Re: [PATCH] Make the Startech UART detection 'more correct'.

[Tom Rini]

On Tue, Sep 09, 2003 at 05:18:59PM +0100, Russell King wrote:

> On Mon, Sep 08, 2003 at 01:54:31PM -0700, Tom Rini wrote:
> > Hello.  The following patches (vs 2.4 and 2.6) make the Startech UART
> > detection 'more correct'  The problem is that on with the Motorola
> > MPC82xx line (8245 for example) it has an internal DUART that it claims
> > to be PC16550D compatible, and it has an additional EFR (Enhanced
> > Feature Register) at offset 0x2, like on the Startech UARTS.  However,
> > it is not a Startech, and when it's detected as such, FIFOs don't work.
> > The fix for this is that the Startech UARTs have a 32 byte FIFO [1] and
> > the MPC82xx DUARTs have a 16-byte FIFO [2], to check that the FIFO size
> > is correct for a Startech.
> 
> size_fifo() is claimed to be unreliable at detecting the FIFO size,
> so I don't feel safe about using it here.
> 
> I'd suggest something like:
> 
> 	serial_outp(port, UART_LCR, UART_LCR_DLAB);
> 	efr = serial_in(port, UART_EFR);
> 	if ((efr & 0xfc) == 0) {
> 		serial_out(port, UART_EFR, 0xac | (efr & 3));
> 		/* if top 6 bits return zero, its motorola */
> 		if (serial_in(port, UART_EFR) == (efr & 3)) {
> 			/* motorola port */
> 		} else {
> 			/* ST16C650V1 port */
> 		}
> 		/* restore old value */
> 		serial_outb(port, UART_EFR, efr);
> 	}

Okay, from Kumar Gala (cc'ed) I've got the following patch for 2.4:
===== drivers/char/serial.c 1.34 vs edited =====
--- 1.34/drivers/char/serial.c	Sun Jul  6 22:33:28 2003
+++ edited/drivers/char/serial.c	Tue Sep  9 16:50:22 2003
@@ -3741,7 +3741,10 @@
 		/* Check for Startech UART's */
 		serial_outp(info, UART_LCR, UART_LCR_DLAB);
 		if (serial_in(info, UART_EFR) == 0) {
-			state->type = PORT_16650;
+			serial_outp(info, UART_EFR, 0xA8);
+			if (serial_in(info, UART_EFR) != 0)
+				state->type = PORT_16650;
+			serial_outp(info, UART_EFR, 0);
 		} else {
 			serial_outp(info, UART_LCR, 0xBF);
 			if (serial_in(info, UART_EFR) == 0)

And I forward ported this up to 2.6 as:
===== drivers/serial/8250.c 1.36 vs edited =====
--- 1.36/drivers/serial/8250.c	Tue Sep  9 07:22:12 2003
+++ edited/drivers/serial/8250.c	Tue Sep  9 16:49:07 2003
@@ -469,8 +469,13 @@
 	 */
 	serial_outp(up, UART_LCR, UART_LCR_DLAB);
 	if (serial_in(up, UART_EFR) == 0) {
-		DEBUG_AUTOCONF("EFRv1 ");
-		up->port.type = PORT_16650;
+		serial_outp(up, UART_EFR, 0xA8);
+		if (serial_in(up, UART_EFR) != 0) {
+			DEBUG_AUTOCONF("EFRv1 ");
+			up->port.type = PORT_16650;
+		} else
+			DEBUG_AUTOCONF("Motorola 8xxx DUART ");
+		serial_outp(up, UART_EFR, 0);
 		return;
 	}

Better?

-- 
Tom Rini
http://gate.crashing.org/~trini/

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