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 A0A4CC433EF for ; Thu, 10 Feb 2022 09:22:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238462AbiBJJWO (ORCPT ); Thu, 10 Feb 2022 04:22:14 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:47298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235335AbiBJJWL (ORCPT ); Thu, 10 Feb 2022 04:22:11 -0500 Received: from thorn.bewilderbeest.net (thorn.bewilderbeest.net [IPv6:2605:2700:0:5::4713:9cab]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4856E1039; Thu, 10 Feb 2022 01:22:13 -0800 (PST) Received: from hatter.bewilderbeest.net (174-21-187-98.tukw.qwest.net [174.21.187.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: zev) by thorn.bewilderbeest.net (Postfix) with ESMTPSA id 537DA283; Thu, 10 Feb 2022 01:22:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bewilderbeest.net; s=thorn; t=1644484932; bh=YYp49ln6qDD6oDwCC4EQTXa3MheUKZJ27LXDjoYZpLo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZwHj0U8EiiyLti7wh/GpeLfS81YfJ6qhA6Ey/xOmQV3Gt9+jRIjd3mg9Rw+bTMpth BqMOB3Dbr0+KfEsXwqR0OrA3aopUioSA+oQfisTOCb0hBwZ7hzsmo0FlVlonFLJQgo NHNkku0Sf1uc7IcnysI2wiJ6hQ0X8TcUKvmOmYtg= Date: Thu, 10 Feb 2022 01:22:09 -0800 From: Zev Weiss To: Greg Kroah-Hartman Cc: Joel Stanley , Andrew Jeffery , Jiri Slaby , Andy Shevchenko , Konstantin Aladyshev , Oskar Senft , openbmc@lists.ozlabs.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] serial: 8250_aspeed_vuart: add PORT_ASPEED_VUART port type Message-ID: References: <20220209203414.23491-1-zev@bewilderbeest.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 10, 2022 at 12:20:12AM PST, Greg Kroah-Hartman wrote: >On Wed, Feb 09, 2022 at 11:49:47PM -0800, Zev Weiss wrote: >> On Wed, Feb 09, 2022 at 11:40:42PM PST, Greg Kroah-Hartman wrote: >> > On Wed, Feb 09, 2022 at 12:34:14PM -0800, Zev Weiss wrote: >> > > Commit 54da3e381c2b ("serial: 8250_aspeed_vuart: use UPF_IOREMAP to >> > > set up register mapping") fixed a bug that had, as a side-effect, >> > > prevented the 8250_aspeed_vuart driver from enabling the VUART's >> > > FIFOs. However, fixing that (and hence enabling the FIFOs) has in >> > > turn revealed what appears to be a hardware bug in the ASPEED VUART in >> > > which the host-side THRE bit doesn't get if the BMC-side receive FIFO >> > > trigger level is set to anything but one byte. This causes problems >> > > for polled-mode writes from the host -- for example, Linux kernel >> > > console writes proceed at a glacial pace (less than 100 bytes per >> > > second) because the write path waits for a 10ms timeout to expire >> > > after every character instead of being able to continue on to the next >> > > character upon seeing THRE asserted. (GRUB behaves similarly.) >> > > >> > > As a workaround, introduce a new port type for the ASPEED VUART that's >> > > identical to PORT_16550A as it had previously been using, but with >> > > UART_FCR_R_TRIG_00 instead to set the receive FIFO trigger level to >> > > one byte, which (experimentally) seems to avoid the problematic THRE >> > > behavior. >> > > >> > > Signed-off-by: Zev Weiss >> > > Tested-by: Konstantin Aladyshev >> > >> > Do we need a "Fixes:" tag here as well? >> >> I was wondering the same -- I left it out because it didn't seem like it was >> strictly a bug in the earlier commit that's really being fixed per se, but >> perhaps that's an overly pedantic distinction. I can certainly add it if >> you'd prefer. > >This obviously fixes an issue, if you don't have a specific commit that >caused it, a cc: