From patchwork Fri Jul 21 08:03:07 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: zhangqing X-Patchwork-Id: 9856291 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 1FB73600F5 for ; Fri, 21 Jul 2017 07:59:30 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0A5EE2876B for ; Fri, 21 Jul 2017 07:59:30 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id F35AF28781; Fri, 21 Jul 2017 07:59:29 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,RCVD_IN_DNSWL_NONE autolearn=unavailable version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 0D4AD2876B for ; Fri, 21 Jul 2017 07:59:29 +0000 (UTC) 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:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id: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:In-Reply-To: References:List-Owner; bh=JKbTEs3jLbYO/ctuSSfP31YzTUFfU718Cb9OcxqWn8o=; b=gv+ Sv/LkEZ4J8VyoosD6VgYUpDHOTi7SMrGJv5s1kYWP04njG0RA2JTPrGLuMsOrRMSJ9s4C4zl3qsvy WWBNmEHM4Cf+uysptw9LXOTl/PSr3oGVbm6LimSy9hb3vkKYi+tFD+iwFJaRlSmd34ntHqyEoeIG0 tb3Bo9u00Gzjfeyjv0PK1N0fk07sWkGWqS/SlB/L0aWvIFx6SbT+7KhHbItypCjUcyAA6KYUCMPgM sJvGMrSJaLvjEEYtISyHPYbPEDLvy7oYIdhI6sTWvk33dSu5KEofbi/FXH6LQcw+SePzqtCFfcD1i R2QLSPgNyU26LdCh7xGWxRMIYu0xpyQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1dYSqI-0004yt-Bu; Fri, 21 Jul 2017 07:59:22 +0000 Received: from regular1.263xmail.com ([211.150.99.137]) by bombadil.infradead.org with esmtps (Exim 4.87 #1 (Red Hat Linux)) id 1dYSqE-0004wm-IQ; Fri, 21 Jul 2017 07:59:20 +0000 Received: from zhangqing?rock-chips.com (unknown [192.168.167.192]) by regular1.263xmail.com (Postfix) with ESMTP id 3C37FDBB2; Fri, 21 Jul 2017 15:58:49 +0800 (CST) X-263anti-spam: KSV:0; X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-KSVirus-check: 0 X-ABS-CHECKED: 4 Received: from localhost.localdomain (localhost [127.0.0.1]) by smtp.263.net (Postfix) with ESMTPA id 317E73B0; Fri, 21 Jul 2017 15:58:43 +0800 (CST) X-RL-SENDER: zhangqing@rock-chips.com X-FST-TO: mturquette@baylibre.com X-SENDER-IP: 58.22.7.114 X-LOGIN-NAME: zhangqing@rock-chips.com X-UNIQUE-TAG: <30316b4063b2f747ccec5f7c362840a9> X-ATTACHMENT-NUM: 0 X-SENDER: zhangqing@rock-chips.com X-DNS-TYPE: 0 Received: from localhost.localdomain (unknown [58.22.7.114]) by smtp.263.net (Postfix) whith ESMTP id 10126AMEU5C; Fri, 21 Jul 2017 15:58:48 +0800 (CST) From: Elaine Zhang To: mturquette@baylibre.com, sboyd@codeaurora.org, heiko@sntech.de Subject: [PATCH v3] clk: fractional-divider: fix up the fractional clk's jitter Date: Fri, 21 Jul 2017 16:03:07 +0800 Message-Id: <1500624187-12165-1-git-send-email-zhangqing@rock-chips.com> X-Mailer: git-send-email 1.9.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20170721_005919_070504_29B1FBB2 X-CRM114-Status: UNSURE ( 7.43 ) X-CRM114-Notice: Please train this message. 