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Date: Thu, 25 Jan 2007 15:10:17 -0800
From: Marc St-Jean <Marc_St-Jean@...-sierra.com>
To: Sergei Shtylyov <sshtylyov@...mvista.com>
Cc: linux-mips@...ux-mips.org, linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial driver PMC MSP71xx, kernel linux-mips.git mast
er
Sergei Shtylyov wrote:
> Marc St-Jean wrote:
> > 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.
> > + in_irq())
>
> I'd suggest to either indent this line right (start below 2ns paren
> of if
> stmt) or keep on the same line.
OK, moved onto same line.
> > + value = serial_in(up, UART_IER);
> > + break;
> > +
> > default:
> > outb(value, up->port.iobase + offset);
> > }
> > @@ -1016,6 +1032,17 @@
> > up->bugs |= UART_BUG_NOMSR;
> > #endif
> >
> > + /* Workaround:
> > + * The DesignWare SoC UART part has a bug for all
> > + * versions before 3.03a (2005-07-18)
> > + * In brief, this is a non-standard 16550 in that the THRE
> interrupt
> > + * will not re-assert itself simply by disabling and
> re-enabling the
> > + * THRI bit in the IER, it is only re-enabled if a character is
> actually
> > + * sent out.
> > + */
> > + if( up->port.flags & UPF_DW_THRE_BUG )
> > + up->bugs |= UART_BUG_DWTHRE;
> > +
> > serial_outp(up, UART_LCR, save_lcr);
> >
> > if (up->capabilities != uart_config[up->port.type].flags) {
> > @@ -1141,6 +1168,12 @@
> > iir = serial_in(up, UART_IIR);
> > if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)
> > transmit_chars(up);
> > + } else if (up->bugs & UART_BUG_DWTHRE) {
> > + unsigned char lsr, iir;
> > + lsr = serial_in(up, UART_LSR);
> > + iir = serial_in(up, UART_IIR);
> > + if (lsr & UART_LSR_THRE)
>
> Why read IIR if you don't check it?
Good point. I didn't write that one and assumed reading the IIR was part of the fix.
It just tested fine without it so it's gone.
> > @@ -2352,9 +2402,12 @@
> >
> > add_preferred_console("ttyS", line, options);
> > printk("Adding console on ttyS%d at %s 0x%lx (options '%s')\n",
> > - line, port->iotype == UPIO_MEM ? "MMIO" : "I/O port",
> > - port->iotype == UPIO_MEM ? (unsigned long) port->mapbase :
> > - (unsigned long) port->iobase, options);
> > + line,
> > + (port->iotype == UPIO_MEM || port->iotype == UPIO_DWAPB)
> > + ? "MMIO" : "I/O port",
> > + (port->iotype == UPIO_MEM || port->iotype == UPIO_DWAPB)
> > + ? (unsigned long) port->mapbase : (unsigned
> long) port->iobase,
> > + options);
> > if (!(serial8250_console.flags & CON_ENABLED)) {
> > serial8250_console.flags &= ~CON_PRINTBUFFER;
> > register_console(&serial8250_console);
> [...]
> > 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/drivers/serial/serial_core.c
> > ===================================================================
> > RCS file: linux_2_6/drivers/serial/serial_core.c,v
> > retrieving revision 1.1.1.7
> > diff -u -r1.1.1.7 serial_core.c
> > --- linux_2_6/drivers/serial/serial_core.c 19 Oct 2006 21:00:58
> -0000 1.1.1.7
> > +++ linux_2_6/drivers/serial/serial_core.c 24 Jan 2007 23:55:28 -0000
> > @@ -1669,9 +1669,10 @@
> >
> > ret = sprintf(buf, "%d: uart:%s %s%08lX irq:%d",
> > port->line, uart_type(port),
> > - port->iotype == UPIO_MEM ? "mmio:0x" : "port:",
> > - port->iotype == UPIO_MEM ? port->mapbase :
> > - (unsigned long)
> port->iobase,
> > + (port->iotype == UPIO_MEM || port->iotype ==
> UPIO_DWAPB)
> > + ? "mmio:0x" : "port:",
> > + (port->iotype == UPIO_MEM || port->iotype ==
> UPIO_DWAPB)
> > + ? port->mapbase : (unsigned long)
> port->iobase,
> > port->irq);
> > if (port->type == PORT_UNKNOWN) {
>
> Needless change. My patch that fixes this function is in Linus' tree
> since
> September, not sure why you don't have it:
>
> http://www2.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=6c6a2334a1e8af7c3eaab992732825fa9ade77cf
I have it, I forgot to respin against the master.
>
> > Index: linux_2_6/include/linux/serial_core.h
> > ===================================================================
> > RCS file: linux_2_6/include/linux/serial_core.h,v
> > retrieving revision 1.1.1.7
> > diff -u -r1.1.1.7 serial_core.h
> > --- linux_2_6/include/linux/serial_core.h 19 Oct 2006 21:01:02
> -0000 1.1.1.7
> > +++ linux_2_6/include/linux/serial_core.h 24 Jan 2007 23:55:28 -0000
> [...]
> > @@ -274,6 +277,7 @@
> > struct device *dev; /* parent
> device */
> > unsigned char hub6; /* this should
> be in the 8250 driver */
> > unsigned char unused[3];
> > + void *user; /*
> generic platform 'user' pointer */
>
> Erm, 'private' or 'data' would've sounded better in the kernel context,
> IMHO... :-)
OK, I picked 'data'.
> > 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
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