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.
2. Fix for Busy Detect on LCR write: The DesignWare APB UART has a feature which causes a new Busy Detect interrupt to be generated if it's busy when the LCR is written. This fix saves the value of the LCR and rewrites it after clearing the interrupt.
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.
Signed-off-by: Marc St-Jean <[EMAIL PROTECTED]>
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).
@@ -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(struadd_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.
WBR, Sergei - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
