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 E3493C4167B for ; Mon, 4 Dec 2023 13:20:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233838AbjLDNUK (ORCPT ); Mon, 4 Dec 2023 08:20:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233171AbjLDNUI (ORCPT ); Mon, 4 Dec 2023 08:20:08 -0500 Received: from mgamail.intel.com (mgamail.intel.com [134.134.136.24]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A7AFA1; Mon, 4 Dec 2023 05:20:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1701696015; x=1733232015; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=4NPXnux+c7mfmuxeW1NdbPlpm/f/3Pww4CWNNGCbIWw=; b=Q8auie4nwj65b8xzmnA7s6ko+WGC/N2slbZg3Rl0xiM2XhFFDyBZZXUF Ip/1yz5WFIyp6Af5j3TIqBAzxa8gu49sM10h16+yaUKmlhrQDciY+j8jh fQVtWOUbjIPv93g2ZRhcsaLzbxPWTEAbCv1Fz/p/1bpkfPzLMr5XqiXZ4 JFCjxcz1kec9lOXqsqUIJ75VFftcOo3BuQGc8b4h86vaTN7oeCiBsiGne 2t6NklBRbV0NHrAMZk1flo+leysn4rMkUBPmordLb0FulMMUCoQB0ykWI DPi1mMH5B1zzdAfzKczTKsJ1NLd+DHf5zHauXpesbRlwGVBLjcf3+M7ph g==; X-IronPort-AV: E=McAfee;i="6600,9927,10913"; a="396535976" X-IronPort-AV: E=Sophos;i="6.04,249,1695711600"; d="scan'208";a="396535976" Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Dec 2023 05:20:14 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6600,9927,10913"; a="770534305" X-IronPort-AV: E=Sophos;i="6.04,249,1695711600"; d="scan'208";a="770534305" Received: from malladhi-mobl.gar.corp.intel.com ([10.249.34.28]) by orsmga002-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Dec 2023 05:20:12 -0800 Date: Mon, 4 Dec 2023 15:20:09 +0200 (EET) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Dawei Li cc: Greg Kroah-Hartman , Andy Shevchenko , Jiri Slaby , jszhang@kernel.org, LKML , linux-serial , set_pte_at@outlook.com, stable@kernel.org Subject: Re: [PATCH] serial: dw8250: Make DLF feature independent of ADDITIONAL_FEATURE In-Reply-To: <20231204130820.2823688-1-dawei.li@shingroup.cn> Message-ID: <48f6fcce-4b5-a7c0-2fc0-989b9a2fba8@linux.intel.com> References: <20231204130820.2823688-1-dawei.li@shingroup.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 4 Dec 2023, Dawei Li wrote: > DW apb uart databook defines couples of configuration parameters of > dw8250 IP, among which there are 2 of them: > - ADDTIONAL_FEATURE > " Configure the peripheral to have the option to include FIFO status > registers, shadow registers and encoded parameter register. Also > configures the peripheral to have UART component version and the > peripheral ID registers. " > > - FRACTIONAL_BAUD_DIVISOR_EN > " Configures the peripheral to have Fractional Baud Rate Divisor. > .... " > > These two parameters are completely irrelevant, and supposed to be > independent of each other. However, in current dw8250 driver > implementation, they are hooked together. > > The bug was hit when we are bringing up dw8250 IP on our hardware > platform, in which parameters are configured in such combination: > - ADDTIONAL_FEATURE disabled; > - FRACTIONAL_BAUD_DIVISOR_EN enabled; > > Fixes: 701c5e73b296 ("serial: 8250_dw: add fractional divisor support") > Cc: stable@kernel.org > Signed-off-by: Dawei Li > --- > drivers/tty/serial/8250/8250_dwlib.c | 22 +++++++++++----------- > 1 file changed, 11 insertions(+), 11 deletions(-) > > diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c > index 84843e204a5e..136ad093c5b6 100644 > --- a/drivers/tty/serial/8250/8250_dwlib.c > +++ b/drivers/tty/serial/8250/8250_dwlib.c > @@ -259,17 +259,6 @@ void dw8250_setup_port(struct uart_port *p) > } > up->capabilities |= UART_CAP_NOTEMT; > > - /* > - * If the Component Version Register returns zero, we know that > - * ADDITIONAL_FEATURES are not enabled. No need to go any further. > - */ > - reg = dw8250_readl_ext(p, DW_UART_UCV); > - if (!reg) > - return; > - > - dev_dbg(p->dev, "Designware UART version %c.%c%c\n", > - (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); > - > /* Preserve value written by firmware or bootloader */ > old_dlf = dw8250_readl_ext(p, DW_UART_DLF); > dw8250_writel_ext(p, DW_UART_DLF, ~0U); > @@ -282,6 +271,17 @@ void dw8250_setup_port(struct uart_port *p) > p->set_divisor = dw8250_set_divisor; > } > > + /* > + * If the Component Version Register returns zero, we know that > + * ADDITIONAL_FEATURES are not enabled. No need to go any further. > + */ > + reg = dw8250_readl_ext(p, DW_UART_UCV); > + if (!reg) > + return; > + > + dev_dbg(p->dev, "Designware UART version %c.%c%c\n", > + (reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff); > + > reg = dw8250_readl_ext(p, DW_UART_CPR); > if (!reg) { > reg = data->pdata->cpr_val; > The very same code change is already in tty-next (from another author). -- i.