stable@vger.kernel.org should be added so we know to >backport this to all stable kernels. > Okay -- well, I suppose it's a fix in the sense that if you have the earlier commit, you'll also want this one, so I'll add the tag. >> >> > >> > > --- >> > > drivers/tty/serial/8250/8250_aspeed_vuart.c | 2 +- >> > > drivers/tty/serial/8250/8250_port.c | 8 ++++++++ >> > > include/uapi/linux/serial_core.h | 3 +++ >> > > 3 files changed, 12 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > index 2350fb3bb5e4..c2cecc6f47db 100644 >> > > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > @@ -487,7 +487,7 @@ static int aspeed_vuart_probe(struct platform_device *pdev) >> > > port.port.irq = irq_of_parse_and_map(np, 0); >> > > port.port.handle_irq = aspeed_vuart_handle_irq; >> > > port.port.iotype = UPIO_MEM; >> > > - port.port.type = PORT_16550A; >> > > + port.port.type = PORT_ASPEED_VUART; >> > > port.port.uartclk = clk; >> > > port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP >> > > | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST; >> > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c >> > > index 3b12bfc1ed67..973870ebff69 100644 >> > > --- a/drivers/tty/serial/8250/8250_port.c >> > > +++ b/drivers/tty/serial/8250/8250_port.c >> > > @@ -307,6 +307,14 @@ static const struct serial8250_config uart_config[] = { >> > > .rxtrig_bytes = {1, 32, 64, 112}, >> > > .flags = UART_CAP_FIFO | UART_CAP_SLEEP, >> > > }, >> > > + [PORT_ASPEED_VUART] = { >> > > + .name = "ASPEED VUART", >> > > + .fifo_size = 16, >> > > + .tx_loadsz = 16, >> > > + .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00, >> > > + .rxtrig_bytes = {1, 4, 8, 14}, >> > > + .flags = UART_CAP_FIFO, >> > > + }, >> > > }; >> > > >> > > /* Uart divisor latch read */ >> > > diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h >> > > index c4042dcfdc0c..cd11748833e6 100644 >> > > --- a/include/uapi/linux/serial_core.h >> > > +++ b/include/uapi/linux/serial_core.h >> > > @@ -274,4 +274,7 @@ >> > > /* Freescale LINFlexD UART */ >> > > #define PORT_LINFLEXUART 122 >> > > >> > > +/* ASPEED AST2x00 virtual UART */ >> > > +#define PORT_ASPEED_VUART 123 >> > >> > Why does this value have to be in a uapi header file? What userspace >> > tool is going to need this? >> > >> >> I only put it there because that was where all the other port type constants >> were defined, and wondered the same thing about the lot of them. Is there a >> userspace tool that makes use of any of these? > >Not really, please don't add it if you do not require it. > It seems like an odd inconsistency to put this one particular definition somewhere else when the other 100+ of its siblings are in the uapi header; would you want a preceding patch to move them all somewhere under include/linux? (Which in turn doesn't really seem like a change for -stable I'd think.) Though actually, on further investigation I see those constants are in fact exposed to userspace in struct serial_struct->type (via TIOCGSERIAL/TIOCSSERIAL), and via the 'type' sysfs attribute, so I'd think we'd probably want to keep them as they are? Zev 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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 36F29C433EF for ; Thu, 10 Feb 2022 09:23:00 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4JvWW61bK9z3bdG for ; Thu, 10 Feb 2022 20:22:58 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=bewilderbeest.net header.i=@bewilderbeest.net header.a=rsa-sha256 header.s=thorn