[PATCH 18/25] serial: sh-sci: Prepare for multiple clocks and baud rate generators

Geert Uytterhoeven
2015-11-19T18:40:26Z

Refactor the clock and baud rate parameter code to ease adding support
for multiple clocks and baud rate generators later.
sci_scbrr_calc() now returns the bit rate error, so it can be compared
to the bit rate error for other baud rate generators.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
drivers/tty/serial/sh-sci.c | 176 ++++++++++++++++++++++++++++++--------------
1 file changed, 120 insertions(+), 56 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 726c96d5a511c222..12800e52f41953dc 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2,6 +2,7 @@
* SuperH on-chip serial module support. (SCI with no FIFO / with FIFO)
*
* Copyright (C) 2002 - 2011 Paul Mundt
+ * Copyright (C) 2015 Glider bvba
* Modified to support SH7720 SCIF. Markus Brunner, Mark Jonas (Jul 2007).
*
* based off of the old drivers/char/sh-sci.c by:
@@ -76,6 +77,11 @@ enum {
((port)->irqs[SCIx_ERI_IRQ] && \
((port)->irqs[SCIx_RXI_IRQ] < 0))

+enum SCI_CLKS {
+ SCI_FCK, /* Functional Clock */
+ SCI_NUM_CLKS
+};
+
struct sci_port {
struct uart_port port;

@@ -92,8 +98,9 @@ struct sci_port {
struct timer_list break_timer;
int break_flag;

- /* Function clock */
- struct clk *fclk;
+ /* Clocks */
+ struct clk *clks[SCI_NUM_CLKS];
+ unsigned long clk_rates[SCI_NUM_CLKS];

int irqs[SCIx_NR_IRQS];
char *irqstr[SCIx_NR_IRQS];
@@ -496,17 +503,24 @@ static int sci_probe_regmap(struct plat_sci_port *cfg)

static void sci_port_enable(struct sci_port *sci_port)
{
+ unsigned int i;
+
if (!sci_port->port.dev)
return;

pm_runtime_get_sync(sci_port->port.dev);

- clk_prepare_enable(sci_port->fclk);
- sci_port->port.uartclk = clk_get_rate(sci_port->fclk);
+ for (i = 0; i < SCI_NUM_CLKS; i++) {
+ clk_prepare_enable(sci_port->clks[i]);
+ sci_port->clk_rates[i] = clk_get_rate(sci_port->clks[i]);
+ }
+ sci_port->port.uartclk = sci_port->clk_rates[SCI_FCK];
}

static void sci_port_disable(struct sci_port *sci_port)
{
+ unsigned int i;
+
if (!sci_port->port.dev)
return;

@@ -518,7 +532,8 @@ static void sci_port_disable(struct sci_port *sci_port)
del_timer_sync(&sci_port->break_timer);
sci_port->break_flag = 0;

- clk_disable_unprepare(sci_port->fclk);
+ for (i = SCI_NUM_CLKS; i-- > 0; )
+ clk_disable_unprepare(sci_port->clks[i]);

pm_runtime_put_sync(sci_port->port.dev);
}
@@ -1657,6 +1672,7 @@ static int sci_notifier(struct notifier_block *self,
{
struct sci_port *sci_port;
unsigned long flags;
+ unsigned int i;

sci_port = container_of(self, struct sci_port, freq_transition);

@@ -1664,7 +1680,9 @@ static int sci_notifier(struct notifier_block *self,
struct uart_port *port = &sci_port->port;

spin_lock_irqsave(&port->lock, flags);
- port->uartclk = clk_get_rate(sci_port->fclk);
+ for (i = 0; i < SCI_NUM_CLKS; i++)
+ sci_port->clk_rates[i] =
+ clk_get_rate(sci_port->clks[i]);
spin_unlock_irqrestore(&port->lock, flags);
}

