i.MX use u-boot baud rate and don't assume UART master clock

1) Change the i.MX serial driver to use the baud rate set in the
 u-boot environment

2) don't assume a 16MHz value for PERCLK1 in baud rate calculations

3) don't write a 1 to the RDR bit in the USR2 reg. (bit is not "write
 one to clear" like other status bits in the reg.)

Signed-off-by: Andrew Dyer <adyer@righthandtech.com>

diff --git a/cpu/arm920t/imx/serial.c b/cpu/arm920t/imx/serial.c
index 6c56acbfde5c7ee2a0130a488a3483ebc481dbbd..85f1167e36e2bfe73078cbc1bc40cabcf77ef1a1 100644 (file)
--- a/cpu/arm920t/imx/serial.c
+++ b/cpu/arm920t/imx/serial.c
@@ -52,6 +52,8 @@ struct imx_serial {
        volatile uint32_t uts;
 };
 
+DECLARE_GLOBAL_DATA_PTR;
+
 void serial_setbrg (void)
 {
        serial_init();
@@ -67,6 +69,9 @@ extern void imx_gpio_mode(int gpio_mode);
 int serial_init (void)
 {
        volatile struct imx_serial* base = (struct imx_serial *)UART_BASE;
+       unsigned int ufcr_rfdiv;
+       unsigned int refclk;
+
 #ifdef CONFIG_IMX_SERIAL1
        imx_gpio_mode(PC11_PF_UART1_TXD);
        imx_gpio_mode(PC12_PF_UART1_RXD);
@@ -95,11 +100,33 @@ int serial_init (void)
        /* Configure FIFOs */
        base->ufcr = 0xa81;
 
+       /* set the baud rate.
+        *
+        * baud * 16   x
+        * --------- = -
+        *  refclk     y
+        *
+        * x - 1 = UBIR
+        * y - 1 = UBMR
+        *
+        * each register is 16 bits wide. refclk max is 96 MHz
+        *
+        */
+
+       ufcr_rfdiv = ((base->ufcr) & UFCR_RFDIV) >> 7;
+       if (ufcr_rfdiv == 6)
+               ufcr_rfdiv = 7;
+       else
+               ufcr_rfdiv = 6 - ufcr_rfdiv;
+
+       refclk = get_PERCLK1();
+       refclk /= ufcr_rfdiv;
+
        /* Set the numerator value minus one of the BRM ratio */
-       base->ubir = (CONFIG_BAUDRATE / 100) - 1;
+       base->ubir = (gd->baudrate / 100) - 1;
 
        /* Set the denominator value minus one of the BRM ratio */
-       base->ubmr = 10000 - 1;
+       base->ubmr = (refclk/(16 * 100)) - 1;
 
        /* Set to 8N1 */
        base->ucr2 &= ~UCR2_PREN;
@@ -117,22 +144,21 @@ int serial_init (void)
 
        /* Clear status flags */
        base->usr2 |= USR2_ADET  |
-                 USR2_DTRF  |
-                 USR2_IDLE  |
-                 USR2_IRINT |
-                 USR2_WAKE  |
-                 USR2_RTSF  |
-                 USR2_BRCD  |
-                 USR2_ORE   |
-                 USR2_RDR;
+                     USR2_DTRF  |
+                     USR2_IDLE  |
+                     USR2_IRINT |
+                     USR2_WAKE  |
+                     USR2_RTSF  |
+                     USR2_BRCD  |
+                     USR2_ORE;
 
        /* Clear status flags */
        base->usr1 |= USR1_PARITYERR |
-                 USR1_RTSD      |
-                 USR1_ESCF      |
-                 USR1_FRAMERR   |
-                 USR1_AIRINT    |
-                 USR1_AWAKE;
+                     USR1_RTSD      |
+                     USR1_ESCF      |
+                     USR1_FRAMERR   |
+                     USR1_AIRINT    |
+                     USR1_AWAKE;
        return (0);
 }