Re: [PATCH] serial driver PMC MSP71xx, kernel linux-mips.git master

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Hello.

Marc St-Jean wrote:
Fourth attempt at the serial driver patch for the PMC-Sierra MSP71xx device.

There are three different fixes:
1. Fix for DesignWare THRE errata
- Dropped our fix since the "8250-uart-backup-timer.patch" in the "mm"
tree also fixes it. This patch needs to be applied on top of "mm" patch.

2. Fix for Busy Detect on LCR write
- Changed the ordering of test in serial8250_interrupt().
- Combined test for UPIO_DWAPB with UPIO_MEM in serial8250_start_console().
- Renamed new uart_8250_port member to private_data.

3. Workaround for interrupt/data concurrency issue
- No changes since last patch.

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 3d91bfc..b309c4c 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) && in_irq())
+			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) {

Worth aligning this line with the opening paren of if... but's that's nitpicking. :-)

+			/* 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;

  	return 0;

   Still, shouldn't you be doing this in serial8250_timeout() also?
What IRQ numbers this UART is using, BTW?

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index cf23813..bd9711a 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -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 */

   One tab to many before *private_data...

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 */

   Oops, your mailer went and did it again. :-)

WBR, Sergei


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