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 3F212C433EF for ; Thu, 13 Jan 2022 09:08:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233008AbiAMJIP (ORCPT ); Thu, 13 Jan 2022 04:08:15 -0500 Received: from mail-ed1-f47.google.com ([209.85.208.47]:43643 "EHLO mail-ed1-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232404AbiAMJIO (ORCPT ); Thu, 13 Jan 2022 04:08:14 -0500 Received: by mail-ed1-f47.google.com with SMTP id m4so20460216edb.10; Thu, 13 Jan 2022 01:08:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=wC2KgNOyavftb+JH6q0bbSSTyPPUp1FHUEoqTU+2oII=; b=SOnD2sGfqZsRZXBYWXVODzMnFQBlc4FE4Hi5xuglrYlrAadZlzgCX6k/kkBP1zAOM2 gKoUEs7xA2EiPxI912UDla9wOJOE6NzyHVRXoTIs7Bu6vwnFz/Xp2At4WeXLDA3nGMEv 7UUzfX19eKfMMf1gbFPOzoVC0hzNoFoGPNz2A/qyLCcJhFX864BcNJonImNCPRRCCYdF qiy+FCCB+Fe1uKeUBxf1YYJH+S1b6vuiixcPFHQEa/8UK62zckClf3PpUg+fSx1QCeWO fjSf+F4yl4eQQHVwBLMGkavF8zmendCk8krhUqddO/YnNdQtVIXVUV8KhFwOUD8Aalhy 9ffA== X-Gm-Message-State: AOAM5329hbOFW6d+UrKbMlWMOTfdlwsJvDhXLxz2ebMHFDGSq/tx/we5 sO1ZCpAMLR2skfNoXgM0Oaw= X-Google-Smtp-Source: ABdhPJxDvbw8uDi/CZCHdNVb8ZF0cm/dXO5wxlQuyJkPUYQmVI9ihlrf7qz1xLinH94LB5ZX9C933w== X-Received: by 2002:a05:6402:6cf:: with SMTP id n15mr3235992edy.353.1642064893088; Thu, 13 Jan 2022 01:08:13 -0800 (PST) Received: from [192.168.1.49] (185-219-167-24-static.vivo.cz. [185.219.167.24]) by smtp.gmail.com with ESMTPSA id 20sm656699ejy.105.2022.01.13.01.08.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Jan 2022 01:08:12 -0800 (PST) Message-ID: Date: Thu, 13 Jan 2022 10:08:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Subject: Re: [PATCH v6 2/2] serial:sunplus-uart:Add Sunplus SoC UART Driver Content-Language: en-US To: hammer hsieh Cc: Greg KH , robh+dt@kernel.org, linux-serial@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, p.zabel@pengutronix.de, wells.lu@sunplus.com, "hammer.hsieh" References: <1641979444-11661-1-git-send-email-hammerh0314@gmail.com> <1641979444-11661-3-git-send-email-hammerh0314@gmail.com> From: Jiri Slaby In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 13. 01. 22, 9:54, hammer hsieh wrote: >>> +static void sunplus_shutdown(struct uart_port *port) >>> +{ >>> + unsigned long flags; >>> + >>> + spin_lock_irqsave(&port->lock, flags); >>> + writel(0, port->membase + SUP_UART_ISC); >>> + spin_unlock_irqrestore(&port->lock, flags); >> >> I asked last time: >> * What bus is this -- posting? >> >> You replied: >> * Here just clear interrupt. >> * Not really understand your comment? >> >> So I am asking again: >> What bus is this? Isn't a posted write a problem here? I mean, shouldn't >> you read from the register so that the write hits the device? That >> depends on the bus this sits on, so just asking. >> > > Each UART has its own ISC register. > Ex. > dev/ttySUP0 base_adr = 0x9C00-0000 , isc_addr = 0x9C00-001C > dev/ttySUP1 base_adr = 0x9C00-0080 , isc_addr = 0x9C00-009C > dev/ttySUP2 base_adr = 0x9C00-0100 , isc_addr = 0x9C00-011C > dev/ttySUP3 base_adr = 0x9C00-0180 , isc_addr = 0x9C00-019C > dev/ttySUP4 base_adr = 0x9C00-0200 , isc_addr = 0x9C00-021C > So sunplus_shutdown() just simply turn off its own device isc only. > That's why I didn't read register value, just write 0 for it. Could you explain me what posted write is and how does it not matter in this case? thanks, -- js suse labs