serial: sh-sci: Rework baud rate calculation
Computing the baud rate register value requires knowledge of the
hardware sampling rate. This information is currently encoded in a baud
rate calculation algorithm ID passed through platform data. However, it
can be derived from the port type directly in most cases.
Compute the sampling rate internally in the driver if the baud rate
calculation algorithm ID isn't specified, and allow platforms to
override the sampling rate through platform data in special cases (this
is only required for SCIFA ports on sh7723 and sh7724, the reason needs
to be investigated).
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index d5239d5..e4bf0e4 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -65,6 +65,7 @@
struct plat_sci_port *cfg;
int overrun_bit;
unsigned int error_mask;
+ unsigned int sampling_rate;
/* Break timer */
@@ -1750,10 +1751,13 @@
sci_free_irq(s);
}
-static unsigned int sci_scbrr_calc(unsigned int algo_id, unsigned int bps,
+static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps,
unsigned long freq)
{
- switch (algo_id) {
+ if (s->sampling_rate)
+ return DIV_ROUND_CLOSEST(freq, s->sampling_rate * bps) - 1;
+
+ switch (s->cfg->scbrr_algo_id) {
case SCBRR_ALGO_1:
return freq / (16 * bps);
case SCBRR_ALGO_2:
@@ -1843,12 +1847,11 @@
baud = uart_get_baud_rate(port, termios, old, 0, max_baud);
if (likely(baud && port->uartclk)) {
- if (s->cfg->scbrr_algo_id == SCBRR_ALGO_6) {
+ if (s->cfg->type == PORT_HSCIF) {
sci_baud_calc_hscif(baud, port->uartclk, &t, &srr,
&cks);
} else {
- t = sci_scbrr_calc(s->cfg->scbrr_algo_id, baud,
- port->uartclk);
+ t = sci_scbrr_calc(s, baud, port->uartclk);
for (cks = 0; t >= 256 && cks <= 3; cks++)
t >>= 2;
}
@@ -2092,6 +2095,7 @@
{
struct uart_port *port = &sci_port->port;
const struct resource *res;
+ unsigned int sampling_rate;
unsigned int i;
int ret;
@@ -2143,28 +2147,47 @@
case PORT_SCIFB:
port->fifosize = 256;
sci_port->overrun_bit = 9;
+ sampling_rate = 16;
break;
case PORT_HSCIF:
port->fifosize = 128;
+ sampling_rate = 0;
sci_port->overrun_bit = 0;
break;
case PORT_SCIFA:
port->fifosize = 64;
sci_port->overrun_bit = 9;
+ sampling_rate = 16;
break;
case PORT_SCIF:
port->fifosize = 16;
- if (p->regtype == SCIx_SH7705_SCIF_REGTYPE)
+ if (p->regtype == SCIx_SH7705_SCIF_REGTYPE) {
sci_port->overrun_bit = 9;
- else
+ sampling_rate = 16;
+ } else {
sci_port->overrun_bit = 0;
+ sampling_rate = 32;
+ }
break;
default:
port->fifosize = 1;
sci_port->overrun_bit = 5;
+ sampling_rate = 32;
break;
}
+ /* Set the sampling rate if the baud rate calculation algorithm isn't
+ * specified.
+ */
+ if (p->scbrr_algo_id == SCBRR_ALGO_NONE) {
+ /* SCIFA on sh7723 and sh7724 need a custom sampling rate that
+ * doesn't match the SoC datasheet, this should be investigated.
+ * Let platform data override the sampling rate for now.
+ */
+ sci_port->sampling_rate = p->sampling_rate ? p->sampling_rate
+ : sampling_rate;
+ }
+
if (!early) {
sci_port->iclk = clk_get(&dev->dev, "sci_ick");
if (IS_ERR(sci_port->iclk)) {