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@xxxxxxxxxxxxxxxx>
---
drivers/tty/serial/sh-sci.c | 43 ++++++++++++++++++++++++++++++-------------
include/linux/serial_sci.h | 2 ++
2 files changed, 32 insertions(+), 13 deletions(-)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index d9b14d0..c65d37b 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -83,6 +83,7 @@ struct sci_port {
struct plat_sci_port *cfg;
int overrun_bit;
unsigned int error_mask;
+ unsigned int sampling_rate;
/* Break timer */
@@ -1763,10 +1764,13 @@ static void sci_shutdown(struct uart_port *port)
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:
@@ -1856,12 +1860,11 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
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;
}
@@ -2105,6 +2108,7 @@ static int sci_init_single(struct platform_device *dev,
{
struct uart_port *port = &sci_port->port;
const struct resource *res;
+ unsigned int sampling_rate;
unsigned int i;
int ret;
@@ -2147,28 +2151,47 @@ static int sci_init_single(struct platform_device *dev,
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)) {
@@ -2407,7 +2430,6 @@ static int sci_remove(struct platform_device *dev)
struct sci_port_info {
unsigned int type;
unsigned int regtype;
- unsigned int brr_algo;
};
static const struct of_device_id of_sci_match[] = {
@@ -2416,28 +2438,24 @@ static const struct of_device_id of_sci_match[] = {
.data = (void *)&(const struct sci_port_info) {
.type = PORT_SCIF,
.regtype = SCIx_SH4_SCIF_REGTYPE,
- .brr_algo = SCBRR_ALGO_2,
},
}, {
.compatible = "renesas,scifa",
.data = (void *)&(const struct sci_port_info) {
.type = PORT_SCIFA,
.regtype = SCIx_SCIFA_REGTYPE,
- .brr_algo = SCBRR_ALGO_4,
},
}, {
.compatible = "renesas,scifb",
.data = (void *)&(const struct sci_port_info) {
.type = PORT_SCIFB,
.regtype = SCIx_SCIFB_REGTYPE,
- .brr_algo = SCBRR_ALGO_4,
},
}, {
.compatible = "renesas,hscif",
.data = (void *)&(const struct sci_port_info) {
.type = PORT_HSCIF,
.regtype = SCIx_HSCIF_REGTYPE,
- .brr_algo = SCBRR_ALGO_6,
},
}, {
/* Terminator */
@@ -2482,7 +2500,6 @@ sci_parse_dt(struct platform_device *pdev, unsigned int *dev_id)
p->type = info->type;
p->regtype = info->regtype;
p->scscr = SCSCR_RE | SCSCR_TE;
- p->scbrr_algo_id = info->brr_algo;
return p;
}
diff --git a/include/linux/serial_sci.h b/include/linux/serial_sci.h
index 3d5d878..06dc806 100644
--- a/include/linux/serial_sci.h
+++ b/include/linux/serial_sci.h
@@ -11,6 +11,7 @@
#define SCIx_NOT_SUPPORTED (-1)
enum {
+ SCBRR_ALGO_NONE, /* Compute sampling rate in the driver */
SCBRR_ALGO_1, /* clk / (16 * bps) */
SCBRR_ALGO_2, /* DIV_ROUND_CLOSEST(clk, 32 * bps) - 1 */
SCBRR_ALGO_3, /* clk / (8 * bps) */
@@ -108,6 +109,7 @@ struct plat_sci_port {
upf_t flags; /* UPF_* flags */
unsigned long capabilities; /* Port features/capabilities */
+ unsigned int sampling_rate;
unsigned int scbrr_algo_id; /* SCBRR calculation algo */
unsigned int scscr; /* SCSCR initialization */
--
1.8.3.2
--
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