From patchwork Mon Sep 24 06:19:03 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Powerpc 8xx CPM_UART too many interrupts X-Patchwork-Submitter: Christophe LEROY X-Patchwork-Id: 186298 Message-Id: <201209240619.q8O6J3Ft029443@localhost.localdomain> To: Alan Cox , Vitaly Bordug , Marcelo Tosatti Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org Date: Mon, 24 Sep 2012 08:19:03 +0200 From: Christophe Leroy List-Id: Linux on PowerPC Developers Mail List Setting the fifo to only 1 byte generates one interrupt every 1ms at 9600 bauds. This is too much. This patch reduces the threshold to speeds below 2400 bauds like in the 8250 UART driver. Signed-off-by: Christophe Leroy --- linux-3.5-vanilla/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-07-21 22:58:29.000000000 +0200 +++ linux-3.5/drivers/tty/serial/cpm_uart/cpm_uart_core.c 2012-08-09 17:38:37.000000000 +0200 @@ -71,7 +71,7 @@ /**************************************************************/ -#define HW_BUF_SPD_THRESHOLD 9600 +#define HW_BUF_SPD_THRESHOLD 2400 /* * Check, if transmit buffers are processed @@ -505,7 +505,7 @@ pr_debug("CPM uart[%d]:set_termios\n", port->line); baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16); - if (baud <= HW_BUF_SPD_THRESHOLD || + if (baud < HW_BUF_SPD_THRESHOLD || (pinfo->port.state && pinfo->port.state->port.tty->low_latency)) pinfo->rx_fifosize = 1; else