From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: [PATCH 2/8] serial: tegra: Add delay after enabling FIFO mode Date: Tue, 5 May 2015 15:17:53 +0100 Message-ID: <1430835479-6613-3-git-send-email-jonathanh@nvidia.com> References: <1430835479-6613-1-git-send-email-jonathanh@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: In-Reply-To: <1430835479-6613-1-git-send-email-jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Laxman Dewangan , Greg Kroah-Hartman , Jiri Slaby Cc: linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Jon Hunter List-Id: linux-serial@vger.kernel.org For all tegra devices (up to t210), there is a hardware issue that requires software to wait for 3 UART clock periods after enabling the TX fifo, otherwise data could be lost. Signed-off-by: Jon Hunter --- drivers/tty/serial/serial-tegra.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c index 9e08d3f07509..0d9d7ceb1dbb 100644 --- a/drivers/tty/serial/serial-tegra.c +++ b/drivers/tty/serial/serial-tegra.c @@ -885,6 +885,16 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup) tup->fcr_shadow |= TEGRA_UART_TX_TRIG_16B; tegra_uart_write(tup, tup->fcr_shadow, UART_FCR); + /* Dummy read to ensure the write is posted */ + tegra_uart_read(tup, UART_SCR); + + /* + * For all tegra devices (up to t210), there is a hardware issue that + * requires software to wait for 3 UART clock periods after enabling + * the TX fifo, otherwise data could be lost. + */ + tegra_uart_wait_cycle_time(tup, 3); + /* * Initialize the UART with default configuration * (115200, N, 8, 1) so that the receive DMA buffer may be -- 1.9.1