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 A8675C433F5 for ; Mon, 2 May 2022 16:55:18 +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:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=Y5toX1PgC+gpWfFwt0rdAehvXqurNUaaSR6zf08T2h8=; b=CQAHdSITNsBGCM LZ4WZNY45o48y/NqcFM4iggRALZzThW6B4xvadQbN7BgasDQ8CSLOWoyr5rwhiPrvncTbsp8hkIjS dabYyyKqXJ6XIlQcRC1VybmMTbe3mZqvpTF+N6vv3D6j6NJLw0hUEuEh4KypWu55bVqfORm4EdHLZ BctQ6ItiL9IJN5ZAQ55gCqNw4HABMFHwNk5wT06NqOarbZD6ozH9Z6OUSM9287IvXbi9eYD3nSCo0 lsuBYDsSBGjqVy6JHF1kFYvlfcfKPSNTcNHC9HvHntRS4baEPqTRmw4acDE/bUhH2hslqCry6Ya/a wE5186D41yop6p2ZmH6A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nlZJR-001qjH-GP; Mon, 02 May 2022 16:54:17 +0000 Received: from metis.ext.pengutronix.de ([2001:67c:670:201:290:27ff:fe1d:cc33]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nlZFD-001oKY-KK for linux-arm-kernel@lists.infradead.org; Mon, 02 May 2022 16:49:59 +0000 Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1nlZFC-0002uL-Ef for linux-arm-kernel@lists.infradead.org; Mon, 02 May 2022 18:49:54 +0200 Received: from dspam.blackshift.org (localhost [127.0.0.1]) by bjornoya.blackshift.org (Postfix) with SMTP id 32347734AD for ; Mon, 2 May 2022 16:49:53 +0000 (UTC) Received: from hardanger.blackshift.org (unknown [172.20.34.65]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by bjornoya.blackshift.org (Postfix) with ESMTPS id BD31F73498; Mon, 2 May 2022 16:49:50 +0000 (UTC) Received: from blackshift.org (localhost [::1]) by hardanger.blackshift.org (OpenSMTPD) with ESMTP id 5f2ca864; Mon, 2 May 2022 16:49:32 +0000 (UTC) From: Marc Kleine-Budde To: inux-spi@vger.kernel.org, Fabio Estevam , Marek Vasut Cc: kernel@pengutronix.de, linux-imx@nxp.com, Mark Brown , linux-arm-kernel@lists.infradead.org, Marc Kleine-Budde Subject: [RFC 9/9] spi: spi-imx: mx51_ecspi_prepare_message(): skip writing MX51_ECSPI_CONFIG register if unchanged Date: Mon, 2 May 2022 18:49:31 +0200 Message-Id: <20220502164931.1956137-10-mkl@pengutronix.de> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220502164931.1956137-1-mkl@pengutronix.de> References: <20220502164931.1956137-1-mkl@pengutronix.de> MIME-Version: 1.0 X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-arm-kernel@lists.infradead.org X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220502_094955_744276_16B20591 X-CRM114-Status: GOOD ( 16.25 ) 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 In mx51_ecspi_prepare_message() the MX51_ECSPI_CONFIG register is setup for the current spi_message. After writing the register, there is a delay to ensure that the changes hit the hardware. This patch checks if the register MX51_ECSPI_CONFIG actually needs to be changed. If the register content is unchanged the function is left early, skipping the write to the hardware and the delay. This leads to a small, but measurable performance increase. For a given workload with small transfers on an imx6 single core the CPU load decreases from 30% to ~27%. Signed-off-by: Marc Kleine-Budde --- drivers/spi/spi-imx.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index 798a5182b849..addfed56f1d4 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -519,6 +519,7 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, u32 min_speed_hz = ~0U; u32 testreg, delay; u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG); + u32 current_cfg = cfg; /* set Master or Slave mode */ if (spi_imx->slave_mode) @@ -576,6 +577,9 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, else cfg &= ~MX51_ECSPI_CONFIG_SSBPOL(spi->chip_select); + if (cfg == current_cfg) + return 0; + writel(cfg, spi_imx->base + MX51_ECSPI_CONFIG); /* -- 2.35.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel