From patchwork Tue Jun 16 00:09:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Robin Murphy X-Patchwork-Id: 11606051 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C176090 for ; Tue, 16 Jun 2020 00:10:41 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 9BC9020739 for ; Tue, 16 Jun 2020 00:10:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Xer3+aYF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BC9020739 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=CknNmrcA0We6xzmc2vPJ4oXIFBX/WQfyeLSSRDkZVy4=; b=Xer3+aYFRMlB1v Qt2lCEGgPZBQbCQN/QdVmqsQldf48pCIhg1AamIj3X/uDVnwoqzPdqcFUpyhpBJcRQZuYSG1CPbyl O2n4ZKIG0I10Idjhbq+ykKYJ1L5ekJAfWIn//reK+BiphJ3/q1KjuhrWXRSblvSiBJUN2E2RdiaJx YhRXqEke9TYMmKPRuApKiMCYbyUBruWph3UrhS0gA/nS/QuESt3TikKF6FFN2XiTDMojFe40biZjM JVH54EXMZEXtvmX9puYC41fpItn7Ykm47CX+9CSrTziy5h6R/C6PvLFwXnNDJDYCTUra00j/XWEt+ GMSyafxSi/lTYPqMlhQg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jkzBP-0003PN-G5; Tue, 16 Jun 2020 00:10:31 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jkzAe-0000Iu-6M; Tue, 16 Jun 2020 00:09:45 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CD7FC1045; Mon, 15 Jun 2020 17:09:43 -0700 (PDT) Received: from e121345-lin.cambridge.arm.com (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 447363F73C; Mon, 15 Jun 2020 17:09:42 -0700 (PDT) From: Robin Murphy To: broonie@kernel.org, nsaenzjulienne@suse.de, f.fainelli@gmail.com, rjui@broadcom.com, sbranden@broadcom.com Subject: [PATCH 3/3] spi: bcm2835: Micro-optimise FIFO loops Date: Tue, 16 Jun 2020 01:09:29 +0100 Message-Id: <9242863077acf9a64e4b3720e479855b88d19e82.1592261248.git.robin.murphy@arm.com> X-Mailer: git-send-email 2.23.0.dirty In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200615_170944_298514_F2BD6456 X-CRM114-Status: GOOD ( 12.16 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at https://www.dnswl.org/, medium trust [217.140.110.172 listed in list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, lukas@wunner.de, bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, kernel@martin.sperl.org, linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org The blind and counted loops are always called with nonzero count, so convert them to do-while loops that lead to slightly more efficient code generation. With GCC 8.3 this shaves off 1-2 instructions per iteration in each case. Signed-off-by: Robin Murphy --- drivers/spi/spi-bcm2835.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-) diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index aec70ac8911e..e9a91adf03eb 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -245,13 +245,13 @@ static inline void bcm2835_rd_fifo_count(struct bcm2835_spi *bs, int count) bs->rx_len -= count; - while (count > 0) { + do { val = bcm2835_rd(bs, BCM2835_SPI_FIFO); len = min(count, 4); memcpy(bs->rx_buf, &val, len); bs->rx_buf += len; count -= 4; - } + } while (count > 0); } /** @@ -271,7 +271,7 @@ static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count) bs->tx_len -= count; - while (count > 0) { + do { if (bs->tx_buf) { len = min(count, 4); memcpy(&val, bs->tx_buf, len); @@ -281,7 +281,7 @@ static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count) } bcm2835_wr(bs, BCM2835_SPI_FIFO, val); count -= 4; - } + } while (count > 0); } /** @@ -310,12 +310,11 @@ static inline void bcm2835_rd_fifo_blind(struct bcm2835_spi *bs, int count) count = min(count, bs->rx_len); bs->rx_len -= count; - while (count) { + do { val = bcm2835_rd(bs, BCM2835_SPI_FIFO); if (bs->rx_buf) *bs->rx_buf++ = val; - count--; - } + } while (--count); } /** @@ -330,11 +329,10 @@ static inline void bcm2835_wr_fifo_blind(struct bcm2835_spi *bs, int count) count = min(count, bs->tx_len); bs->tx_len -= count; - while (count) { + do { val = bs->tx_buf ? *bs->tx_buf++ : 0; bcm2835_wr(bs, BCM2835_SPI_FIFO, val); - count--; - } + } while (--count); } static void bcm2835_spi_reset_hw(struct bcm2835_spi *bs)