From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 747A6C433E0 for ; Wed, 20 May 2020 17:42:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E1C6207D3 for ; Wed, 20 May 2020 17:42:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726439AbgETRmX (ORCPT ); Wed, 20 May 2020 13:42:23 -0400 Received: from mail-oi1-f196.google.com ([209.85.167.196]:35674 "EHLO mail-oi1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726821AbgETRmV (ORCPT ); Wed, 20 May 2020 13:42:21 -0400 Received: by mail-oi1-f196.google.com with SMTP id o7so3712012oif.2 for ; Wed, 20 May 2020 10:42:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=MD7c5pfPj07V6w+/1HikBFi1jG/xPnFg9bdLzM6lBI0=; b=XXoYOJ8Es55dGY+33rdKxD0zMH4BSSViPi3kXfwDgHl8wt3twGsFCcHewqcMhWGLp7 IwmCNvVSkA8Wt58uwX5Ya2iKbVimMQx3A6Sf4TlglwTQHyYfBeny7DatcmQm1LVNuH1S oIYkYGIUgTTE2ItCK+GRSlCYU6ps5kDIkW9oxmRhJg/j/5Ej5zyFlqzUlXC6CyIDMguN I0OuQOGOjBcvEqqA594jFvelikrHGilX4fPhpl25vMcTBuuiTBvLY2tclL3/rk67WQKa 17/1X/wJrzHV7dDle6RAOwb098K+Mx+1b7j2gq2bDRH7Hkzs5HattlJKTTY0n58B6TCl GAWQ== X-Gm-Message-State: AOAM533C3jnnymFVArNSzy0BMxyKOzt//gxjKONSy/2tJO1oL65eagPj 2RsJN7dYXXLDQcXJxIXrVONgxf6KRJgIivaysmA= X-Google-Smtp-Source: ABdhPJyyZ+hC+IxFdxiETDXrpe1e0y9Y8vZK1BlLd7FtFwaEAhdt8xJr+jIBJgk+v/5JzYYnHUcU/ALuyV4DtEvlPBo= X-Received: by 2002:aca:210a:: with SMTP id 10mr2502041oiz.153.1589996539784; Wed, 20 May 2020 10:42:19 -0700 (PDT) MIME-Version: 1.0 References: <20200519152445.6922-1-ulf.hansson@linaro.org> In-Reply-To: From: Geert Uytterhoeven Date: Wed, 20 May 2020 19:42:08 +0200 Message-ID: Subject: Re: [PATCH 2/2] mmc: tmio: Make sure the PM domain is 'started' while probing To: Ulf Hansson Cc: Linux MMC List , Masahiro Yamada , Wolfram Sang , Ulrich Hecht , Simon Horman , Niklas Soderlund Content-Type: text/plain; charset="UTF-8" Sender: linux-mmc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-mmc@vger.kernel.org Hi Ulf, On Wed, May 20, 2020 at 6:12 PM Ulf Hansson wrote: > On Wed, 20 May 2020 at 17:57, Geert Uytterhoeven wrote: > > On Tue, May 19, 2020 at 5:24 PM Ulf Hansson wrote: > > > If the tmio device is attached to a genpd (PM domain), that genpd may have > > > ->start|stop() callback assigned to it. To make sure the device is > > > accessible during ->probe(), genpd's ->start() callback must be invoked, > > > which is currently managed by tmio_mmc_host_probe(). However, it's likely > > > that may be too late for some cases, as registers may be read and written > > > way before that point. > > > > > > To fix the behaviour, let's move the call to dev_pm_domain_start() from > > > tmio_mmc_host_probe() into those clients that needs it. From discussions at > > > linux-mmc mailing list, it turned out that it should be sufficient to do > > > this for the SDHI renesas variants, hence the call is move to > > > renesas_sdhi_probe(). > > > > > > Signed-off-by: Ulf Hansson > > > --- > > > drivers/mmc/host/renesas_sdhi_core.c | 3 +++ > > > drivers/mmc/host/tmio_mmc_core.c | 2 -- > > > 2 files changed, 3 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/mmc/host/renesas_sdhi_core.c b/drivers/mmc/host/renesas_sdhi_core.c > > > index ff72b381a6b3..dcba9ad35dd1 100644 > > > --- a/drivers/mmc/host/renesas_sdhi_core.c > > > +++ b/drivers/mmc/host/renesas_sdhi_core.c > > > @@ -24,6 +24,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > #include > > > #include > > > #include > > > @@ -905,6 +906,8 @@ int renesas_sdhi_probe(struct platform_device *pdev, > > > /* All SDHI have SDIO status bits which must be 1 */ > > > mmc_data->flags |= TMIO_MMC_SDIO_STATUS_SETBITS; > > > > > > + dev_pm_domain_start(&pdev->dev); > > > + > > > > > > I have debug prints at the top of genpd_stop_dev(): > > > > pr_info("==== %s/%s: stop\n", genpd->name, dev_name(dev)); > > > > and genpd_start_dev(): > > > > pr_info("==== %s/%s: start\n", genpd->name, dev_name(dev)); > > > > On Koelsch (R-Car M2-W), the three SDHI devices are started twice: > > > > PM: ==== always-on/ee100000.sd: start > > PM: ==== always-on/ee140000.sd: start > > PM: ==== always-on/ee160000.sd: start > > PM: ==== always-on/ee100000.sd: start > > PM: ==== always-on/ee140000.sd: start > > PM: ==== always-on/ee160000.sd: start > > > > The first time, the probe is deferred, because the regulator needed in > > tmio_mmc_init_ocr() hasn't been instantiated yet. The SDHI device is > > detached from the PM domain, but not stopped. > > Interestingly, I see no clock imbalances afterwards. > > That's because genpd's->detach_dev() callback is invoked at the > "deferred probe" case. In your case this ends up calling > pm_clk_destroy(). Thus the clock gets disabled and unprepared > correctly. Indeed, I had just arrived at the same conclusion. While genpd doesn't have reference counting on start/stop, pm_clk does have pce_status to track state, so when needed, __pm_clk_remove() disables the clock before its destruction. > > On R-Car Gen3, R-Mobile A1, and RZ/A systems, they are started once, > > as expected. > > > > On R-Mobile APE6 and SH-Mobile AG5, one device is stopped and started > > again: > > > > PM: ==== a3sp/ee100000.sd: start > > PM: ==== a3sp/ee120000.sd: start > > PM: ==== a3sp/ee120000.sd: stop > > PM: ==== a3sp/ee120000.sd: start > > > > But here no probe deferral is involved. > > Just Runtime PM kicking in, I guess. > > Yep, and that's okay, right? Correct. > > > @@ -1192,7 +1191,6 @@ int tmio_mmc_host_probe(struct tmio_mmc_host *_host) > > > /* See if we also get DMA */ > > > tmio_mmc_request_dma(_host, pdata); > > > > > > - dev_pm_domain_start(&pdev->dev); > > > > Before, the issue on probe deferral didn't happen, as the device was only > > started after the regulator was found. > > I am not sure there is an issue or did I miss something? No, it's just a bit strange to see an imbalance in start/stop. Note that this does mean that all PM domain providers that do not rely on pm_clk, but have their own start/stop methods, need to be aware of this quirk, and should take care of reference counting themselves. Fortunately there seems to be only one: drivers/soc/ti/ti_sci_pm_domains.c. Unfortunately it doesn't do reference counting, so if that PM domain driver is ever used with a driver that calls dev_pm_domain_start(), mysterious things may happen... > Thanks a lot for testing and sharing results! Very much appreciated! So I guess I can provide my Tested-by: Geert Uytterhoeven for this one, too, finally. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds