From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3CDDA7B for ; Wed, 23 Nov 2022 08:59:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 87B0AC433C1; Wed, 23 Nov 2022 08:59:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669193985; bh=mf8WevELyQ4aEldRiiDOrK5732Sb5lkKpuy2C8/yBTw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=jmt6mYFjl+z6aDIV9Xj5wzNVu8MIQ1nZmEg12yeETmKoTwgoMfK96HHGnvTmOX9Ps 6h8wv1GKOYwexaDoLpvinLcxWZHJ7Eap4yRt6itU1gCRAqcMI3dAQ73X+qqgeAPPij PLEkogkzA51gAtodtm7cWZFFthFCzZP4N8KROHgA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= , Matthias Schiffer , Sasha Levin Subject: [PATCH 4.14 38/88] serial: 8250_omap: remove wait loop from Errata i202 workaround Date: Wed, 23 Nov 2022 09:50:35 +0100 Message-Id: <20221123084549.816907742@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084548.535439312@linuxfoundation.org> References: <20221123084548.535439312@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Matthias Schiffer [ Upstream commit e828e56684d61b17317e0cfdef83791fa61cb76b ] We were occasionally seeing the "Errata i202: timedout" on an AM335x board when repeatedly opening and closing a UART connected to an active sender. As new input may arrive at any time, it is possible to miss the "RX FIFO empty" condition, forcing the loop to wait until it times out. Nothing in the i202 Advisory states that such a wait is even necessary; other FIFO clear functions like serial8250_clear_fifos() do not wait either. For this reason, it seems safe to remove the wait, fixing the mentioned issue. Fixes: 61929cf0169d ("tty: serial: Add 8250-core based omap driver") Reviewed-by: Ilpo Järvinen Signed-off-by: Matthias Schiffer Link: https://lore.kernel.org/r/20221013112339.2540767-1-matthias.schiffer@ew.tq-group.com Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- drivers/tty/serial/8250/8250_omap.c | 17 ----------------- 1 file changed, 17 deletions(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index e32afaa94d36..e4e6b7cb3a16 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -160,27 +160,10 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl) static void omap_8250_mdr1_errataset(struct uart_8250_port *up, struct omap8250_priv *priv) { - u8 timeout = 255; - serial_out(up, UART_OMAP_MDR1, priv->mdr1); udelay(2); serial_out(up, UART_FCR, up->fcr | UART_FCR_CLEAR_XMIT | UART_FCR_CLEAR_RCVR); - /* - * Wait for FIFO to empty: when empty, RX_FIFO_E bit is 0 and - * TX_FIFO_E bit is 1. - */ - while (UART_LSR_THRE != (serial_in(up, UART_LSR) & - (UART_LSR_THRE | UART_LSR_DR))) { - timeout--; - if (!timeout) { - /* Should *never* happen. we warn and carry on */ - dev_crit(up->port.dev, "Errata i202: timedout %x\n", - serial_in(up, UART_LSR)); - break; - } - udelay(1); - } } static void omap_8250_get_divisor(struct uart_port *port, unsigned int baud, -- 2.35.1