From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752016AbdEBHqO (ORCPT ); Tue, 2 May 2017 03:46:14 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:33397 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751781AbdEBHqK (ORCPT ); Tue, 2 May 2017 03:46:10 -0400 From: Joel Stanley To: Greg Kroah-Hartman , Jiri Slaby Cc: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Andy Shevchenko , Benjamin Herrenschmidt , Jeremy Kerr , Mark Rutland , Rob Herring , openbmc@lists.ozlabs.org Subject: [PATCH v4 1/2] serial: 8250: Add flag so drivers can avoid THRE probe Date: Tue, 2 May 2017 17:15:42 +0930 Message-Id: <20170502074543.1380-2-joel@jms.id.au> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170502074543.1380-1-joel@jms.id.au> References: <20170502074543.1380-1-joel@jms.id.au> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The probing of THRE irq behaviour assumes the other end will be reading bytes out of the buffer in order to probe the port at driver init. In some cases the other end cannot be relied upon to read these bytes, so provide a flag for them to skip this step. Bit 19 was chosen as the flags are a int and the top bits are taken. Acked-by: Benjamin Herrenschmidt Signed-off-by: Joel Stanley --- v3: - No change v3: - Correct the bit number in the changelog v2: - No change Signed-off-by: Joel Stanley --- drivers/tty/serial/8250/8250_port.c | 2 +- include/linux/serial_core.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 6119516ef5fc..60a6c247340f 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2229,7 +2229,7 @@ int serial8250_do_startup(struct uart_port *port) } } - if (port->irq) { + if (port->irq && !(up->port.flags & UPF_NO_THRE_TEST)) { unsigned char iir1; /* * Test for UARTs that do not reassert THRE when the diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 58484fb35cc8..260245deec94 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -195,6 +195,7 @@ struct uart_port { #define UPF_NO_TXEN_TEST ((__force upf_t) (1 << 15)) #define UPF_MAGIC_MULTIPLIER ((__force upf_t) ASYNC_MAGIC_MULTIPLIER /* 16 */ ) +#define UPF_NO_THRE_TEST ((__force upf_t) (1 << 19)) /* Port has hardware-assisted h/w flow control */ #define UPF_AUTO_CTS ((__force upf_t) (1 << 20)) #define UPF_AUTO_RTS ((__force upf_t) (1 << 21)) -- 2.11.0