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: huangtao@rock-chips.com, xf@rock-chips.com, xxx@rock-chips.com, Elaine Zhang , linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-clk@vger.kernel.org, cl@rock-chips.com MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Fractional dividers may have special requirements concerning numerator and denominator selection that differ from just getting the best approximation. For example on Rockchip socs the denominator must be at least 20 times larger than the numerator to generate precise clock frequencies. Therefore add the ability to provide custom approximation functions, approx = rockchip_fractional_special_approx; but approx = NULL in the default case. RK document description: 3.1.9 Fractional divider usage To get specific frequency, clocks of I2S, SPDIF, UARTcan be generated by fractional divider. Generally you must set that denominator is 20 times larger than numerator to generate precise clock frequency. So the fractional divider applies only to generate low frequency clock like I2S, UART. Signed-off-by: Elaine Zhang --- drivers/clk/clk-fractional-divider.c | 4 ++++ drivers/clk/rockchip/clk.c | 20 ++++++++++++++++++++ include/linux/clk-provider.h | 3 +++ 3 files changed, 27 insertions(+) diff --git a/drivers/clk/clk-fractional-divider.c b/drivers/clk/clk-fractional-divider.c index aab904618eb6..ab2bc229ef2f 100644 --- a/drivers/clk/clk-fractional-divider.c +++ b/drivers/clk/clk-fractional-divider.c @@ -60,6 +60,9 @@ static long clk_fd_round_rate(struct clk_hw *hw, unsigned long rate, if (!rate || rate >= *parent_rate) return *parent_rate; + if (fd->approx) + fd->approx(hw, rate, parent_rate); + /* * Get rate closer to *parent_rate to guarantee there is no overflow * for m and n. In the result it will be the nearest rate left shifted @@ -145,6 +148,7 @@ struct clk_hw *clk_hw_register_fractional_divider(struct device *dev, fd->nmask = GENMASK(nwidth - 1, 0) << nshift; fd->flags = clk_divider_flags; fd->lock = lock; + fd->approx = NULL; fd->hw.init = &init; hw = &fd->hw; diff --git a/drivers/clk/rockchip/clk.c b/drivers/clk/rockchip/clk.c index fe1d393cf678..8b21c5b19107 100644 --- a/drivers/clk/rockchip/clk.c +++ b/drivers/clk/rockchip/clk.c @@ -164,6 +164,25 @@ static int rockchip_clk_frac_notifier_cb(struct notifier_block *nb, return notifier_from_errno(ret); } +/** + * fractional divider must set that denominator is 20 times larger than + * numerator to generate precise clock frequency. + */ +void rockchip_fractional_special_approx(struct clk_hw *hw, + unsigned long rate, + unsigned long *parent_rate) +{ + struct clk_hw *p_parent; + unsigned long p_rate, p_parent_rate; + + p_rate = clk_hw_get_rate(clk_hw_get_parent(hw)); + if ((rate * 20 > p_rate) && (p_rate % rate != 0)) { + p_parent = clk_hw_get_parent(clk_hw_get_parent(hw)); + p_parent_rate = clk_hw_get_rate(p_parent); + *parent_rate = p_parent_rate; + } +} + static struct clk *rockchip_clk_register_frac_branch( struct rockchip_clk_provider *ctx, const char *name, const char *const *parent_names, u8 num_parents, @@ -210,6 +229,7 @@ static struct clk *rockchip_clk_register_frac_branch( div->nwidth = 16; div->nmask = GENMASK(div->nwidth - 1, 0) << div->nshift; div->lock = lock; + div->approx = rockchip_fractional_special_approx; div_ops = &clk_fractional_divider_ops; clk = clk_register_composite(NULL, name, parent_names, num_parents, diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h index a428aec36ace..807262375292 100644 --- a/include/linux/clk-provider.h +++ b/include/linux/clk-provider.h @@ -564,6 +564,9 @@ struct clk_fractional_divider { u8 nwidth; u32 nmask; u8 flags; + void (*approx)(struct clk_hw *hw, + unsigned long rate, + unsigned long *parent_rate); spinlock_t *lock; };