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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DA7A5C77B73 for ; Wed, 19 Apr 2023 08:15:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wHg5Or2DMGI8ZtHbM8ZxsSVIJyrJ/3fFbR+kpAhLIKI=; b=jM+jqVF3ldRPF6 5OyPSELpjOZdHIRSqB8OZxz4phpRtk6QxI1sIgGOH4H468/ISOe4uTIMiZaYxex8W80ibrrrP8RYG S6NV19a1C+0a40GwNKqzCnKu/3Wpr9RRs4houiYXnoOFwjJ7hvQ0uQOGHd8aIeV8lqDLUH40IDz1g OEE6svoY3s4L/p2RQTkzMnsP7o5lZvUfFZOEure9R5Msr1SP88uVXA4QBxTGeGhDm7hxHVauFhp3d g02wMcenwnUMsbnK9zoaTi6hmoI1QNH0I0v5eQ86bWhyMhqJJw1pu0rkIP3rvF0MJ88aRvLW+rzKo 6ZsXL2I+/rtMy3SWMMQQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pp2x8-004YUY-2w; Wed, 19 Apr 2023 08:14:10 +0000 Received: from mail-ej1-x62a.google.com ([2a00:1450:4864:20::62a]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pp2x6-004YSW-0W for linux-arm-kernel@lists.infradead.org; Wed, 19 Apr 2023 08:14:09 +0000 Received: by mail-ej1-x62a.google.com with SMTP id b16so4197202ejz.3 for ; Wed, 19 Apr 2023 01:14:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1681892043; x=1684484043; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=KhQTFUqxL/O6643fDSSoSsETDXYAv4dskz8SOtwED14=; b=qm7L/uI38hNO7K25hIzjljA6TS3z+1GhbX80s9u0+gsCU9gjC1yqzZjjZ6IrI8TLj9 +6tPFvEx4YXyENHA4uSqT1ex09scO3tE9K7gX47/XUxyi2tO3oURSdFmWiU212hAcZWF 6fLNFS9h7QDXY2fGJQGgGEwKMN1ElDy2x/CWZSHP2CeNSUEacMJvBK+6zi18UZuHp2H0 mbC3cuSd7nrdW1hU7zfHf71wq4S9lEdLYYmow8f3R8yBeZKy/3fI2gAXNPDD7UDEBQFf 0Vsg/LPhP8sr3XAhZUraMq8Yek2ee2mF+QiOUxwI2pxvIm6O7psUBSof41456nfrkGul 7cEg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681892043; x=1684484043; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=KhQTFUqxL/O6643fDSSoSsETDXYAv4dskz8SOtwED14=; b=hziEqUJf7UwoMCd78+XeGLTXQvgE1lEHTeVDPy948A+l8QxO+pJWXgu6khY9YHVAEy SxLrR/zzOAsh+ntavHoQ25NDF1ObIBhUQePzvUk1NBge7cF0+vM6VcXlHx2ARoBEHrLG U/3BGzxPFtuHWL40SZ03GBuocXakGOwnNPHOH7grk745XdEHhIm8lyAhU1qHADqajyr1 FLRIZMnUsLXzXywQrmDOVD7tYbsLdqeQ/Sh/Mty1foE/DB5Ly3Feb4rQpwmKGkoFENou DbTLmLuDzJszRa3cD5mCAixQpw5vRtDI/ss0GMYq6reZePH7LvhrXRSzUfwS3qrVym/r DKCg== X-Gm-Message-State: AAQBX9ddddnk4wOtWCK8R1OrctcdZY6D4KEkkSEud3Nng57SBdbuLR+v 8LQo234exHjhr/Y6ouxNbG3goA== X-Google-Smtp-Source: AKy350b9AjsV58l2IRVNhBCH2Z5PcQLEDPMWjJpw05daiSBTBqGXMNL+pH2zgPhEYJ9tmvxyeb/0tw== X-Received: by 2002:a17:906:a408:b0:94f:236b:9e3a with SMTP id l8-20020a170906a40800b0094f236b9e3amr1516618ejz.3.1681892042992; Wed, 19 Apr 2023 01:14:02 -0700 (PDT) Received: from ?IPV6:2a02:810d:15c0:828:62f5:eb43:f726:5fee? ([2a02:810d:15c0:828:62f5:eb43:f726:5fee]) by smtp.gmail.com with ESMTPSA id ss2-20020a170907c00200b0094f4b7e2dc5sm5036143ejc.142.2023.04.19.01.14.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Apr 2023 01:14:02 -0700 (PDT) Message-ID: <36f37a18-0022-0368-bf7c-ebdd724b1558@linaro.org> Date: Wed, 19 Apr 2023 10:14:01 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH v2 2/4] spi: s3c64xx: add cpu_relax in polling loop Content-Language: en-US To: Jaewon Kim , Mark Brown , Andi Shyti , Alim Akhtar Cc: linux-spi@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Chanho Park References: <20230419060639.38853-1-jaewon02.kim@samsung.com> <20230419060639.38853-3-jaewon02.kim@samsung.com> From: Krzysztof Kozlowski In-Reply-To: <20230419060639.38853-3-jaewon02.kim@samsung.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230419_011408_199046_6922D570 X-CRM114-Status: GOOD ( 16.26 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 19/04/2023 08:06, Jaewon Kim wrote: > Adds cpu_relax() to prevent long busy-wait. How cpu_relax prevents long waiting? > There is busy-wait loop to check data transfer completion in polling mode. > > Signed-off-by: Jaewon Kim > --- > drivers/spi/spi-s3c64xx.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/spi/spi-s3c64xx.c b/drivers/spi/spi-s3c64xx.c > index 273aa02322d9..886722fb40ea 100644 > --- a/drivers/spi/spi-s3c64xx.c > +++ b/drivers/spi/spi-s3c64xx.c > @@ -568,6 +568,7 @@ static int s3c64xx_wait_for_pio(struct s3c64xx_spi_driver_data *sdd, > > val = msecs_to_loops(ms); > do { > + cpu_relax(); Shouldn't this be just readl_poll_timeout()? Or the syntax would be too complicated? > status = readl(regs + S3C64XX_SPI_STATUS); > } while (RX_FIFO_LVL(status, sdd) < xfer->len && --val); > Best regards, Krzysztof _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel