From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mo-p00-ob.rzone.de (mo-p00-ob.rzone.de [81.169.146.161]) by ozlabs.org (Postfix) with ESMTP id 09E47DDE17 for ; Wed, 5 Nov 2008 06:40:19 +1100 (EST) Message-ID: <4910A519.3030701@unicontrol.de> Date: Tue, 04 Nov 2008 20:40:09 +0100 From: =?ISO-8859-15?Q?Ren=E9_B=FCrgel?= MIME-Version: 1.0 To: Wolfram Sang , linuxppc-dev@ozlabs.org Subject: Re: [PATCH V3] workaround for mpc52xx erratum #364 (serial may not be reset in break state) References: <490F51E7.3020309@unicontrol.de> <4910274E.5030305@unicontrol.de> <20081104111545.GB17864@pengutronix.de> In-Reply-To: <20081104111545.GB17864@pengutronix.de> Content-Type: multipart/mixed; boundary="------------020606040600000400020507" 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. --------------020606040600000400020507 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 8bit Hey, folks This is v3 of my patch to work around erratum #364 of the MPC5200(B). I removed most "magic" looking numbers, documenting the rest. As mentioned before, the previous patches weren't working for low baudrates (<9600). This should be fixed now. But there's still one thing, that bothers me a bit - if there is REALLY a break on the line, closing the driver may take until it's gone. I don't know whether this is really satisfying, but i think it's better than the alternative: no serial connection until the next reboot. -- 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 --------------020606040600000400020507 Content-Type: text/plain; name="130-mpc52xx_erratum_364.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename="130-mpc52xx_erratum_364.patch" diff --git a/drivers/serial/mpc52xx_uart.c b/drivers/serial/mpc52xx_uart.c index 6117d3d..a2bb4d9 100644 --- a/drivers/serial/mpc52xx_uart.c +++ b/drivers/serial/mpc52xx_uart.c @@ -496,6 +496,59 @@ mpc52xx_uart_break_ctl(struct uart_port *port, int ctl) spin_unlock_irqrestore(&port->lock, flags); } +/* + * This is a workaround for processor bug #364 described in MPC5200 (L25R) Errata. + * The bug is still present in MPC5200B, but currently not listed in its errata sheet + * + * The workaround resets the baudrate to the slowest possible, + * waits for a stable state and resets break state repeatedly if necessary. + * Optionally it can release the lock while waiting. + * + * That baudrate is roughly port->uartclk / (1000 * 1000) + * The minimum wait time for the first try has to include the time to wait for stop-bits and a character, + * we wait for 2 chars to be sure + * Consecutive waits must just receive one character. + */ + +static void mpc52xx_uart_reset_rx(struct uart_port *port, bool unlock, unsigned long flags) +{ +#ifdef CONFIG_PPC_MPC52xx + void reset_errors_and_wait(struct uart_port *port, bool unlock, unsigned long flags, unsigned int delay) + { + struct mpc52xx_psc __iomem *psc = PSC(port); + out_8(&psc->command,MPC52xx_PSC_RST_ERR_STAT); + if (unlock) { + disable_irq(port->irq); + spin_unlock_irqrestore(&port->lock, flags); + } + mdelay( delay ); + if (unlock) { + spin_lock_irqsave(&port->lock, flags); + enable_irq(port->irq); + } + } + + + struct mpc52xx_psc __iomem *psc = PSC(port); + + // One character on the serial port may consist of up to 12 bits. + // So the time to receive one char is 12 /*bits*/ / (port->uartclk / (1000 * 1000) /*MHz -> Hz*/) * 1000 /*s -> ms*/, + // but we'll wait 50% longer just to make sure + unsigned int one_char_receive_duration = (12 * 1000) / (port->uartclk / (1000 * 1000) ); + + /* CT=0xFFFF sets the serial line to the minimal possible baudrate depending on the uartclk. */ + out_8(&psc->ctur, 0xFF); + out_8(&psc->ctlr, 0xFF); + + reset_errors_and_wait( port, unlock, flags, one_char_receive_duration * 2 ); + + while ((in_be16(&psc->mpc52xx_psc_status)) & MPC52xx_PSC_SR_RB) { + reset_errors_and_wait( port, unlock, flags, one_char_receive_duration ); + } +#endif + out_8(&psc->command,MPC52xx_PSC_RST_RX); +} + static int mpc52xx_uart_startup(struct uart_port *port) { @@ -510,7 +563,7 @@ 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(port, false, 0); out_8(&psc->command, MPC52xx_PSC_RST_TX); out_be32(&psc->sicr, 0); /* UART mode DCD ignored */ @@ -529,7 +582,7 @@ 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(port, false, 0); if (!uart_console(port)) out_8(&psc->command, MPC52xx_PSC_RST_TX); @@ -588,9 +641,6 @@ 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 +657,12 @@ 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(port, true, flags); 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); --------------020606040600000400020507--