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=-4.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 BF74EC282CE for ; Fri, 12 Apr 2019 12:39:42 +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 906C02082E for ; Fri, 12 Apr 2019 12:39:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HxcdNUJI" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 906C02082E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=sntech.de 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=ZWiE4qXfCaKq0j6ILERhZA28oSGeUDNIGXCQhZAaz0g=; b=HxcdNUJIl60RNq VQL3JLSLp1SItRg/3k2BFKTTwnGloUZXTfYZ1yJx+LGbyBZJ3Gpqr4KZl88zPkZfS/ECeoWV/rilr 6ejCsY8Er1wTdqwepMPbMJNb8oGZppMzsNGP7L1HofR7/V4WwrDtIxykPnCJ+ESEtVRGMPrQJ79km +Izg9SMItqMnlH0Gi7sElB+SDc7AyMKdtP4TJUgwZAjRQVNiK9S6Qe1B+FSJ7GKXMddh/40wDtdRG aKT0FigPysGd+kIkDL6cbh9OSDUIWM159ANXT0ZYuye3Y46F9Lrk8n7r9NrfNDt6UMXWTrmWKUUxJ +qs7lNaNWGwGsTD4Tnhw==; 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 1hEvT2-0006rO-Fg; Fri, 12 Apr 2019 12:39:40 +0000 Received: from gloria.sntech.de ([185.11.138.130]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hEvT0-0006r2-1O; Fri, 12 Apr 2019 12:39:39 +0000 Received: from ip5f5a6320.dynamic.kabel-deutschland.de ([95.90.99.32] helo=diego.localnet) by gloria.sntech.de with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1hEvSw-0005aO-ET; Fri, 12 Apr 2019 14:39:34 +0200 From: Heiko =?ISO-8859-1?Q?St=FCbner?= To: Christoph =?ISO-8859-1?Q?M=FCllner?= Subject: Re: [PATCH v1 1/6] clk: rockchip: Add supprot to limit input rate for fractional divider Date: Fri, 12 Apr 2019 14:39:33 +0200 Message-ID: <2068630.7I2iUbhqZj@diego> In-Reply-To: <0e47770b-fa20-74f9-8548-c07aebdcaa53@theobroma-systems.com> References: <1554284549-24916-1-git-send-email-zhangqing@rock-chips.com> <3395739.hcHkC3K37q@diego> <0e47770b-fa20-74f9-8548-c07aebdcaa53@theobroma-systems.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190412_053938_224800_61DD805E X-CRM114-Status: GOOD ( 16.91 ) 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, xxx@rock-chips.com, xf@rock-chips.com, sboyd@kernel.org, mturquette@baylibre.com, Elaine Zhang , linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, Finley Xiao , linux-clk@vger.kernel.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Am Freitag, 12. April 2019, 14:32:08 CEST schrieb Christoph M=FCllner: > = > On 12.04.19 14:21, Heiko St=FCbner wrote: > > Hi Christoph, > > = > > Am Freitag, 12. April 2019, 14:12:52 CEST schrieb Christoph M=FCllner: > >> On 12.04.19 13:52, Heiko St=FCbner wrote: > >>> Am Mittwoch, 3. April 2019, 11:42:24 CEST schrieb Elaine Zhang: > >>>> From: Finley Xiao > >>>> > >>>> From Rockchips fractional divider usage, some clocks can be generated > >>>> by fractional divider, but the input clock frequency of fractional > >>>> divider should be less than a specified value. > >>>> > >>>> Signed-off-by: Finley Xiao > >>>> Signed-off-by: Elaine Zhang > >>> > >>> can you tell me where these maximum input values come from? > >>> > >>> I talked to Christoph from Theobroma (Cc'ed) last week and he mention= ed > >>> that they're using the fractional divider with a higher input frequen= cy > >>> to create a very specific frequency [some details are gone from my me= mory > >>> though] they can't get otherwise. > >>> > >>> So I really don't want to break their working setup by introducing ba= rriers > >>> that are not strictly necessary. > >>> > >>> @Christoph: can you describe the bits from your fractional setup that > >>> I've forgotten please? > >> > >> We need to set the I2S0 clock to 24.56 MHz. > >> > >> When restricting the input frequency to a maximum of 600 Mhz, > >> we could use the integer divider to get 400 Mhz (dividing by 2). > >> However, with the 400 Mhz as input to the frac divider, > >> we run into the problem, that the maximum possible output frequency > >> is 20 MHz (there is another restriction which states that the > >> fraction input : output frequency must be >=3D 20). > > = > > just for clarification, what is the current input frequency you > > already use sucessfully? > = > Our working setup uses the integer divider to reduce to 400 MHz > and uses the frac divider to get something near 24.56 MHz. > I have to admit I have never measured what's on the clock line. Ah ok, so the 600MHz input maximum is ok for your setup and the "< 20" ratio is the question. I thought I remembered you using a higher than 600MHz input rate. [bad memory on my side] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel