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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 038FDC54E94 for ; Thu, 26 Jan 2023 07:51:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235633AbjAZHvo (ORCPT ); Thu, 26 Jan 2023 02:51:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35578 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234698AbjAZHvn (ORCPT ); Thu, 26 Jan 2023 02:51:43 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C3F488698 for ; Wed, 25 Jan 2023 23:51:42 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 5C67361755 for ; Thu, 26 Jan 2023 07:51:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 51479C433EF; Thu, 26 Jan 2023 07:51:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1674719501; bh=Hv11EF/3zUhlPCt+x+0Flls6D9QmZx79MA8wZ2wG1ao=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=R4IHDgRmsS+nPAiqJrR7Aq8O/4l/XYuXvwgnSMeK2SssoYQZdIUc/2fvlaeJFXvyz Ws5YJYHfeevhnvhz01kA65COtfZO6nkZzUKCQlGuurLgjJo4nROT+7dCkfCnEjgImv u6V+aeCR37kGZmF2uHS4IIVyXnHbWbZaU1dK9go6dpWdserqWf5jmjGsfjgCPvT0/b 4TNGd1p37MId/YQHnK5JTN21F2hs7USqmiN1h/lXNterekRv5cFnFqyfN6D2VqXWuG ERSsCIx4iDMU6sEyeBWzg4h5FwQEUQM1NuLearZyNUbM/RbZW7SZilnyXA2gO8Phb7 T5ubZjFgUwUng== Date: Thu, 26 Jan 2023 15:51:33 +0800 From: Shawn Guo To: Marek Vasut Cc: linux-arm-kernel@lists.infradead.org, Christoph Niedermaier , Fabio Estevam , Krzysztof Kozlowski , NXP Linux Team , Peng Fan , Pengutronix Kernel Team , Rob Herring , Sascha Hauer , devicetree@vger.kernel.org Subject: Re: [PATCH] arm64: dts: imx8mp: Improve bluetooth UART on DH electronics i.MX8M Plus DHCOM Message-ID: <20230126075132.GA20713@T480> References: <20230117223942.130170-1-marex@denx.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230117223942.130170-1-marex@denx.de> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Tue, Jan 17, 2023 at 11:39:42PM +0100, Marek Vasut wrote: > Use PLL1_80M instead of PLL3 to drive UART2 clock divided down to 80 MHz > instead of 64 MHz to obtain suitable block clock for exact 4 Mbdps, which > is the maximum supported baud rate by the muRata 2AE BT UART. > > The difference here is that at 64 MHz UART block clock, the clock with are > divided by 16 (due to oversampling) to 4 MHz and the baud rate generator > then needs to be set to UBIR+1/UBMR+1 = 1/1 to yield 4 Mbdps . In case of > 80 MHz UART block clock divided by 16 to 5 MHz, the baud rate generator > needs to be set to UBIR+1/UBMR+1 = 4/5 to yield 4 Mbdps . > > Both options are valid and yield the same result, except using the PLL1_80M > output requires fewer clock tree changes, since the PLL1 already generates > the 80 MHz usable for UART, which frees the PLL3 for other uses. > > Suggested-by: Christoph Niedermaier > Signed-off-by: Marek Vasut Applied, thanks!