From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Welling Subject: Re: [PATCH] serial: 8250: Do XR17V35X specific wakeup in serial8250_do_startup Date: Fri, 19 Jun 2015 12:09:10 -0500 Message-ID: <20150619170910.GA6002@deathray> References: <1434726737-2585-1-git-send-email-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1434726737-2585-1-git-send-email-joro@8bytes.org> Sender: linux-kernel-owner@vger.kernel.org To: Joerg Roedel Cc: Greg Kroah-Hartman , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Joerg Roedel , Peter Hurley , Joe Schultz List-Id: linux-serial@vger.kernel.org On Fri, Jun 19, 2015 at 05:12:17PM +0200, Joerg Roedel wrote: > From: Joerg Roedel > > While debugging why my 8-port XR17V35X card does not work > with the in-kernel serial driver, I found that some chip > specific wakeup code is necessary to get it working. > > Specificly the EFR_ECB bit needs to be set in the > chip-specific UART_XR_EFR register, so that writing to a > couple of other configuration bits is enabled. > > Cc: Peter Hurley > Cc: Michael Welling > Cc: Joe Schultz > Signed-off-by: Joerg Roedel > --- > drivers/tty/serial/8250/8250_core.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c > index 4506e40..de34db3 100644 > --- a/drivers/tty/serial/8250/8250_core.c > +++ b/drivers/tty/serial/8250/8250_core.c > @@ -2176,6 +2176,18 @@ int serial8250_do_startup(struct uart_port *port) > */ > enable_rsa(up); > #endif > + > + /* > + * Do this right before clearing the FIFOs to prevent > + * interrupt storm. > + */ > + if (port->type == PORT_XR17V35X) { > + /* Wake up and initialize UART */ > + serial_port_out(port, UART_XR_EFR, UART_EFR_ECB); > + serial_port_out(port, UART_IER, 0); > + serial_port_out(port, UART_LCR, 0); > + } > + Looks good to me. The datasheet indicates that bit 4 of the EFR needs to be set to access to IER [7:5], ISR [5:4], FCR[5:4], MCR[7:5], MSR. > /* > * Clear the FIFO buffers and disable them. > * (they will be reenabled in set_termios()) > -- > 1.8.4.5 >