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Tweak to support 1Mbaud and similar baudrates that require Mode16 instea... #26

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Tweak to support 1Mbaud and similar baudrates that require Mode16 instea... #26

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38 changes: 28 additions & 10 deletions drivers/tty/serial/omap-serial.c
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Original file line number Diff line number Diff line change
Expand Up @@ -181,25 +181,43 @@ static void serial_omap_enable_wakeup(struct uart_omap_port *up, bool enable)
pdata->enable_wakeup(up->dev, enable);
}

/*
* serial_omap_baud_is_mode16 - check if baud rate is MODE16X
* @port: uart port info
* @baud: baudrate for which mode needs to be determined
*
* Returns true if baud rate is MODE16X and false if MODE13X
* Original table in OMAP TRM named "UART Mode Baud Rates, Divisor Values,
* and Error Rates" determines modes not for all common baud rates.
* E.g. for 1000000 baud rate mode must be 16x, but according to that
* table it's determined as 13x.
*/
static bool
serial_omap_baud_is_mode16(struct uart_port *port, unsigned int baud)
{
unsigned int n13 = port->uartclk / (13 * baud);
unsigned int n16 = port->uartclk / (16 * baud);
int baudAbsDiff13 = baud - (port->uartclk / (13 * n13));
int baudAbsDiff16 = baud - (port->uartclk / (16 * n16));
if(baudAbsDiff13 < 0)
baudAbsDiff13 = -baudAbsDiff13;
if(baudAbsDiff16 < 0)
baudAbsDiff16 = -baudAbsDiff16;

return (baudAbsDiff13 > baudAbsDiff16);
}

/*
* serial_omap_get_divisor - calculate divisor value
* @port: uart port info
* @baud: baudrate for which divisor needs to be calculated.
*
* We have written our own function to get the divisor so as to support
* 13x mode. 3Mbps Baudrate as an different divisor.
* Reference OMAP TRM Chapter 17:
* Table 17-1. UART Mode Baud Rates, Divisor Values, and Error Rates
* referring to oversampling - divisor value
* baudrate 460,800 to 3,686,400 all have divisor 13
* except 3,000,000 which has divisor value 16
*/
static unsigned int
serial_omap_get_divisor(struct uart_port *port, unsigned int baud)
{
unsigned int divisor;

if (baud > OMAP_MODE13X_SPEED && baud != 3000000)
if (!serial_omap_baud_is_mode16(port, baud))
divisor = 13;
else
divisor = 16;
Expand Down Expand Up @@ -893,7 +911,7 @@ serial_omap_set_termios(struct uart_port *port, struct ktermios *termios,
serial_out(up, UART_EFR, up->efr);
serial_out(up, UART_LCR, cval);

if (baud > 230400 && baud != 3000000)
if (!serial_omap_baud_is_mode16(port, baud))
up->mdr1 = UART_OMAP_MDR1_13X_MODE;
else
up->mdr1 = UART_OMAP_MDR1_16X_MODE;
Expand Down