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 A5FF1C6FD18 for ; Wed, 19 Apr 2023 08:14:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231308AbjDSIOG (ORCPT ); Wed, 19 Apr 2023 04:14:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55508 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232302AbjDSIOG (ORCPT ); Wed, 19 Apr 2023 04:14:06 -0400 Received: from mail-ej1-x62f.google.com (mail-ej1-x62f.google.com [IPv6:2a00:1450:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 766C9138 for ; Wed, 19 Apr 2023 01:14:04 -0700 (PDT) Received: by mail-ej1-x62f.google.com with SMTP id xd13so45542364ejb.4 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=BcQTIek8dCORL0FqfM8PUTuPSjKC897ZZcQa52rAiwjSml4QmfjmVgg1hsHlUyRjql 6XBIi+Cb1v/GaTaSjELFsdAlZOKtmkInCgLbnYRVZR7darqDmnjWigGUAQi5STNd7pde dwpc1jobJ3KgBa50c80bx8/awaAlxa4esdHMh4FtuwEPfCvDNNt4Grby6uk4mhHhwnJ1 X+b3chHvRNp4s8zCXig1Z5W3O5z3VbdokeGW6ldPLV1Mm3q8TT0aFL8EVUQFa/rowZRi j8tvKhDJIrRgLqGdcJqkKQw9tqNMcwnu2VeSzcKxUht0YKoHr/oZAPCf2Jf7i6nBM3ym Ip0g== X-Gm-Message-State: AAQBX9eI6qbrmZj2qHis4Oneh+kk6xOLixAUCMHZmjb/CP83UBE03sk5 IkPU6ZU93s0j9qgm+mE1krFiLg== 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> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.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