@@ -1907,11 +1925,12 @@ static void sci_shutdown(struct uart_port *port)
}

/* calculate sample rate, BRR, and clock select */
-static void sci_scbrr_calc(struct sci_port *s, unsigned int bps,
- unsigned long freq, int *brr, unsigned int *srr,
- unsigned int *cks)
+static int sci_scbrr_calc(struct sci_port *s, unsigned int bps,
+ unsigned int *brr, unsigned int *srr,
+ unsigned int *cks)
{
unsigned int min_sr, max_sr, shift, sr, br, a, b, c;
+ unsigned long freq = s->clk_rates[SCI_FCK];
int err, min_err = INT_MAX;

if (s->sampling_rate) {
@@ -1963,6 +1982,7 @@ static void sci_scbrr_calc(struct sci_port *s, unsigned int bps,

dev_dbg(s->port.dev, "BRR: %u%+d bps using N %u SR %u cks %u\n", bps,
min_err, *brr, *srr + 1, *cks);
+ return min_err;
}

static void sci_reset(struct uart_port *port)
@@ -1984,11 +2004,14 @@ static void sci_reset(struct uart_port *port)
static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
struct ktermios *old)
{
+ unsigned int baud, smr_val = 0, scr_val = 0, i;
+ unsigned int brr = 255, cks = 0, srr = 15;
+ unsigned int brr1 = 255, cks1 = 0, srr1 = 15;
struct sci_port *s = to_sci_port(port);
const struct plat_sci_reg *reg;
- unsigned int baud, smr_val = 0, max_baud, cks = 0;
- int t = -1;
- unsigned int srr = 15;
+ int min_err = INT_MAX, err;
+ unsigned long max_freq = 0;
+ int best_clk = -1;

if ((termios->c_cflag & CSIZE) == CS7)
smr_val |= SCSMR_CHR;
@@ -2007,35 +2030,59 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
* that the previous boot loader has enabled required clocks and
* setup the baud rate generator hardware for us already.
*/
- if (port->uartclk)
- max_baud = port->uartclk / max(s->sampling_rate, 8U);
- else
- max_baud = 115200;
+ if (!port->uartclk) {
+ baud = uart_get_baud_rate(port, termios, old, 0, 115200);
+ goto done;
+ }

- baud = uart_get_baud_rate(port, termios, old, 0, max_baud);
- if (likely(baud && port->uartclk))
- sci_scbrr_calc(s, baud, port->uartclk, &t, &srr, &cks);
+ for (i = 0; i < SCI_NUM_CLKS; i++)
+ max_freq = max(max_freq, s->clk_rates[i]);
+
+ baud = uart_get_baud_rate(port, termios, old, 0,
+ max_freq / max(s->sampling_rate, 8U));
+ if (!baud)
+ goto done;
+
+ /* Functional Clock and standard Bit Rate Register */
+ err = sci_scbrr_calc(s, baud, &brr1, &srr1, &cks1);
+ if (abs(err) < abs(min_err)) {
+ best_clk = SCI_FCK;
+ min_err = err;
+ brr = brr1;
+ srr = srr1;
+ cks = cks1;
+ }
+
+done:
+ if (best_clk >= 0)
+ dev_dbg(port->dev, "Using clk %pC for %u%+d bps\n",
+ s->clks[best_clk], baud, min_err);

sci_port_enable(s);

sci_reset(port);

- smr_val |= serial_port_in(port, SCSMR) & SCSMR_CKS;
-
uart_update_timeout(port, termios->c_cflag, baud);

