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 X-Spam-Level: X-Spam-Status: No, score=-9.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CF27C4360F for ; Mon, 18 Mar 2019 07:34:37 +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 E289920857 for ; Mon, 18 Mar 2019 07:34:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="AEJneagI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E289920857 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.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=LZzytSWg1g3rUYWj1r/PknejUT7zTawQ/pFWn/MI5RI=; b=AEJneagIx5of0w YnFZ+AdbN/Yj6UoNo3zqwYZcF4Ml8lwdsQi9LN0xqd4swX6ipSj4tgBucGFeaAze9CPU0TdeE7+OJ Gg/Cb7TpYetbTRx/ytACuqckzGLJ8YH6ORoJjQ2M/K4H6OFlUNgRfd4z4Ley/OdfrbH7vBDWJwoV2 BcUVUvFAlfK+E50P+QCAiqdyEr2vf4iN5hcYciUjYmlJ/QOzNcuA98aQwXbwezeHxjdcKLOkYcMaT zy3RLMXVl74sVGGEP8TZKd8sGz3koJ1RwfdYt6vcLWLvSwn2HJaTI4wqaFhfpvRoNrsKATt8XmoyH Bnjl9l2qPoVtMAm4bHUQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h5mn0-00027Y-Q6; Mon, 18 Mar 2019 07:34:30 +0000 Received: from mirror2.csie.ntu.edu.tw ([140.112.30.76] helo=wens.csie.org) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h5mmp-0001wj-2H for linux-arm-kernel@lists.infradead.org; Mon, 18 Mar 2019 07:34:20 +0000 Received: by wens.csie.org (Postfix, from userid 1000) id F3F3C5FD69; Mon, 18 Mar 2019 15:34:11 +0800 (CST) From: Chen-Yu Tsai To: Srinivas Kandagatla , Maxime Ripard Subject: [PATCH 2/6] nvmem: sunxi_sid: Optimize register read-out method Date: Mon, 18 Mar 2019 15:33:50 +0800 Message-Id: <20190318073354.12151-3-wens@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190318073354.12151-1-wens@kernel.org> References: <20190318073354.12151-1-wens@kernel.org> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190318_003419_243873_197E729B X-CRM114-Status: GOOD ( 13.74 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: devicetree@vger.kernel.org, linux-sunxi@googlegroups.com, Chen-Yu Tsai , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Chen-Yu Tsai SID cells are 32-bit aligned, and a multiple of 32 bits in length. The only outlier is the thermal sensor calibration data, which is 16 bits per sensor. However a whole 64 bits is allocated for this purpose, so we could consider it conforming to the rule above. Also, the register read-out method assumes native endian, unlike the direct MMIO method, which assumes big endian. Thus no endian conversion is involved. Under these assumptions, the register read-out method can be slightly optimized. Instead of reading one word then discarding 3 bytes, read the whole word directly into the buffer. However, for reads under 4 bytes or trailing bytes, we still use a scratch buffer to extract the requested bytes. We could go one step further if .word_size was 4, but changing that would affect the sysfs interface's behavior. Signed-off-by: Chen-Yu Tsai --- drivers/nvmem/sunxi_sid.c | 38 ++++++++++++++++++-------------------- 1 file changed, 18 insertions(+), 20 deletions(-) diff --git a/drivers/nvmem/sunxi_sid.c b/drivers/nvmem/sunxi_sid.c index 704c35edf796..15fbfab62595 100644 --- a/drivers/nvmem/sunxi_sid.c +++ b/drivers/nvmem/sunxi_sid.c @@ -115,36 +115,34 @@ static int sun8i_sid_register_readout(const struct sunxi_sid *sid, * to be not reliable at all. * Read by the registers instead. */ -static int sun8i_sid_read_byte_by_reg(const struct sunxi_sid *sid, - const unsigned int offset, - u8 *out) -{ - u32 word; - int ret; - - ret = sun8i_sid_register_readout(sid, offset & ~0x03, &word); - - if (ret) - return ret; - - *out = (word >> ((offset & 0x3) * 8)) & 0xff; - - return 0; -} - static int sun8i_sid_read_by_reg(void *context, unsigned int offset, void *val, size_t bytes) { struct sunxi_sid *sid = context; - u8 *buf = val; + u32 word; int ret; - while (bytes--) { - ret = sun8i_sid_read_byte_by_reg(sid, offset++, buf++); + /* .stride = 4 so offset is guaranteed to be aligned */ + while (bytes >= 4) { + ret = sun8i_sid_register_readout(sid, offset, val); if (ret) return ret; + + val += 4; + offset += 4; + bytes -= 4; } + if (!bytes) + return 0; + + /* Handle any trailing bytes */ + ret = sun8i_sid_register_readout(sid, offset, &word); + if (ret) + return ret; + + memcpy(val, &word, bytes); + return 0; } -- 2.20.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel