> Here is my second attempt at the serial driver patch for the
> PMC-Sierra MSP71xx device.
> There are three different fixes:
> 1. Fix for THRE errata
> - I verified the UART_BUG_TXEN fix does not help with this erratum.
> - I left our current fix in until I get our platform booting on
> 2.6.20-rc4 to try the mm tree "8250-uart-backup-timer.patch".
> Feel free to ignore for now.
> 2. Fix for Busy Detect on LCR write
> - Moved to new UPIO_DWAPB iotype. Because the new type is a memory
> mapped device and there are several tests for UPIO_MEM, this involved
> updating serial_core.c and 8250_early.c in addition to 8250.c.
> - I tried implementing this totally in serial_in as suggested, but
> it can't be done because of bit overlap between UART_IIR_NO_INT and
> UART_IIR_BUSY. Also there is no way to set the interrupt "handled = 1"
> from serial_in.
> 3. Workaround for interrupt/data concurrency issue
> - Moved to new UPIO_DWAPB iotype.
> Index: linux_2_6/drivers/serial/8250.c
> ===================================================================
> RCS file: linux_2_6/drivers/serial/8250.c,v
> retrieving revision 1.1.1.7
> diff -u -r1.1.1.7 8250.c
> --- linux_2_6/drivers/serial/8250.c 19 Oct 2006 21:00:58 -0000 1.1.1.7
> +++ linux_2_6/drivers/serial/8250.c 24 Jan 2007 23:55:27 -0000
[...]
> @@ -333,6 +334,8 @@
> static void
> serial_out(struct uart_8250_port *up, int offset, int value)
Your patch is clearly garbled again, something added an extra space to all
lines stating with space... :-/
I see that but was under the impression cvs diff did that so all lines
lineup correctly whether they have a +, -, or neither.
It doesn't affect applying the patches for me, did you try?
> {
> + /* Save the offset before it's remapped */
> + int save_offset = offset;
Is there real need to save this? What regshift equals for this UART?
Yes, we have a regshift of 2 on this SoC and it could be different on other
SoCs which reuse the UART IP.
> offset = map_8250_out_reg(up, offset) << up->port.regshift;
> switch (up->port.iotype) {
> @@ -359,6 +362,19 @@
> writeb(value, up->port.membase + offset);
> break;
>
> + case UPIO_DWAPB:
> + /* Save the LCR value so it can be re-written when a
> + * Busy Detect interrupt occurs. */
> + if (save_offset == UART_LCR)
> + up->lcr = value;
> + writeb(value, up->port.membase + offset);
> + /* Read the IER to ensure any interrupt is cleared before
> + * returning from ISR. */
> + if ((save_offset == UART_TX || save_offset == UART_IER) &&
Not sure how an IER read ensures that...
It's just a dummy read to ensure that any writes which clear interrupts have
reached the device before returning from the IRQ.
> Index: linux_2_6/drivers/serial/8250_early.c
> ===================================================================
> RCS file: linux_2_6/drivers/serial/8250_early.c,v
> retrieving revision 1.1.1.3
> diff -u -r1.1.1.3 8250_early.c
> --- linux_2_6/drivers/serial/8250_early.c 19 Oct 2006 20:08:20 -0000 1.1.1.3
> +++ linux_2_6/drivers/serial/8250_early.c 24 Jan 2007 23:55:27 -0000
> @@ -46,7 +46,7 @@
>
> static unsigned int __init serial_in(struct uart_port *port, int offset)
> {
> - if (port->iotype == UPIO_MEM)
> + if (port->iotype == UPIO_MEM || port->iotype == UPIO_DWAPB)
> return readb(port->membase + offset);
> else
> return inb(port->iobase + offset);
> @@ -54,7 +54,7 @@
>
> static void __init serial_out(struct uart_port *port, int offset, int value)
> {
> - if (port->iotype == UPIO_MEM)
> + if (port->iotype == UPIO_MEM || port->iotype == UPIO_DWAPB)
> writeb(value, port->membase + offset);
> else
> outb(value, port->iobase + offset);
> @@ -233,7 +233,7 @@
> return 0;
>
> /* Try to start the normal driver on a matching line. */
> - mmio = (port->iotype == UPIO_MEM);
> + mmio = (port->iotype == UPIO_MEM || port->iotype == UPIO_DWAPB);
> line = serial8250_start_console(port, device->options);
> if (line < 0)
> printk("No ttyS device at %s 0x%lx for console\n",
From your 8250_eraly.c changes I can conclude regshift == 1 (it doesn't
currently support other cases). So, serial_pot() doesn't need save_offset. :-)
Our regshift is definitely 2 on this SoC and we don't have any problems with
console output before the serial driver opens. So assuming it's using
8250_early.c for initial console output I can only conclude that it works
because UART_TX is offset 0 and the port was left configured from our
ROM monitor.
> Index: linux_2_6/include/linux/serial_reg.h
> ===================================================================
> RCS file: linux_2_6/include/linux/serial_reg.h,v
> retrieving revision 1.1.1.2
> diff -u -r1.1.1.2 serial_reg.h
> --- linux_2_6/include/linux/serial_reg.h 19 Oct 2006 18:29:50 -0000 1.1.1.2
> +++ linux_2_6/include/linux/serial_reg.h 24 Jan 2007 23:55:29 -0000
> @@ -218,6 +218,10 @@
> #define UART_FCR_PXAR16 0x80 /* receive FIFO treshold = 16 */
> #define UART_FCR_PXAR32 0xc0 /* receive FIFO treshold = 32 */
>
> +/*
> + * DesignWare APB UART
> + */
> +#define UART_IIR_BUSY 0x07 /* Busy Detect */
I'd suggest keeping this with other UART_IIR_* #defines, separated by the
more elaborate comment.
Will do. I noticed that the other non-standard value UART_IIR_TOD 0x08 is with
the Xscale stuff so I followed suit.
Marc