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 5A164C636D3 for ; Mon, 30 Jan 2023 18:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236242AbjA3SiV (ORCPT ); Mon, 30 Jan 2023 13:38:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237410AbjA3SiB (ORCPT ); Mon, 30 Jan 2023 13:38:01 -0500 Received: from mail-oa1-f42.google.com (mail-oa1-f42.google.com [209.85.160.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 71E26170F; Mon, 30 Jan 2023 10:37:08 -0800 (PST) Received: by mail-oa1-f42.google.com with SMTP id 586e51a60fabf-15085b8a2f7so16264747fac.2; Mon, 30 Jan 2023 10:37:08 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=QYdypphiGiORHl5j+yMljNsD206DEi5H26RsKdcAI+U=; b=Qcsfcuw3JsZ3s+ul+flK+YNEKgIisO4V3wKaxtz2zvdgh7zjLMKGVfFxUxqGaKunX1 +Z3jvrLd1z+KXPQ0VsDdN6CS1ljv9ui3pqEHYywQ3jLtXpQKnKhkSPCRKuFPLTgjrjmf rCgC+XUH9OhNcC4Ij65SRREKJrVp17A7k4IfaPGj1dT1I9KLGLFyE9NVFcyYmh40p6mW RPvPxJ7dlLTvuTsvbYb/cubD9U6ZGSJgD0ZZPvLqhPaav2JmebpnAjkX8EZtPigt9d0o BKvDq5AhW9La9/gw0DVpHEoEJSkjU2f/cJPi40ZJJpRcz9clIB7tGjOX35Ibvdo2SuDQ rUAw== X-Gm-Message-State: AO0yUKWlJu5wikZQ/eN+SyXvvxFBjPcNnsdImm6qD5WYyfywR5F8YbvK ENj1UJi3JlOCRI5fB1S9Lpsk38j9mg== X-Google-Smtp-Source: AK7set/Idt/xWQrTCTneEaD3YHNIFguFuZSIGGEp1x4r/NuMnynSUl3elQgOA/OFI4IM6OQ2n1CcmA== X-Received: by 2002:a05:6870:ac1e:b0:163:28c9:beef with SMTP id kw30-20020a056870ac1e00b0016328c9beefmr11845994oab.59.1675103827642; Mon, 30 Jan 2023 10:37:07 -0800 (PST) Received: from robh_at_kernel.org (66-90-144-107.dyn.grandenetworks.net. [66.90.144.107]) by smtp.gmail.com with ESMTPSA id c11-20020a544e8b000000b0037854b52db4sm1270294oiy.55.2023.01.30.10.37.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Jan 2023 10:37:07 -0800 (PST) Received: (nullmailer pid 3088245 invoked by uid 1000); Mon, 30 Jan 2023 18:37:06 -0000 Date: Mon, 30 Jan 2023 12:37:06 -0600 From: Rob Herring To: "Leonard, Niall" Cc: Krzysztof Kozlowski , Linus Walleij , Bartosz Golaszewski , Krzysztof Kozlowski , "linux-gpio@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio bindings Message-ID: <20230130183706.GA3079628-robh@kernel.org> References: <20230126-gpio-mmio-fix-v1-0-8a20ce0e8275@ncr.com> <20230126-gpio-mmio-fix-v1-1-8a20ce0e8275@ncr.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Mon, Jan 30, 2023 at 01:20:55PM +0000, Leonard, Niall wrote: > On 29/01/2023 15:59, Krzysztof Kozlowski wrote: > > *External Message* - Use caution before opening links or attachments > > > > On 27/01/2023 12:39, Leonard, Niall wrote: > >> > >> > >>> -----Original Message----- > >>> From: Krzysztof Kozlowski > >>> Sent: 26 January 2023 12:29 > >>> To: Leonard, Niall ; Linus Walleij > >>> ; Bartosz Golaszewski ; Rob > >>> Herring ; Krzysztof Kozlowski > >>> > >>> Cc: linux-gpio@vger.kernel.org; devicetree@vger.kernel.org; linux- > >>> kernel@vger.kernel.org > >>> Subject: Re: [PATCH 1/3] gpio: dt-bindings: add new property to wd,mbl-gpio > >>> bindings > >>> > >>> *External Message* - Use caution before opening links or attachments > >>> > >>> On 26/01/2023 11:17, Niall Leonard via B4 Submission Endpoint wrote: > >>>> From: Niall Leonard > >>> > >>> Subject: missing "wd,mbl-gpio:" prefix. > >>> > >>> Subject: drop second/last, redundant "bindings". The "dt-bindings" > >>> prefix is already stating that these are bindings. > >>> > >>>> > >>>> Added optional "no-input" property > >>> > >>> Missing full stop. > >>> > >>>> > >>>> Signed-off-by: Niall Leonard > >>>> --- > >>>> Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt | 1 + > >>>> 1 file changed, 1 insertion(+) > >>>> > >>>> diff --git a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> index 038c3a6a1f4d..9405f9dad522 100644 > >>>> --- a/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> +++ b/Documentation/devicetree/bindings/gpio/wd,mbl-gpio.txt > >>>> @@ -18,6 +18,7 @@ Required properties: > >>>> > >>>> Optional properties: > >>>> - no-output: GPIOs are read-only. > >>>> + - no-input: GPIOs are write-only. Read is via a shadow register. > >>> > >>> Why this property is needed? Why driver cannot always use shadow > >>> register? > >>> > >> The shadow register is currently only used during the write operation. It is not available during the read operation. > > > > You just wrote above that reading is via shadow register, so how can it > > not be available for reads? Again, why you cannot always read via shadow > > register and need to make a property? You mean that for other GPIOs > > there is no shadow register at all? > > > The existing read method does not use the shadow register. > > static int bgpio_get(struct gpio_chip *gc, unsigned int gpio) > { > return !!(gc->read_reg(gc->reg_dat) & bgpio_line2mask(gc, gpio)); > } > > > What changes between one board and another that justifies this property? > > I have a couple of boards where the electronics engineer decided to only > use the chip select line, so no read/write signal is connected. This > means that reading the address activates the chip select and drives the > contents of the data bus to the port. This part makes sense as you explained the h/w. > For example is someone reads the > file /sys/kernel/debug/gpio this corrupts the port. So I have had to add > this property to avoid that situation. Not quite relevant to the DT binding being a Linux detail. > > If you are strongly against this then just reject it and I will look > after it myself. I thought there may be others who would find this > change useful. A property for a board level quirk is appropriate. You just need to explain that in the commit message rather than stating what the diff already tells us. Rob