- dev_dbg(port->dev, "%s: SMR %x, cks %x, t %x, SCSCR %x\n",
- __func__, smr_val, cks, t, s->cfg->scscr);
-
- if (t >= 0) {
- serial_port_out(port, SCSMR, (smr_val & ~SCSMR_CKS) | cks);
- serial_port_out(port, SCBRR, t);
- reg = sci_getreg(port, HSSRR);
- if (reg->size)
+ if (best_clk >= 0) {
+ smr_val |= cks;
+ dev_dbg(port->dev, "SMR 0x%x BRR %u SRR %u\n", smr_val, brr,
+ srr);
+ serial_port_out(port, SCSMR, smr_val);
+ serial_port_out(port, SCBRR, brr);
+ if (sci_getreg(port, HSSRR)->size)
serial_port_out(port, HSSRR, srr | HSCIF_SRE);
- udelay((1000000+(baud-1)) / baud); /* Wait one bit interval */
- } else
+
+ /* Wait one bit interval */
+ udelay((1000000 + (baud - 1)) / baud);
+ } else {
+ /* Don't touch the bit rate configuration */
+ scr_val = s->cfg->scscr & (SCSCR_CKE1 | SCSCR_CKE0);
+ smr_val |= serial_port_in(port, SCSMR) & SCSMR_CKS;
+ dev_dbg(port->dev, "SCR 0x%x SMR 0x%x\n", scr_val, smr_val);
+ serial_port_out(port, SCSCR, scr_val);
serial_port_out(port, SCSMR, smr_val);
+ }

sci_init_pins(port, termios->c_cflag);

@@ -2060,7 +2107,9 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
serial_port_out(port, SCFCR, ctrl);
}

- serial_port_out(port, SCSCR, s->cfg->scscr);
+ scr_val |= s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0);
+ dev_dbg(port->dev, "SCSCR 0x%x\n", scr_val);
+ serial_port_out(port, SCSCR, scr_val);

#ifdef CONFIG_SERIAL_SH_SCI_DMA
/*
@@ -2252,33 +2301,48 @@ static struct uart_ops sci_uart_ops = {

static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
{
- /* Get the SCI functional clock. It's called "fck" on ARM. */
- sci_port->fclk = devm_clk_get(dev, "fck");
- if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER)
- return -EPROBE_DEFER;
- if (!IS_ERR(sci_port->fclk))
- return 0;
+ const char *clk_names[] = {
+ [SCI_FCK] = "fck",
+ };
+ struct clk *clk;
+ unsigned int i;

- /*
- * But it used to be called "sci_ick", and we need to maintain DT
- * backward compatibility.
- */
- sci_port->fclk = devm_clk_get(dev, "sci_ick");
- if (PTR_ERR(sci_port->fclk) == -EPROBE_DEFER)
- return -EPROBE_DEFER;
- if (!IS_ERR(sci_port->fclk))
- return 0;
+ for (i = 0; i < SCI_NUM_CLKS; i++) {
+ clk = devm_clk_get(dev, clk_names[i]);
+ if (PTR_ERR(clk) == -EPROBE_DEFER)
+ return -EPROBE_DEFER;

- /*
- * Not all SH platforms declare a clock lookup entry for SCI devices,
- * in which case we need to get the global "peripheral_clk" clock.
- */
- sci_port->fclk = devm_clk_get(dev, "peripheral_clk");
- if (!IS_ERR(sci_port->fclk))
- return 0;
+ if (IS_ERR(clk) && i == SCI_FCK) {
+ /*
+ * "fck" used to be called "sci_ick", and we need to
+ * maintain DT backward compatibility.
+ */
+ clk = devm_clk_get(dev, "sci_ick");
+ if (PTR_ERR(clk) == -EPROBE_DEFER)
+ return -EPROBE_DEFER;
+
+ if (!IS_ERR(clk))
+ goto found;
+
+ /*
+ * Not all SH platforms declare a clock lookup entry
+ * for SCI devices, in which case we need to get the
+ * global "peripheral_clk" clock.
+ */
+ clk = devm_clk_get(dev, "peripheral_clk");
+ if (!IS_ERR(clk))
+ goto found;
+
+ dev_err(dev, "failed to get functional clock\n");
+ return PTR_ERR(clk);
+ }

- dev_err(dev, "failed to get functional clock\n");
- return PTR_ERR(sci_port->fclk);
+found:
+ if (!IS_ERR(clk))
+ dev_dbg(dev, "clk %u is %pC rate %pCr\n", i, clk, clk);
+ sci_port->clks[i] = IS_ERR(clk) ? NULL : clk;
+ }
+ return 0;
}

static int sci_init_single(struct platform_device *dev,
--
1.9.1