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serial: sccnxp: Allow to use non-standard baud rates 

This patch adds support for the use of non-standard baud rates.
For these purposes, we use the built-in timer/counter.

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Alexander Shiyan 2018-12-20 09:19:30 +03:00 committed by Greg Kroah-Hartman
parent 4ce193fdba
commit efa0f49496
1 changed files with 19 additions and 3 deletions
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22
drivers/tty/serial/sccnxp.c
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@ -48,7 +48,6 @@
# define MR2_STOP1 (7 << 0)
# define MR2_STOP2 (0xf << 0)
#define SCCNXP_SR_REG (0x01)
#define SCCNXP_CSR_REG SCCNXP_SR_REG
# define SR_RXRDY (1 << 0)
# define SR_FULL (1 << 1)
# define SR_TXRDY (1 << 2)
@ -57,6 +56,8 @@
# define SR_PE (1 << 5)
# define SR_FE (1 << 6)
# define SR_BRK (1 << 7)
#define SCCNXP_CSR_REG (SCCNXP_SR_REG)
# define CSR_TIMER_MODE (0x0d)
#define SCCNXP_CR_REG (0x02)
# define CR_RX_ENABLE (1 << 0)
# define CR_RX_DISABLE (1 << 1)
@ -83,9 +84,12 @@
# define IMR_RXRDY (1 << 1)
# define ISR_TXRDY(x) (1 << ((x * 4) + 0))
# define ISR_RXRDY(x) (1 << ((x * 4) + 1))
#define SCCNXP_CTPU_REG (0x06)
#define SCCNXP_CTPL_REG (0x07)
#define SCCNXP_IPR_REG (0x0d)
#define SCCNXP_OPCR_REG SCCNXP_IPR_REG
#define SCCNXP_SOP_REG (0x0e)
#define SCCNXP_START_COUNTER_REG SCCNXP_SOP_REG
#define SCCNXP_ROP_REG (0x0f)
/* Route helpers */
@ -255,7 +259,7 @@ static int sccnxp_update_best_err(int a, int b, int *besterr)
{
int err = abs(a - b);
if ((*besterr < 0) || (*besterr > err)) {
if (*besterr > err) {
*besterr = err;
return 0;
}
@ -303,10 +307,22 @@ static const struct {
static int sccnxp_set_baud(struct uart_port *port, int baud)
{
struct sccnxp_port *s = dev_get_drvdata(port->dev);
int div_std, tmp_baud, bestbaud = baud, besterr = -1;
int div_std, tmp_baud, bestbaud = INT_MAX, besterr = INT_MAX;
struct sccnxp_chip *chip = s->chip;
u8 i, acr = 0, csr = 0, mr0 = 0;
/* Find divisor to load to the timer preset registers */
div_std = DIV_ROUND_CLOSEST(port->uartclk, 2 * 16 * baud);
if ((div_std >= 2) && (div_std <= 0xffff)) {
bestbaud = DIV_ROUND_CLOSEST(port->uartclk, 2 * 16 * div_std);
sccnxp_update_best_err(baud, bestbaud, &besterr);
csr = CSR_TIMER_MODE;
sccnxp_port_write(port, SCCNXP_CTPU_REG, div_std >> 8);
sccnxp_port_write(port, SCCNXP_CTPL_REG, div_std);
/* Issue start timer/counter command */
sccnxp_port_read(port, SCCNXP_START_COUNTER_REG);
}
/* Find best baud from table */
for (i = 0; baud_std[i].baud && besterr; i++) {
if (baud_std[i].mr0 && !(chip->flags & SCCNXP_HAVE_MR0))