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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B66ECC6778A for ; Tue, 3 Jul 2018 13:03:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6F56F24BBA for ; Tue, 3 Jul 2018 13:03:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6F56F24BBA Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753355AbeGCNDF (ORCPT ); Tue, 3 Jul 2018 09:03:05 -0400 Received: from mga11.intel.com ([192.55.52.93]:7805 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752494AbeGCNDD (ORCPT ); Tue, 3 Jul 2018 09:03:03 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Jul 2018 06:03:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.51,303,1526367600"; d="scan'208";a="53741311" Received: from smile.fi.intel.com (HELO smile) ([10.237.72.86]) by orsmga007.jf.intel.com with ESMTP; 03 Jul 2018 06:02:58 -0700 Message-ID: Subject: Re: [PATCH 0/2] serial: 8250_dw: add fractional divisor support From: Andy Shevchenko To: Jisheng Zhang Cc: Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Date: Tue, 03 Jul 2018 16:02:57 +0300 In-Reply-To: <20180703102257.678db6a8@xhacker.debian> References: <20180702180428.331b36c5@xhacker.debian> <59b14f97234271a7d859fa07f27bd66ec252ccc9.camel@linux.intel.com> <20180703102257.678db6a8@xhacker.debian> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.1-2 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2018-07-03 at 10:22 +0800, Jisheng Zhang wrote: > Hi, > > On Mon, 2 Jul 2018 14:51:03 +0300 Andy Shevchenko wrote: > > > On Mon, 2018-07-02 at 13:18 +0300, Andy Shevchenko wrote: > > > On Mon, 2018-07-02 at 18:04 +0800, Jisheng Zhang wrote: > > > > For Synopsys DesignWare 8250 uart which version >= 4.00a, > > > > there's a > > > > valid divisor latch fraction register. The fractional divisor > > > > width > > > > is > > > > 4bits ~ 6bits. > > > > > > > > > > There are several serial IPs that have fractional divider built- > > > in. > > > None > > > is using any specific hooks. Why do you need in your case, esp. > > > taking > > > into consideration that we have a custom ->set_termios() > > > callback? > > > > Okay, I see that in 8250 we have hooks embedded into 8250_port.c > > which > > is not the best solution. > > > > For example it prevents better splitting Exar code. > > So, we would need these hooks, but better to integrate them in the > > same > > way like it's done for the rest of 8250 ones, i.e. > > - rename existing to have a "do" word > > - create new functions which would be a replacement that choose > > between > > "do" variant and custom one > > - not sure if we need to export "do" variants (at least for now) > > So you mean add the support as following: > > 1.rename current serial8250_set_divisor as serial8250_do_set_divisor > Yes > 2.add a new serial8250_set_divisor which will be as simple as Yes and no. > > static void serial8250_set_divisor(struct uart_port *port, ...) > { > struct uart_8250_port *up = up_to_u8250p(port); > > if (up->set_divisor) port-> > up->set_divisor(...); port-> > else > serial8250_do_set_divisor(...); > } > > could you please confirm? Yes. > > Another issue is I'm not sure which struct to add the hook, > struct uart_port or struct uart_8250_port? Currently, it seems that > only > uart_8250_port needs this hook, Define "needs". 8250 _uses_ it, the rest which I easy grepped would be able to use it if we provide such a possibility. lantiq.c is one example (currently they don't use it), or drivers/tty/serial/digicolor-usart.c limits baud rate choice b/c of absence of a common way. > sure, adding the hook to struct uart_port > is fine either. Could you please kindly give some suggestions? See above. Thanks for doing this! > > Thanks, > Jisheng -- Andy Shevchenko Intel Finland Oy