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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,LOTS_OF_MONEY,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 7B8D4C433DF for ; Sun, 17 May 2020 17:36:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 590FE20674 for ; Sun, 17 May 2020 17:36:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=micronovasrl.com header.i=@micronovasrl.com header.b="EpT6X1/S" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726399AbgEQRgV (ORCPT ); Sun, 17 May 2020 13:36:21 -0400 Received: from mail.micronovasrl.com ([212.103.203.10]:58348 "EHLO mail.micronovasrl.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726248AbgEQRgV (ORCPT ); Sun, 17 May 2020 13:36:21 -0400 Received: from mail.micronovasrl.com (mail.micronovasrl.com [127.0.0.1]) by mail.micronovasrl.com (Postfix) with ESMTP id A044AB033E9 for ; Sun, 17 May 2020 19:28:07 +0200 (CEST) Authentication-Results: mail.micronovasrl.com (amavisd-new); dkim=pass reason="pass (just generated, assumed good)" header.d=micronovasrl.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=micronovasrl.com; h=content-transfer-encoding:content-language:content-type :content-type:in-reply-to:mime-version:user-agent:date:date :message-id:from:from:references:to:subject:subject; s=dkim; t= 1589736487; x=1590600488; bh=BTMk5YTSUT9CYUvfxuhhjtuD3oQXc0xwa2+ R9dvv3Gg=; b=EpT6X1/ScxgFvbYJfKKn6NJJuZgEMW2G5vdSm1TPAtTuBkmUC8K 4CFSsVjztkNpEaclA/GQJ8rII93yNEpbu2iQUsHlopcbESyvTRQCBV40Rz3EZJb9 ULJqZ1PVEl/xc6hwXhiCwZ6CBFE6nUF2lsd7z5M/Rg3xFMZ10A0yRLXQ= X-Virus-Scanned: Debian amavisd-new at mail.micronovasrl.com Received: from mail.micronovasrl.com ([127.0.0.1]) by mail.micronovasrl.com (mail.micronovasrl.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id xYKZj1p4JBYJ for ; Sun, 17 May 2020 19:28:07 +0200 (CEST) Received: from [192.168.2.105] (146-241-10-121.dyn.eolo.it [146.241.10.121]) by mail.micronovasrl.com (Postfix) with ESMTPSA id 0F597B033DB; Sun, 17 May 2020 19:28:06 +0200 (CEST) Subject: Re: [PATCH v2 4/7] serial: 8250: Handle implementations not having TEMT interrupt using em485 To: =?UTF-8?Q?Heiko_St=c3=bcbner?= Cc: gregkh@linuxfoundation.org, jslaby@suse.com, andriy.shevchenko@linux.intel.com, matwey.kornilov@gmail.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, lukas@wunner.de, christoph.muellner@theobroma-systems.com References: <20200325231422.1502366-1-heiko@sntech.de> <12195570.sTQbgxCmNy@diego> <3036126.9QgpAzkLCg@diego> From: Giulio Benetti Message-ID: Date: Sun, 17 May 2020 19:28:09 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <3036126.9QgpAzkLCg@diego> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Language: it Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Heiko, Il 17/05/2020 17:04, Heiko Stübner ha scritto: > Hi Giulio, > > Am Donnerstag, 26. März 2020, 03:02:39 CEST schrieb Giulio Benetti: >> Il 26/03/2020 01:05, Heiko Stübner ha scritto: >>> Am Donnerstag, 26. März 2020, 00:47:38 CET schrieb Giulio Benetti: >>>> very cleaner way to handle TEMT as a capability! >>>> And I've found one thing... >>>> >>>> Il 26/03/2020 00:14, Heiko Stuebner ha scritto: >>>>> From: Giulio Benetti >>>>> >>>>> Some 8250 ports have a TEMT interrupt but it's not a part of the 8250 >>>>> standard, instead only available on some implementations. >>>>> >>>>> The current em485 implementation does not work on ports without it. >>>>> The only chance to make it work is to loop-read on LSR register. >>>>> >>>>> So add UART_CAP_TEMT to mark 8250 uarts having this interrupt, >>>>> update all current em485 users with that capability and make >>>>> the stop_tx function loop-read on uarts not having it. >>>>> >>>>> Signed-off-by: Giulio Benetti >>>>> [moved to use added UART_CAP_TEMT, use readx_poll_timeout] >>>>> Signed-off-by: Heiko Stuebner >>>>> --- >>>>> drivers/tty/serial/8250/8250.h | 1 + >>>>> drivers/tty/serial/8250/8250_bcm2835aux.c | 2 +- >>>>> drivers/tty/serial/8250/8250_of.c | 2 ++ >>>>> drivers/tty/serial/8250/8250_omap.c | 2 +- >>>>> drivers/tty/serial/8250/8250_port.c | 25 +++++++++++++++++++---- >>>>> 5 files changed, 26 insertions(+), 6 deletions(-) >>>>> >>>>> diff --git a/drivers/tty/serial/8250/8250.h b/drivers/tty/serial/8250/8250.h >>>>> index 52bb21205bb6..770eb00db497 100644 >>>>> --- a/drivers/tty/serial/8250/8250.h >>>>> +++ b/drivers/tty/serial/8250/8250.h >>>>> @@ -82,6 +82,7 @@ struct serial8250_config { >>>>> #define UART_CAP_MINI (1 << 17) /* Mini UART on BCM283X family lacks: >>>>> * STOP PARITY EPAR SPAR WLEN5 WLEN6 >>>>> */ >>>>> +#define UART_CAP_TEMT (1 << 18) /* UART has TEMT interrupt */ >>>>> >>>>> #define UART_BUG_QUOT (1 << 0) /* UART has buggy quot LSB */ >>>>> #define UART_BUG_TXEN (1 << 1) /* UART has buggy TX IIR status */ >>>>> diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c >>>>> index 12d03e678295..3881242424ca 100644 >>>>> --- a/drivers/tty/serial/8250/8250_bcm2835aux.c >>>>> +++ b/drivers/tty/serial/8250/8250_bcm2835aux.c >>>>> @@ -91,7 +91,7 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev) >>>>> return -ENOMEM; >>>>> >>>>> /* initialize data */ >>>>> - up.capabilities = UART_CAP_FIFO | UART_CAP_MINI; >>>>> + up.capabilities = UART_CAP_FIFO | UART_CAP_MINI | UART_CAP_TEMT; >>>>> up.port.dev = &pdev->dev; >>>>> up.port.regshift = 2; >>>>> up.port.type = PORT_16550; >>>>> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c >>>>> index 65e9045dafe6..841f6fcb2878 100644 >>>>> --- a/drivers/tty/serial/8250/8250_of.c >>>>> +++ b/drivers/tty/serial/8250/8250_of.c >>>>> @@ -225,6 +225,8 @@ static int of_platform_serial_probe(struct platform_device *ofdev) >>>>> &port8250.overrun_backoff_time_ms) != 0) >>>>> port8250.overrun_backoff_time_ms = 0; >>>>> >>>>> + port8250.capabilities |= UART_CAP_TEMT; >>>>> + >>>> >>>> Shouldn't this be NOT UART_CAP_TEMT set by default? On all other >>>> vendor specific files you enable it, I think here you shouldn't enable >>>> it too by default. Right? >>> >>> 8250_of does use the em485 emulation - see of_platform_serial_setup() >>> So I did go by the lazy assumption that any 8250 driver using rs485 >>> before my series always used the interrupt driver code path, so >>> implicitly required to have the TEMT interrupt. >>> >>> Of course, you're right that with the 8250_of maybe not all variants >>> actually do have this interrupt, so falling back to the polling here might >>> be safer. >> >> Probably here it's worth introducing a dt boolean property like >> "temt-capability", then you set or not UART_CAP_TEMT according to its >> presence in dts. This way all cases are covered and we can act >> completely through dts files. >> >> What about that? > > Sorry that this was sitting around for over a month. np at all > I think there are two problems with this: > > (1) this would break backwards compatibility ... right now the whole code > just assumes that everyone does support the TEMT interrupt, so adding > a property to keep it working would break old DTs, which is something that > should not happen ... I guess one option would be to use the inverse > no-temt-interrupt > > (2) uarts handled by 8250_of are still identified by their compatible > though and there is no generic 8250-of compatible, so the > presence / absence of the temt capability should actually just be > bound to the relevant compatible. > > > So my "gut feeling" is to just keep the current way > (was expecting temt-capability before anyway) until an uart > variant without temt comes along I agree with you, what I was proposing is another thing more to do an can be done when needed. Best regards -- Giulio Benetti CTO MICRONOVA SRL Sede: Via A. Niedda 3 - 35010 Vigonza (PD) Tel. 049/8931563 - Fax 049/8931346 Cod.Fiscale - P.IVA 02663420285 Capitale Sociale ¤ 26.000 i.v. Iscritta al Reg. Imprese di Padova N. 02663420285 Numero R.E.A. 258642