| Message ID | 4910A519.3030701@unicontrol.de (mailing list archive) |
|---|---|
| State | Superseded, archived |
| Delegated to: | Grant Likely |
| Headers | show |
Hi René, On Tue, Nov 04, 2008 at 08:40:09PM +0100, René Bürgel wrote: > 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. I think we should CC linux-serial to get some opinions about this. At least, if it stays like this, it should be mentioned in the source. > > -- > 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 > > > 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. > + */ Here are lines >80 chars. Please let scripts/checkpatch.pl check this patch (--strict doesn't hurt). And please try also Documentation/CodingStyle.txt. It really helps maintaining that huge amount of code the kernel is. > + > +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); > + } > + } Function inside a function? Haven't seen this before in kernel code. I don't think it will be accepted, but leave this to maintainers. > + > + > + 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 No // comments please. > + 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); Bye, Wolfram
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);