From patchwork Tue Jun 22 14:57:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vignesh Raghavendra X-Patchwork-Id: 12337761 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=-19.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT 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 9BE52C2B9F4 for ; Tue, 22 Jun 2021 14:57:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 886E361351 for ; Tue, 22 Jun 2021 14:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229988AbhFVO77 (ORCPT ); Tue, 22 Jun 2021 10:59:59 -0400 Received: from fllv0016.ext.ti.com ([198.47.19.142]:34164 "EHLO fllv0016.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230433AbhFVO77 (ORCPT ); Tue, 22 Jun 2021 10:59:59 -0400 Received: from fllv0035.itg.ti.com ([10.64.41.0]) by fllv0016.ext.ti.com (8.15.2/8.15.2) with ESMTP id 15MEvYkH122897; Tue, 22 Jun 2021 09:57:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ti.com; s=ti-com-17Q1; t=1624373854; bh=3RpZBa2MozVuA4vNzmdoop9q6l8luMuPvhHJNcpIVOY=; h=From:To:CC:Subject:Date; b=M2niN1GF2zQIWTBZxXyjNUUb6ARGuV0yritwGhbX9sr+JuDBUYQiUOdmr5DGjFkIC HAmn+Ew/3yG630nZZrl6/W8qgQDQ3TInLeshjpYt8iDK238y5YXXI7azKeevVT7Efs NL1pn9KjXu7wW+bOMMRf/n88uBBnkHLKFRM4i3f8= Received: from DLEE108.ent.ti.com (dlee108.ent.ti.com [157.170.170.38]) by fllv0035.itg.ti.com (8.15.2/8.15.2) with ESMTPS id 15MEvYDH022236 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=FAIL); Tue, 22 Jun 2021 09:57:34 -0500 Received: from DLEE107.ent.ti.com (157.170.170.37) by DLEE108.ent.ti.com (157.170.170.38) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Tue, 22 Jun 2021 09:57:34 -0500 Received: from fllv0040.itg.ti.com (10.64.41.20) by DLEE107.ent.ti.com (157.170.170.37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2 via Frontend Transport; Tue, 22 Jun 2021 09:57:34 -0500 Received: from ula0132425.ent.ti.com (ileax41-snat.itg.ti.com [10.172.224.153]) by fllv0040.itg.ti.com (8.15.2/8.15.2) with ESMTP id 15MEvVAd036396; Tue, 22 Jun 2021 09:57:31 -0500 From: Vignesh Raghavendra To: Greg Kroah-Hartman , Jiri Slaby CC: Vignesh Raghavendra , Tony Lindgren , , , Linux ARM Mailing List , Jan Kiszka Subject: [PATCH v2] serial: 8250: 8250_omap: Fix possible interrupt storm on K3 SoCs Date: Tue, 22 Jun 2021 20:27:04 +0530 Message-ID: <20210622145704.11168-1-vigneshr@ti.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 X-EXCLAIMER-MD-CONFIG: e1e8a2fd-e40a-4ac6-ac9b-f7e9cc9ee180 Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org On K3 family of SoCs (which includes AM654 SoC), it is observed that RX TIMEOUT is signalled after RX FIFO has been drained, in which case a dummy read of RX FIFO is required to clear RX TIMEOUT condition. Otherwise, this would lead to an interrupt storm. Fix this by introducing UART_RX_TIMEOUT_QUIRK flag and doing a dummy read in IRQ handler when RX TIMEOUT is reported with no data in RX FIFO. Fixes: be70874498f3 ("serial: 8250_omap: Add support for AM654 UART controller") Reported-by: Jan Kiszka Signed-off-by: Vignesh Raghavendra Tested-by: Jan Kiszka --- v2: Restrict workaround to K3 family of devices only (ti,am654-uart) where issue was reported. v1: https://lore.kernel.org/r/20210511151955.28071-1-vigneshr@ti.com drivers/tty/serial/8250/8250_omap.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_omap.c b/drivers/tty/serial/8250/8250_omap.c index c06631ced414..79418d4beb48 100644 --- a/drivers/tty/serial/8250/8250_omap.c +++ b/drivers/tty/serial/8250/8250_omap.c @@ -43,6 +43,7 @@ #define UART_ERRATA_CLOCK_DISABLE (1 << 3) #define UART_HAS_EFR2 BIT(4) #define UART_HAS_RHR_IT_DIS BIT(5) +#define UART_RX_TIMEOUT_QUIRK BIT(6) #define OMAP_UART_FCR_RX_TRIG 6 #define OMAP_UART_FCR_TX_TRIG 4 @@ -104,6 +105,9 @@ #define UART_OMAP_EFR2 0x23 #define UART_OMAP_EFR2_TIMEOUT_BEHAVE BIT(6) +/* RX FIFO occupancy indicator */ +#define UART_OMAP_RX_LVL 0x64 + struct omap8250_priv { int line; u8 habit; @@ -611,6 +615,7 @@ static int omap_8250_dma_handle_irq(struct uart_port *port); static irqreturn_t omap8250_irq(int irq, void *dev_id) { struct uart_port *port = dev_id; + struct omap8250_priv *priv = port->private_data; struct uart_8250_port *up = up_to_u8250p(port); unsigned int iir; int ret; @@ -625,6 +630,18 @@ static irqreturn_t omap8250_irq(int irq, void *dev_id) serial8250_rpm_get(up); iir = serial_port_in(port, UART_IIR); ret = serial8250_handle_irq(port, iir); + + /* + * On K3 SoCs, it is observed that RX TIMEOUT is signalled after + * FIFO has been drained, in which case a dummy read of RX FIFO + * is required to clear RX TIMEOUT condition. + */ + if (priv->habit & UART_RX_TIMEOUT_QUIRK && + (iir & UART_IIR_RX_TIMEOUT) == UART_IIR_RX_TIMEOUT && + serial_port_in(port, UART_OMAP_RX_LVL) == 0) { + serial_port_in(port, UART_RX); + } + serial8250_rpm_put(up); return IRQ_RETVAL(ret); @@ -1218,7 +1235,8 @@ static struct omap8250_dma_params am33xx_dma = { static struct omap8250_platdata am654_platdata = { .dma_params = &am654_dma, - .habit = UART_HAS_EFR2 | UART_HAS_RHR_IT_DIS, + .habit = UART_HAS_EFR2 | UART_HAS_RHR_IT_DIS | + UART_RX_TIMEOUT_QUIRK, }; static struct omap8250_platdata am33xx_platdata = {