From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.kernel.org ([198.145.29.99]:44442 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S967312AbeEXJvD (ORCPT ); Thu, 24 May 2018 05:51:03 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vignesh R , Sasha Levin Subject: [PATCH 4.9 93/96] serial: 8250: Dont service RX FIFO if interrupts are disabled Date: Thu, 24 May 2018 11:39:16 +0200 Message-Id: <20180524093611.223538320@linuxfoundation.org> In-Reply-To: <20180524093605.602125311@linuxfoundation.org> References: <20180524093605.602125311@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vignesh R [ Upstream commit 2e9fe539108320820016f78ca7704a7342788380 ] Currently, data in RX FIFO is read based on UART_LSR register state even if RDI and RLSI interrupts are disabled in UART_IER register. This is because when IRQ handler is called due to TX FIFO empty event, RX FIFO is serviced based on UART_LSR register status instead of UART_IIR status. This defeats the purpose of disabling UART RX FIFO interrupts during throttling(see, omap_8250_throttle()) as IRQ handler continues to drain UART RX FIFO resulting in overflow of buffer at tty layer. Fix this by making sure that driver drains UART RX FIFO only when UART_IIR_RDI is set along with UART_LSR_BI or UART_LSR_DR bits. Signed-off-by: Vignesh R Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -1815,7 +1815,8 @@ int serial8250_handle_irq(struct uart_po status = serial_port_in(port, UART_LSR); - if (status & (UART_LSR_DR | UART_LSR_BI)) { + if (status & (UART_LSR_DR | UART_LSR_BI) && + iir & UART_IIR_RDI) { if (!up->dma || handle_rx_dma(up, iir)) status = serial8250_rx_chars(up, status); }