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
quoted hunk
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.
quoted hunk
+
+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.
quoted hunk
+
+
+ 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.
quoted hunk
+ 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);
20 more quoted lines
Bye,
Wolfram
--
Dipl.-Ing. Wolfram Sang | http://www.pengutronix.de
Pengutronix - Linux Solutions for Science and Industry