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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83BD3CDB474 for ; Fri, 20 Oct 2023 16:43:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1377907AbjJTQnS (ORCPT ); Fri, 20 Oct 2023 12:43:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55148 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229775AbjJTQnQ (ORCPT ); Fri, 20 Oct 2023 12:43:16 -0400 Received: from fllv0015.ext.ti.com (fllv0015.ext.ti.com [198.47.19.141]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A32418F; Fri, 20 Oct 2023 09:43:14 -0700 (PDT) Received: from fllv0035.itg.ti.com ([10.64.41.0]) by fllv0015.ext.ti.com (8.15.2/8.15.2) with ESMTP id 39KGh4dA110130; Fri, 20 Oct 2023 11:43:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1697820184; bh=LLn14VYW09aZCrIvFtLla5eOZlSgOm259OWBlpoCGrU=; h=Date:Subject:To:CC:References:From:In-Reply-To; b=ciK1JwYPKdOP/Dt0WZ9BwjUGkdJgibACQINlVdmpSWncpg4Jk+/tJwlcIX9eN4hgu aOlf8ZnATWq0cOQajrthIo6rEjMmX09h84fEH4GZf0x3Bzi5QWenTOoTo342cVxIaw tvUKO7nT8XqVdJWz+5zm6ElW4Z7BpeioyJg7AAIg= Received: from DFLE105.ent.ti.com (dfle105.ent.ti.com [10.64.6.26]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 39KGh4lZ039416 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 20 Oct 2023 11:43:04 -0500 Received: from DFLE102.ent.ti.com (10.64.6.23) by DFLE105.ent.ti.com (10.64.6.26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23; Fri, 20 Oct 2023 11:43:04 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DFLE102.ent.ti.com (10.64.6.23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2507.23 via Frontend Transport; Fri, 20 Oct 2023 11:43:04 -0500 Received: from [128.247.81.1] (ileaxei01-snat2.itg.ti.com [10.180.69.6]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 39KGh4RB042120; Fri, 20 Oct 2023 11:43:04 -0500 Message-ID: Date: Fri, 20 Oct 2023 11:43:04 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mux: mmio: use reg property when parent device is not a syscon Content-Language: en-US To: Peter Rosin , Greg Kroah-Hartman , Rob Herring , Krzysztof Kozlowski , Nishanth Menon , Vignesh Raghavendra CC: , References: <20230911151030.71100-1-afd@ti.com> <0cb645c7-f3c5-e4bb-7686-2a83d32274bb@axentia.se> From: Andrew Davis In-Reply-To: <0cb645c7-f3c5-e4bb-7686-2a83d32274bb@axentia.se> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/20/23 9:28 AM, Peter Rosin wrote: > Hi! > > 2023-09-11 at 17:10, Andrew Davis wrote: >> The DT binding for the reg-mux compatible states it can be used when the >> "parent device of mux controller is not syscon device". It also allows >> for a reg property. When the reg property is provided, use that to >> identify the address space for this mux. If not provided fallback to >> using the parent device as a regmap provider. >> >> Signed-off-by: Andrew Davis >> Reviewed-by: Nishanth Menon >> --- >> >> Changes from v2: >> - Rebased on v6.6-rc1 >> >> Changes from v1: >> - Flip logic as suggested in v1[0] >> >> [0] https://lore.kernel.org/lkml/1c27d9d4-b1cc-c158-90f7-f7e47e02c424@ti.com/T/ >> >> drivers/mux/mmio.c | 9 ++++++--- >> 1 file changed, 6 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/mux/mmio.c b/drivers/mux/mmio.c >> index fd1d121a584ba..b6095b7853ed2 100644 >> --- a/drivers/mux/mmio.c >> +++ b/drivers/mux/mmio.c >> @@ -44,10 +44,13 @@ static int mux_mmio_probe(struct platform_device *pdev) >> int ret; >> int i; >> >> - if (of_device_is_compatible(np, "mmio-mux")) >> + if (of_device_is_compatible(np, "mmio-mux")) { >> regmap = syscon_node_to_regmap(np->parent); >> - else >> - regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV); >> + } else { >> + regmap = device_node_to_regmap(np); > > I started digging in device_node_to_regmap() to try to find an error that > could be used to trigger if the failover to dev_get_regmap() should be > tried, instead of always doing the failover on error. I got lost fairly > quickly, but it seems device_node_to_regmap() can return -EDEFER_PROBE. > While I'm not certain that it is applicable, that case should probably > not fall back to dev_get_regmap()... > > Are there other error cases that should prevent the failover? I would > guess that it's perhaps just a single error that should trigger trying > the failover path? But I don't know, and which error if that's the case? > Ideally the only error that will be returned is ENOMEM, which happens when this node does not have a 'reg' property, and this is also the one case we want to do the failover. So all should be well. > How much badness can be caused if syscon_node_to_regmap() fails for some > random obscure reason and the failover path is taken inadvertently? It > certainly smells bad for -EDEFER_PROBE, but do you have any insight in > other cases? > If we take the failover inadvertently then we will check if the parent node is a syscon, if it is then our offset will most likely be wrong (parent will not match child 'reg'). > And after getting to approx that point a while back, I had other things > to take care of, and this fell off the table. Sorry! > No problem as long as we can find a way to get this in quickly (lot of DT warning need cleaned up based on this patch). Thanks Andrew > Cheers, > Peter > >> + if (IS_ERR(regmap)) >> + regmap = dev_get_regmap(dev->parent, NULL) ?: ERR_PTR(-ENODEV); >> + } >> if (IS_ERR(regmap)) { >> ret = PTR_ERR(regmap); >> dev_err(dev, "failed to get regmap: %d\n", ret);