--- serial-old.c	Wed Feb 20 17:21:45 2002
+++ serial.c	Wed Feb 20 17:26:16 2002
@@ -57,6 +57,9 @@
  * 10/00: add in optional software flow control for serial console.
  *	  Kanoj Sarcar <kanoj@sgi.com>  (Modified by Theodore Ts'o)
  *
+ * 02/02: 16C950 automatic clock frequency detection.
+ *	  Fabrizio Gennari <fabrizio.gennari@philips.com>
+ *
  */
 
 static char *serial_version = "5.05c";
@@ -3510,6 +3513,64 @@
 	return count;
 }
 
+/* The algorithm for detecting the clock frequency in 16C950 UARTs
+   was suggested by Anna Trett of Oxford Semiconductor */
+
+static int autodetect_16c950_clock(struct async_struct *info,
+				   struct serial_state *state)
+{
+	unsigned char old_fcr, old_mcr, old_dll, old_dlm, old_tcr;
+	int nchar=0,num=0,result;
+	struct timeval before,after;
+	int husec_elapsed;
+
+	old_fcr = serial_inp(info, UART_FCR);
+	old_mcr = serial_inp(info, UART_MCR);
+	serial_outp(info, UART_FCR, 
+		    UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
+	serial_outp(info, UART_MCR, UART_MCR_LOOP);
+	serial_outp(info, UART_LCR, UART_LCR_DLAB);
+	old_dll = serial_inp(info, UART_DLL);
+	old_dlm = serial_inp(info, UART_DLM);
+	old_tcr = serial_inp(info, UART_TCR);
+	serial_outp(info, UART_DLL, 0x01);
+	serial_outp(info, UART_DLM, 0x00);
+	serial_outp(info, UART_TCR, 0x00);
+	serial_outp(info, UART_LCR, 0x03);
+	printk(KERN_INFO "Autodetecting...\n");
+
+	/* The best thing to do would be to loop for
+	a set number of jiffies. But the variable jiffies does
+	not increment here. So, we just loop until a set number 
+	of characters is received (it should take 1 sec if a standard
+	clock is used) and measure how many hundreds of usecs it took,
+	storing it in husec_elapsed */
+
+	do_gettimeofday(&before);
+	do{
+		serial_outp(info, UART_TX, (num++)&0xFF);
+		if (serial_inp(info, UART_LSR) & UART_LSR_DR){
+		  nchar++;
+		  serial_inp(info, UART_RX);
+		}
+	}while(nchar<11520 && num < 1000000);
+	do_gettimeofday(&after);
+	husec_elapsed=(after.tv_sec-before.tv_sec)*10000+(after.tv_usec-before.tv_usec)/100;
+	printk(KERN_INFO "num %u nchar %u elapsed %u\n",num,nchar,husec_elapsed);
+  	serial_outp(info, UART_FCR, old_fcr);
+	serial_outp(info, UART_MCR, old_mcr);
+	serial_outp(info, UART_LCR, UART_LCR_DLAB);
+	serial_outp(info, UART_DLL, old_dll);
+	serial_outp(info, UART_DLM, old_dlm);
+	serial_outp(info, UART_TCR, old_tcr);
+
+	nchar = nchar*10*10000;
+	printk(KERN_INFO "nchar %u\n",nchar);
+	result = nchar/husec_elapsed;
+	printk(KERN_INFO "res %u\n",result);
+	return result;
+}
+
 /*
  * This is a helper routine to autodetect StarTech/Exar/Oxsemi UART's.
  * When this function is called we know it is at least a StarTech
@@ -3556,6 +3617,7 @@
 			state->type = PORT_16C950;
 			state->revision = serial_icr_read(info, UART_REV) |
 				(scratch3 << 8);
+			state->baud_base=autodetect_16c950_clock(info,state);
 			return;
 		}
 	}