From patchwork Tue Jul 12 13:15:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: VAMSHI GAJJELA X-Patchwork-Id: 590004 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 596C7C43334 for ; Tue, 12 Jul 2022 13:15:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231249AbiGLNPf (ORCPT ); Tue, 12 Jul 2022 09:15:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229617AbiGLNPe (ORCPT ); Tue, 12 Jul 2022 09:15:34 -0400 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CE24E5C959 for ; Tue, 12 Jul 2022 06:15:30 -0700 (PDT) Received: by mail-pl1-x649.google.com with SMTP id k18-20020a170902c41200b0016c40543af4so4192925plk.0 for ; Tue, 12 Jul 2022 06:15:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=Jj15qoURj3emWvHLxBH2nPwiIzzLvd3mSNd7M20V7kc=; b=VrvPmlW1Mw9Qie6nuTLyJIEdvtB1q9qnbj5yZHc5WAz2gmilCGbHrAqHW+nbHnr1Yt QYCVTeIud8NWMDpleRg/psfMwA6QarcShJmRgGOPwCri+9+7X2GBA4+Tj+c4G58JlOR2 AAnOp9AzxbNQ7LsrvFRsrxgHUqqbYI38rxnkXJYQf4VtAcxDHSqE1u2CVWElkavoprVq MLPLZF4KKZ2n+NFw/z5bjZirvOBQtqzV8bEJ7ZcxpbnMBWkTdx+DSdszCF38jbVzKw1N v+nA8OfSDnRpifHP6YFfv5eLm0pP+A8Sl89jwczzX/VKEppia8uaYMmSmotBlTP99use TmPA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=Jj15qoURj3emWvHLxBH2nPwiIzzLvd3mSNd7M20V7kc=; b=uiQgMj3Vc8djiE/exqNCEB4OWw1KQyH0zUYxM0zjCmV1YSMlYd7b7xizSv+xDQYrLT h+QRbYaboh87nB0KRaFQ4rgGvGKC9+wyI9Uaq+d3Pgcew/ud+QZ87V9Q1VuMYu+G6YAz EfX8SSCAh5hG1mIr53YCcYl+G8zETeq9hMeLgldR3vo7znwNepLQ/42Ir5221wH2VYiA H09e2bWvx/ya1RukHgUwpwn4zzJFg6XPx2dXwWC4biXs1OFKRFAIvnEbsWu+0369YVKw 6AaSE+++lbtKUtU9fDqDl9oO9aruKkaXUWT0dRh9mGWsDD+r/t/39ytJA+x1RDf/zvoF 2Aeg== X-Gm-Message-State: AJIora90gvpDZH6V/GFL+3qEymEE/tlZHftGogHg88sFnYnelN8NmoHs ISqFxDH5cYw2o8OQfaOi1vnQVwYvhVJ8S+JYin04 X-Google-Smtp-Source: AGRyM1tiLhmBsSG07iMVccKmTqJMgw+sCcWHJFKw/dCojeh685N00bAiC1pMr5tl2AGmpOHdStzVwHzb7OqZJcAwSsTV X-Received: from vamshig51.c.googlers.com ([fda3:e722:ac3:cc00:3:22c1:c0a8:70c]) (user=vamshigajjela job=sendgmr) by 2002:a17:90b:247:b0:1f0:1192:7c22 with SMTP id fz7-20020a17090b024700b001f011927c22mr4471560pjb.232.1657631730301; Tue, 12 Jul 2022 06:15:30 -0700 (PDT) Date: Tue, 12 Jul 2022 18:45:23 +0530 Message-Id: <20220712131523.1874428-1-vamshigajjela@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.37.0.144.g8ac04bfd2-goog Subject: [PATCH] serial: 8250_dw: Avoid pslverr on reading empty receiver fifo From: Vamshi Gajjela To: Andy Shevchenko , Greg Kroah-Hartman , Jiri Slaby Cc: Miquel Raynal , Phil Edworthy , Emil Renner Berthing , Heikki Krogerus , Johan Hovold , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, VAMSHI GAJJELA Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org From: VAMSHI GAJJELA With PSLVERR_RESP_EN parameter set to 1, device generates an error response when an attempt to read empty RBR with FIFO enabled. This happens when LCR writes are ignored when UART is busy. dw8250_check_lcr() in retries to updateLCR, invokes dw8250_force_idle() to clear and reset fifo and eventually reads UART_RX causing pslverr. Avoid this by not reading RBR/UART_RX when no data is available. Signed-off-by: VAMSHI GAJJELA --- drivers/tty/serial/8250/8250_dw.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index f57bbd32ef11..a83222839884 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -81,9 +81,19 @@ static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value) static void dw8250_force_idle(struct uart_port *p) { + unsigned int lsr; struct uart_8250_port *up = up_to_u8250p(p); serial8250_clear_and_reinit_fifos(up); + + /* + * With PSLVERR_RESP_EN parameter set to 1, device generates pslverr + * error response when an attempt to read empty RBR with FIFO enabled + */ + lsr = p->serial_in(p, UART_LSR); + if ((up->fcr & UART_FCR_ENABLE_FIFO) && !(lsr & UART_LSR_DR)) + return; + (void)p->serial_in(p, UART_RX); }