From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p00-ob.rzone.de (mo-p00-ob.rzone.de [81.169.146.160]) by ozlabs.org (Postfix) with ESMTP id 6D6E5DDEDE for ; Tue, 4 Nov 2008 06:32:14 +1100 (EST) Message-ID: <490F51E7.3020309@unicontrol.de> Date: Mon, 03 Nov 2008 20:32:55 +0100 From: =?ISO-8859-15?Q?Ren=E9_B=FCrgel?= MIME-Version: 1.0 To: linuxppc-dev@ozlabs.org Subject: [PATCH] workaround for mpc52xx erratum #364 (serial may not be reset in break state) Content-Type: multipart/mixed; boundary="------------010301060909020608050500" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , This is a multi-part message in MIME format. --------------010301060909020608050500 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Hi This patch is a workaround for bug #364 found in the MPC52xx processor. The errata document can be found under http://www.freescale.com/files/32bit/doc/errata/MPC5200E.pdf?fpsp=1&WT_TYPE=Errata&WT_VENDOR=FREESCALE&WT_FILE_FORMAT=pdf&WT_ASSET=Documentation When a device with a low baudrate is connected to the serial port, but the processor "listens" on a higher baudrate, it might falsely receive breaks from the controller. During a break, the serial controller may not be reset. The appended patch provides a workaround for that situation by lowering the baudrate without resetting the controller and waiting until no break is received anymore. -- René Bürgel Software Engineer Unicontrol Systemtechnik GmbH OT Dittersbach Sachsenburger Weg 34 09669 Frankenberg Tel.: 03 72 06/ 88 73 - 19 Fax: 03 72 06/ 88 73 - 60 E-Mail: r.buergel@unicontrol.de Internet: www.unicontrol.de Unicontrol Systemtechnik GmbH Geschäftsführer: Dipl.-Ing. Siegfried Heinze Sitz der Gesellschaft: Frankenberg Registergericht: Amtsgericht Chemnitz, HRB 15 475 --------------010301060909020608050500 Content-Type: text/plain; name="122-mpc52xx_erratum_364.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="122-mpc52xx_erratum_364.patch" diff --git a/drivers/serial/mpc52xx_uart.c b/drivers/serial/mpc52xx_uart.c index 6117d3d..929524b 100644 --- a/drivers/serial/mpc52xx_uart.c +++ b/drivers/serial/mpc52xx_uart.c @@ -496,6 +496,27 @@ mpc52xx_uart_break_ctl(struct uart_port *port, int ctl) spin_unlock_irqrestore(&port->lock, flags); } +/* macro with helper macros to safely reset rx which mustn't be done in break state. + * This is a workaround for processor bug #364 described in MPC5200 (L25R) Errata. + * + * The workaround resets the baudrate to 4800, waits for a stable state and resets break state repeatedly if necessary + * optionally it can release the lock while waiting. + * 1 character at 4800 baud takes 2ms, 3ms should be enough for 1 character at higher speed and 1 char at lowest + * works only with longer delays + */ +#define LOCK(code) code +#define DONT_LOCK(code) +#define mpc52xx_uart_reset_rx(LOCK) \ + out_8(&psc->ctur,0x01); \ + out_8(&psc->ctlr,0xae); \ + do { \ + out_8(&psc->command,MPC52xx_PSC_RST_ERR_STAT); \ + LOCK(disable_irq(port->irq); spin_unlock_irqrestore(&port->lock, flags)); \ + mdelay(10); \ + LOCK(spin_lock_irqsave(&port->lock, flags); enable_irq(port->irq)); \ + } while ((in_be16(&psc->mpc52xx_psc_status)) & MPC52xx_PSC_SR_RB); \ + out_8(&psc->command,MPC52xx_PSC_RST_RX); + static int mpc52xx_uart_startup(struct uart_port *port) { @@ -510,7 +531,7 @@ mpc52xx_uart_startup(struct uart_port *port) return ret; /* Reset/activate the port, clear and enable interrupts */ - out_8(&psc->command, MPC52xx_PSC_RST_RX); + mpc52xx_uart_reset_rx(DONT_LOCK); out_8(&psc->command, MPC52xx_PSC_RST_TX); out_be32(&psc->sicr, 0); /* UART mode DCD ignored */ @@ -529,7 +550,7 @@ mpc52xx_uart_shutdown(struct uart_port *port) struct mpc52xx_psc __iomem *psc = PSC(port); /* Shut down the port. Leave TX active if on a console port */ - out_8(&psc->command, MPC52xx_PSC_RST_RX); + mpc52xx_uart_reset_rx(DONT_LOCK); if (!uart_console(port)) out_8(&psc->command, MPC52xx_PSC_RST_TX); @@ -588,9 +609,6 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct ktermios *new, /* Get the lock */ spin_lock_irqsave(&port->lock, flags); - /* Update the per-port timeout */ - uart_update_timeout(port, new->c_cflag, baud); - /* Do our best to flush TX & RX, so we don't loose anything */ /* But we don't wait indefinitly ! */ j = 5000000; /* Maximum wait */ @@ -607,9 +625,12 @@ mpc52xx_uart_set_termios(struct uart_port *port, struct ktermios *new, "Some chars may have been lost.\n"); /* Reset the TX & RX */ - out_8(&psc->command, MPC52xx_PSC_RST_RX); + mpc52xx_uart_reset_rx(LOCK); out_8(&psc->command, MPC52xx_PSC_RST_TX); + /* Update the per-port timeout */ + uart_update_timeout(port, new->c_cflag, baud); + /* Send new mode settings */ out_8(&psc->command, MPC52xx_PSC_SEL_MODE_REG_1); out_8(&psc->mode, mr1); --------------010301060909020608050500--