PM breaks. GraÅžvydas -- 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/