header.b=ZwHj0U8E; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=bewilderbeest.net (client-ip=71.19.156.171; helo=thorn.bewilderbeest.net; envelope-from=zev@bewilderbeest.net; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=bewilderbeest.net header.i=@bewilderbeest.net header.a=rsa-sha256 header.s=thorn header.b=ZwHj0U8E; dkim-atps=neutral X-Greylist: delayed 46056 seconds by postgrey-1.36 at boromir; Thu, 10 Feb 2022 20:22:14 AEDT Received: from thorn.bewilderbeest.net (thorn.bewilderbeest.net [71.19.156.171]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4JvWVG74mLz3bSv; Thu, 10 Feb 2022 20:22:14 +1100 (AEDT) Received: from hatter.bewilderbeest.net (174-21-187-98.tukw.qwest.net [174.21.187.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: zev) by thorn.bewilderbeest.net (Postfix) with ESMTPSA id 537DA283; Thu, 10 Feb 2022 01:22:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bewilderbeest.net; s=thorn; t=1644484932; bh=YYp49ln6qDD6oDwCC4EQTXa3MheUKZJ27LXDjoYZpLo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZwHj0U8EiiyLti7wh/GpeLfS81YfJ6qhA6Ey/xOmQV3Gt9+jRIjd3mg9Rw+bTMpth BqMOB3Dbr0+KfEsXwqR0OrA3aopUioSA+oQfisTOCb0hBwZ7hzsmo0FlVlonFLJQgo NHNkku0Sf1uc7IcnysI2wiJ6hQ0X8TcUKvmOmYtg= Date: Thu, 10 Feb 2022 01:22:09 -0800 From: Zev Weiss To: Greg Kroah-Hartman Subject: Re: [PATCH] serial: 8250_aspeed_vuart: add PORT_ASPEED_VUART port type Message-ID: References: <20220209203414.23491-1-zev@bewilderbeest.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aspeed@lists.ozlabs.org, Konstantin Aladyshev , Andrew Jeffery , openbmc@lists.ozlabs.org, linux-kernel@vger.kernel.org, Oskar Senft , linux-serial@vger.kernel.org, Andy Shevchenko , Jiri Slaby , linux-arm-kernel@lists.infradead.org Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" On Thu, Feb 10, 2022 at 12:20:12AM PST, Greg Kroah-Hartman wrote: >On Wed, Feb 09, 2022 at 11:49:47PM -0800, Zev Weiss wrote: >> On Wed, Feb 09, 2022 at 11:40:42PM PST, Greg Kroah-Hartman wrote: >> > On Wed, Feb 09, 2022 at 12:34:14PM -0800, Zev Weiss wrote: >> > > Commit 54da3e381c2b ("serial: 8250_aspeed_vuart: use UPF_IOREMAP to >> > > set up register mapping") fixed a bug that had, as a side-effect, >> > > prevented the 8250_aspeed_vuart driver from enabling the VUART's >> > > FIFOs. However, fixing that (and hence enabling the FIFOs) has in >> > > turn revealed what appears to be a hardware bug in the ASPEED VUART in >> > > which the host-side THRE bit doesn't get if the BMC-side receive FIFO >> > > trigger level is set to anything but one byte. This causes problems >> > > for polled-mode writes from the host -- for example, Linux kernel >> > > console writes proceed at a glacial pace (less than 100 bytes per >> > > second) because the write path waits for a 10ms timeout to expire >> > > after every character instead of being able to continue on to the next >> > > character upon seeing THRE asserted. (GRUB behaves similarly.) >> > > >> > > As a workaround, introduce a new port type for the ASPEED VUART that's >> > > identical to PORT_16550A as it had previously been using, but with >> > > UART_FCR_R_TRIG_00 instead to set the receive FIFO trigger level to >> > > one byte, which (experimentally) seems to avoid the problematic THRE >> > > behavior. >> > > >> > > Signed-off-by: Zev Weiss >> > > Tested-by: Konstantin Aladyshev >> > >> > Do we need a "Fixes:" tag here as well? >> >> I was wondering the same -- I left it out because it didn't seem like it was >> strictly a bug in the earlier commit that's really being fixed per se, but >> perhaps