Seventh attempt at the serial driver patch for the PMC-Sierra
MSP71xx devices.
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.
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.
Thanks,
Marc
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) {
@@ -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);
}
@@ -373,6 +388,7 @@ serial_out_sync(struct uart_8250_port *u
#ifdef CONFIG_SERIAL_8250_AU1X00
case UPIO_AU:
#endif
+ case UPIO_DWAPB:
serial_out(up, offset, value);
(void)serial_in(up, UART_LCR); /* safe, no side-effects */
break;
@@ -1383,6 +1399,19 @@ static irqreturn_t serial8250_interrupt(
handled = 1;
end = NULL;
+ } else if (up->port.iotype == UPIO_DWAPB &&
+ (iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
+ /* The DesignWare APB UART has an Busy Detect (0x07)
+ * interrupt meaning an LCR write attempt occured while the
+ * UART was busy. The interrupt must be cleared by reading
+ * the UART status register (USR) and the LCR re-written. */
+ unsigned int status;
+ status = *(volatile u32 *)up->port.private_data;
+ serial_out(up, UART_LCR, up->lcr);
+
+ handled = 1;
+
+ end = NULL;
} else if (end == NULL)
end = l;
@@ -2085,6 +2114,7 @@ static int serial8250_request_std_resour
case UPIO_TSI:
case UPIO_MEM32:
case UPIO_MEM:
+ case UPIO_DWAPB:
if (!up->port.mapbase)
break;
@@ -2122,6 +2152,7 @@ static void serial8250_release_std_resou
case UPIO_TSI:
case UPIO_MEM32:
case UPIO_MEM:
+ case UPIO_DWAPB:
if (!up->port.mapbase)
break;
@@ -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;
diff --git a/drivers/serial/8250.h b/drivers/serial/8250.h
diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index f84982e..f5b6036 100644
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -2057,6 +2057,7 @@ uart_report_port(struct uart_driver *drv
case UPIO_MEM32:
case UPIO_AU:
case UPIO_TSI:
+ case UPIO_DWAPB:
snprintf(address, sizeof(address),
"MMIO 0x%lx", port->mapbase);
break;
@@ -2401,6 +2402,7 @@ int uart_match_port(struct uart_port *po
case UPIO_MEM32:
case UPIO_AU:
case UPIO_TSI:
+ case UPIO_DWAPB:
return (port1->mapbase == port2->mapbase);
}
return 0;
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cf23813..8cdd326 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -230,6 +230,7 @@ #define UPIO_MEM (2)
#define UPIO_MEM32 (3)
#define UPIO_AU (4) /* Au1x00 type IO */
#define UPIO_TSI (5) /* Tsi108/109 type IO */
+#define UPIO_DWAPB (6) /* DesignWare APB UART */
unsigned int read_status_mask; /* driver specific */
unsigned int ignore_status_mask; /* driver specific */
@@ -276,6 +277,7 @@ #define UPF_USR_MASK ((__force upf_t) (
struct device *dev; /* parent device */
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char unused[3];
+ void *private_data; /* generic platform data pointer */
};
/*
diff --git a/include/linux/serial_reg.h b/include/linux/serial_reg.h
index 3c8a6aa..1c5ed7d 100644
--- a/include/linux/serial_reg.h
+++ b/include/linux/serial_reg.h
@@ -38,6 +38,8 @@ #define UART_IIR_THRI 0x02 /* Transmitt
#define UART_IIR_RDI 0x04 /* Receiver data interrupt */
#define UART_IIR_RLSI 0x06 /* Receiver line status interrupt */
+#define UART_IIR_BUSY 0x07 /* DesignWare APB Busy Detect */
+
#define UART_FCR 2 /* Out: FIFO Control Register */
#define UART_FCR_ENABLE_FIFO 0x01 /* Enable the FIFO */
#define UART_FCR_CLEAR_RCVR 0x02 /* Clear the RCVR FIFO */
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(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.
WBR, Sergei
On Thu, 15 Feb 2007 13:26:29 -0600
Marc St-Jean <[email protected]> wrote:
> + status = *(volatile u32 *)up->port.private_data;
It distresses me that this patch uses a variable which this patch
doesn't initialise anywhere. It isn't complete.
The sub-driver code whch sets up this field shuld be included in the
patch, no?
Hello.
Andrew Morton wrote:
>>+ status = *(volatile u32 *)up->port.private_data;
> It distresses me that this patch uses a variable which this patch
> doesn't initialise anywhere. It isn't complete.
I assume this gets passed via early_serial_setup(). Marc?
> The sub-driver code whch sets up this field shuld be included in the
> patch, no?
Hardly so, this code (not a subdriver) resides under arch/mips/ I think.
WBR, Sergei