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Date: Thu, 25 Jan 2007 17:50:34 +0300
From: Sergei Shtylyov <sshtylyov@...mvista.com>
To: Marc St-Jean <Marc_St-Jean@...-sierra.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 master
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... :-/
> {
> + /* Save the offset before it's remapped */
> + int save_offset = offset;
Is there real need to save this? What regshift equals for this UART?
> 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...
> + in_irq())
I'd suggest to either indent this line right (start below 2ns paren of if
stmt) or keep on the 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?
> @@ -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. :-)
> 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
> 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... :-)
> 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.
WBR, Sergei
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