that's an overly pedantic distinction. I can certainly add it if >> you'd prefer. > >This obviously fixes an issue, if you don't have a specific commit that >caused it, a cc: stable@vger.kernel.org should be added so we know to >backport this to all stable kernels. > Okay -- well, I suppose it's a fix in the sense that if you have the earlier commit, you'll also want this one, so I'll add the tag. >> >> > >> > > --- >> > > drivers/tty/serial/8250/8250_aspeed_vuart.c | 2 +- >> > > drivers/tty/serial/8250/8250_port.c | 8 ++++++++ >> > > include/uapi/linux/serial_core.h | 3 +++ >> > > 3 files changed, 12 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > index 2350fb3bb5e4..c2cecc6f47db 100644 >> > > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > @@ -487,7 +487,7 @@ static int aspeed_vuart_probe(struct platform_device *pdev) >> > > port.port.irq = irq_of_parse_and_map(np, 0); >> > > port.port.handle_irq = aspeed_vuart_handle_irq; >> > > port.port.iotype = UPIO_MEM; >> > > - port.port.type = PORT_16550A; >> > > + port.port.type = PORT_ASPEED_VUART; >> > > port.port.uartclk = clk; >> > > port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP >> > > | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST; >> > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c >> > > index 3b12bfc1ed67..973870ebff69 100644 >> > > --- a/drivers/tty/serial/8250/8250_port.c >> > > +++ b/drivers/tty/serial/8250/8250_port.c >> > > @@ -307,6 +307,14 @@ static const struct serial8250_config uart_config[] = { >> > > .rxtrig_bytes = {1, 32, 64, 112}, >> > > .flags = UART_CAP_FIFO | UART_CAP_SLEEP, >> > > }, >> > > + [PORT_ASPEED_VUART] = { >> > > + .name = "ASPEED VUART", >> > > + .fifo_size = 16, >> > > + .tx_loadsz = 16, >> > > + .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00, >> > > + .rxtrig_bytes = {1, 4, 8, 14}, >> > > + .flags = UART_CAP_FIFO, >> > > + }, >> > > }; >> > > >> > > /* Uart divisor latch read */ >> > > diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h >> > > index c4042dcfdc0c..cd11748833e6 100644 >> > > --- a/include/uapi/linux/serial_core.h >> > > +++ b/include/uapi/linux/serial_core.h >> > > @@ -274,4 +274,7 @@ >> > > /* Freescale LINFlexD UART */ >> > > #define PORT_LINFLEXUART 122 >> > > >> > > +/* ASPEED AST2x00 virtual UART */ >> > > +#define PORT_ASPEED_VUART 123 >> > >> > Why does this value have to be in a uapi header file? What userspace >> > tool is going to need this? >> > >> >> I only put it there because that was where all the other port type constants >> were defined, and wondered the same thing about the lot of them. Is there a >> userspace tool that makes use of any of these? > >Not really, please don't add it if you do not require it. > It seems like an odd inconsistency to put this one particular definition somewhere else when the other 100+ of its siblings are in the uapi header; would you want a preceding patch to move them all somewhere under include/linux? (Which in turn doesn't really seem like a change for -stable I'd think.) Though actually, on further investigation I see those constants are in fact exposed to userspace in struct serial_struct->type (via TIOCGSERIAL/TIOCSSERIAL), and via the 'type' sysfs attribute, so I'd think we'd probably want to keep them as they are? Zev 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id CEE8CC433F5 for ; Thu, 10 Feb 2022 09:23:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=VXDeknf0mJDMyO8vLypI+A4lWRJ8hl3xrp51tOCPg2o=; b=oowAcE1Y1JlVkuU1D7XGmpd3eh