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 C2C88C433F5 for ; Tue, 5 Apr 2022 12:57:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1381129AbiDEMy0 (ORCPT ); Tue, 5 Apr 2022 08:54:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43856 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343892AbiDEJOt (ORCPT ); Tue, 5 Apr 2022 05:14:49 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B77FB8EB73; Tue, 5 Apr 2022 02:01:20 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 5AF18B80DA1; Tue, 5 Apr 2022 09:01:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9DDDEC385A0; Tue, 5 Apr 2022 09:01:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649149278; bh=/SISBbLGMqdhm3DxArSAl6lChO08xgYsqYDx0+KrR5g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=AMdFj1dHvX89fRgfoycJ1ezGAC+gAoP7tZOvSxXlH2oNHeG7ZvDYchRACU41u+vGg M3U0+7W8gbKmxcTSlKfhd7NFFVKH8NW240EO+xMWw6R21e8gLht4F3xPMhIiIQhswP FBw+ey3ws/QcPHabttgHzgVw2SFBoxUuaqTBJQL0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Konstantin Aladyshev , Andy Shevchenko , Zev Weiss , Sasha Levin Subject: [PATCH 5.16 0658/1017] serial: 8250_aspeed_vuart: add PORT_ASPEED_VUART port type Date: Tue, 5 Apr 2022 09:26:11 +0200 Message-Id: <20220405070413.814598300@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070354.155796697@linuxfoundation.org> References: <20220405070354.155796697@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Zev Weiss [ Upstream commit a603ca60cebff8589882427a67f870ed946b3fc8 ] 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. Fixes: 54da3e381c2b ("serial: 8250_aspeed_vuart: use UPF_IOREMAP to set up register mapping") Tested-by: Konstantin Aladyshev Reviewed-by: Andy Shevchenko Signed-off-by: Zev Weiss Link: https://lore.kernel.org/r/20220211004203.14915-1-zev@bewilderbeest.net Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- 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 46e2079ad1aa..b34e84695c8c 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..8885e69178bd 100644 --- a/include/uapi/linux/serial_core.h +++ b/include/uapi/linux/serial_core.h @@ -68,6 +68,9 @@ /* NVIDIA Tegra Combined UART */ #define PORT_TEGRA_TCU 41 +/* ASPEED AST2x00 virtual UART */ +#define PORT_ASPEED_VUART 42 + /* Intel EG20 */ #define PORT_PCH_8LINE 44 #define PORT_PCH_2LINE 45 -- 2.34.1