From patchwork Tue Sep 20 23:35:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Maciej W. Rozycki" X-Patchwork-Id: 607915 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 563F0C6FA8E for ; Tue, 20 Sep 2022 23:44:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229738AbiITXoK (ORCPT ); Tue, 20 Sep 2022 19:44:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40664 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229902AbiITXoI (ORCPT ); Tue, 20 Sep 2022 19:44:08 -0400 Received: from angie.orcam.me.uk (angie.orcam.me.uk [78.133.224.34]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id D37E62676; Tue, 20 Sep 2022 16:44:07 -0700 (PDT) Received: by angie.orcam.me.uk (Postfix, from userid 500) id 079E692009C; Wed, 21 Sep 2022 01:35:27 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by angie.orcam.me.uk (Postfix) with ESMTP id 011BB92009B; Wed, 21 Sep 2022 00:35:26 +0100 (BST) Date: Wed, 21 Sep 2022 00:35:26 +0100 (BST) From: "Maciej W. Rozycki" To: Greg Kroah-Hartman , Jiri Slaby cc: Josh Triplett , Anders Blomdell , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v2 0/3] serial: 8250: Let drivers request full 16550A feature probing Message-ID: User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Hi, This is v2 of the series, addressing a small issue pointed out in the original submission and adds a third patch to switch to using BIT_ULL. See individual changes for further details. The original cover letter follows. A recent change has added a SERIAL_8250_16550A_VARIANTS option, which lets one request the 8250 driver not to probe for 16550A device features so as to reduce the driver's device startup time in virtual machines. This has turned out problematic to a more recent update for the OxSemi Tornado series PCIe devices, whose new baud rate generator handling code actually requires switching hardware into the enhanced mode for correct operation, which actually requires 16550A device features to have been probed for. This small patch series fixes the issue by letting individual device subdrivers to request full 16550A device feature probing by means of a flag regardless of the SERIAL_8250_16550A_VARIANTS setting chosen. The changes have been verified with an OXPCIe952 device, in the native UART mode and a 64-bit RISC-V system as well as in the legacy UART mode and a 32-bit x86 system. Credit to Anders for reporting this issue and then working through the resolution. Maciej