Re: [PATCH] serial driver PMC MSP71xx, kernel linux-mips.git mast er
- From: Marc St-Jean <Marc_St-Jean@xxxxxxxxxxxxxx>
- Date: Fri, 16 Feb 2007 09:06:47 -0800
Sergei Shtylyov wrote:
Hello.
Marc St-Jean wrote:
> There are three different fixes:
> 1. Fix for DesignWare APB THRE errata:
> 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.
> It appears that the "8250-uart-backup-timer.patch" in the "mm" tree also
> fixes it so we have dropped our initial workaround.
> This patch now needs to be applied on top of that "mm" patch.
This patch has hit the mainline kernel already.
I see, I'll drop the reference to the "mm" patch.
> 3. Workaround for interrupt/data concurrency issue:
> The SoC needs to ensure that writes that can cause interrupts to be
> cleared reach the UART before returning from the ISR. This fix reads
> a non-destructive register on the UART so the read transaction
> completion ensures the previously queued write transaction has
> also completed.
> The differences from the last attempt is dropping the call to
> in_irq() and including more detailed description of the fixes.
The difference part would better be under the "---" cutoff line, along
with diffstat.
This way it gets auto-removed by quilt/git when applying the patch.
I'll add to the next posting.
> diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
> index 3d91bfc..bfaacc5 100644
> --- a/drivers/serial/8250.c
> +++ b/drivers/serial/8250.c
> @@ -308,6 +308,7 @@ static unsigned int serial_in(struct uar
> return inb(up->port.iobase + 1);
>
> case UPIO_MEM:
> + case UPIO_DWAPB:
> return readb(up->port.membase + offset);
>
> case UPIO_MEM32:
> @@ -333,6 +334,8 @@ #endif
> static void
> serial_out(struct uart_8250_port *up, int offset, int value)
> {
> + /* Save the offset before it's remapped */
> + int save_offset = offset;
> offset = map_8250_out_reg(up, offset) << up->port.regshift;
>
> switch (up->port.iotype) {
I've just got an idea how to "beautify" this code -- rename the
'offset'
arg to something like reg, and then declare/init 'offset' as local
variable.
Would certainly look better (and worth doing in all serial_* accessros).
I agree but am having enough of a hard time getting the bare minimum
accepted that I don't dare touch any unnecessary lines.
> @@ -359,6 +362,18 @@ #endif
> 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)
> + value = serial_in(up, UART_IER);
> + break;
> +
> default:
> outb(value, up->port.iobase + offset);
> }
> @@ -2454,8 +2485,8 @@ int __init serial8250_start_console(stru
>
> 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 :
> + line, port->iotype >= UPIO_MEM ? "MMIO" : "I/O port",
> + port->iotype >= UPIO_MEM ? (unsigned long) port->mapbase :
> (unsigned long) port->iobase, options);
> if (!(serial8250_console.flags & CON_ENABLED)) {
> serial8250_console.flags &= ~CON_PRINTBUFFER;
I've remembered why I decided not to fix it: this code only gets called
from 8250__eraly.c which can't handle anything beyond UPIO_MEM anyway.
We don't use 8250_early and I've tested it works without, so I'll drop this
change.
Thanks,
Marc
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