u/TsTQ+nueRS+vJm2nOhPL78OmevYSGI5MbkK3KN7y5yLDQbQ53e9O5wJkJVbvd3mNvOaLjEOvnpp t3Qr3F97yG14iehUvJNCyXTX1mzrZEmOLxr5tPMLkeg5NoYFQJhB6mPyFUwEt8WwUEeQhQM6yjy2F IGqDQS2FZqh27z/Gj+CjNmb1wxc4Q9A26N1mg5CG85Ja8REvECHIKTruJdUTRsKVCE94nqd9POWa3 E4Zt/Vx3xPcotz5JQwPIqE4/GoZQKtLZSu4ZG7alhSNpItEEAZQfwe31u9Vk1G6o0KihPPF2sXho4 QSR06LCw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nI5ec-003GLJ-Fi; Thu, 10 Feb 2022 09:22:18 +0000 Received: from thorn.bewilderbeest.net ([2605:2700:0:5::4713:9cab]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nI5eZ-003GKT-5r for linux-arm-kernel@lists.infradead.org; Thu, 10 Feb 2022 09:22:17 +0000 Received: from hatter.bewilderbeest.net (174-21-187-98.tukw.qwest.net [174.21.187.98]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: zev) by thorn.bewilderbeest.net (Postfix) with ESMTPSA id 537DA283; Thu, 10 Feb 2022 01:22:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bewilderbeest.net; s=thorn; t=1644484932; bh=YYp49ln6qDD6oDwCC4EQTXa3MheUKZJ27LXDjoYZpLo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ZwHj0U8EiiyLti7wh/GpeLfS81YfJ6qhA6Ey/xOmQV3Gt9+jRIjd3mg9Rw+bTMpth BqMOB3Dbr0+KfEsXwqR0OrA3aopUioSA+oQfisTOCb0hBwZ7hzsmo0FlVlonFLJQgo NHNkku0Sf1uc7IcnysI2wiJ6hQ0X8TcUKvmOmYtg= Date: Thu, 10 Feb 2022 01:22:09 -0800 From: Zev Weiss To: Greg Kroah-Hartman Cc: Joel Stanley , Andrew Jeffery , Jiri Slaby , Andy Shevchenko , Konstantin Aladyshev , Oskar Senft , openbmc@lists.ozlabs.org, linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] serial: 8250_aspeed_vuart: add PORT_ASPEED_VUART port type Message-ID: References: <20220209203414.23491-1-zev@bewilderbeest.net> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220210_012215_260270_EEF0539B X-CRM114-Status: GOOD ( 40.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Feb 10, 2022 at 12:20:12AM PST, Greg Kroah-Hartman wrote: >On Wed, Feb 09, 2022 at 11:49:47PM -0800, Zev Weiss wrote: >> On Wed, Feb 09, 2022 at 11:40:42PM PST, Greg Kroah-Hartman wrote: >> > On Wed, Feb 09, 2022 at 12:34:14PM -0800, Zev Weiss wrote: >> > > Commit 54da3e381c2b ("serial: 8250_aspeed_vuart: use UPF_IOREMAP to >> > > set up register mapping") fixed a bug that had, as a side-effect, >> > > prevented the 8250_aspeed_vuart driver from enabling the VUART's >> > > FIFOs. However, fixing that (and hence enabling the FIFOs) has in >> > > turn revealed what appears to be a hardware bug in the ASPEED VUART in >> > > which the host-side THRE bit doesn't get if the BMC-side receive FIFO >> > > trigger level is set to anything but one byte. This causes problems >> > > for polled-mode writes from the host -- for example, Linux kernel >> > > console writes proceed at a glacial pace (less than 100 bytes per >> > > second) because the write path waits for a 10ms timeout to expire >> > > after every character instead of being able to continue on to the next >> > > character upon seeing THRE asserted. (GRUB behaves similarly.) >> > > >> > > As a workaround, introduce a new port type for the ASPEED VUART that's >> > > identical to PORT_16550A as it had previously been using, but with >> > > UART_FCR_R_TRIG_00 instead to set the receive FIFO trigger level to >> > > one byte, which (experimentally) seems to avoid the problematic THRE >> > > behavior. >> > > >> > > Signed-off-by: Zev Weiss >> > > Tested-by: Konstantin Aladyshev >> > >> > Do we need a "Fixes:" tag here as well? >> >> I was wondering the same -- I left it out because it didn't seem like it was >> strictly a bug in the earlier commit that's really being fixed per se, but >> perhaps that's an overly pedantic distinction. I can certainly add it if >> you'd prefer. > >This obviously fixes an issue, if you don't have a specific commit that >caused it, a cc: stable@vger.kernel.org should be added so we know to >backport this to all stable kernels. > Okay -- well, I suppose it's a fix in the sense that if you have the earlier commit, you'll also want this one, so I'll add the tag. >> >> > >> > > --- >> > > drivers/tty/serial/8250/8250_aspeed_vuart.c | 2 +- >> > > drivers/tty/serial/8250/8250_port.c | 8 ++++++++ >> > > include/uapi/linux/serial_core.h | 3 +++ >> > > 3 files changed, 12 insertions(+), 1 deletion(-) >> > > >> > > diff --git a/drivers/tty/serial/8250/8250_aspeed_vuart.c b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > index 2350fb3bb5e4..c2cecc6f47db 100644 >> > > --- a/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > +++ b/drivers/tty/serial/8250/8250_aspeed_vuart.c >> > > @@ -487,7 +487,7 @@ static int aspeed_vuart_probe(struct platform_device *pdev) >> > > port.port.irq = irq_of_parse_and_map(np, 0); >> > > port.port.handle_irq = aspeed_vuart_handle_irq; >> > > port.port.iotype = UPIO_MEM; >> > > - port.port.type = PORT_16550A; >> > > + port.port.type = PORT_ASPEED_VUART; >> > > port.port.uartclk = clk; >> > > port.port.flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP >> > > | UPF_FIXED_PORT | UPF_FIXED_TYPE | UPF_NO_THRE_TEST; >> > > diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c >> > > index 3b12bfc1ed67..973870ebff69 100644 >> > > --- a/drivers/tty/serial/8250/8250_port.c >> > > +++ b/drivers/tty/serial/8250/8250_port.c >> > > @@ -307,6 +307,14 @@ static const struct serial8250_config uart_config[] = { >> > > .rxtrig_bytes = {1, 32, 64, 112}, >> > > .flags = UART_CAP_FIFO | UART_CAP_SLEEP, >> > > }, >> > > + [PORT_ASPEED_VUART] = { >> > > + .name = "ASPEED VUART", >> > > + .fifo_size = 16, >> > > + .tx_loadsz = 16, >> > > + .fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_00, >> > > + .rxtrig_bytes = {1, 4, 8, 14}, >> > > + .flags = UART_CAP_FIFO, >> > > + }, >> > > }; >> > > >> > > /* Uart divisor latch read */ >> > > diff --git a/include/uapi/linux/serial_core.h b/include/uapi/linux/serial_core.h >> > > index c4042dcfdc0c..cd11748833e6 100644 >> > > --- a/include/uapi/linux/serial_core.h >> > > +++ b/include/uapi/linux/serial_core.h >> > > @@ -274,4 +274,7 @@ >> > > /* Freescale LINFlexD UART */ >> > > #define PORT_LINFLEXUART 122 >> > > >> > > +/* ASPEED AST2x00 virtual UART */ >> > > +#define PORT_ASPEED_VUART 123 >> > >> > Why does this value have to be in a uapi header file? What userspace >> > tool is going to need this? >> > >> >> I only put it there because that was where all the other port type constants >> were defined, and wondered the same thing about the lot of them. Is there a >> userspace tool that makes use of any of these? > >Not really, please don't add it if you do not require it. > It seems like an odd inconsistency to put this one particular definition somewhere else when the other 100+ of its siblings are in the uapi header; would you want a preceding patch to move them all somewhere under include/linux? (Which in turn doesn't really seem like a change for -stable I'd think.) Though actually, on further investigation I see those constants are in fact exposed to userspace in struct serial_struct->type (via TIOCGSERIAL/TIOCSSERIAL), and via the 'type' sysfs attribute, so I'd think we'd probably want to keep them as they are? Zev _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel