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Date: Thu, 19 Nov 2015 19:38:59 +0100
From: Geert Uytterhoeven <geert+renesas@...der.be>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Simon Horman <horms@...ge.net.au>,
Magnus Damm <magnus.damm@...il.com>,
Yoshinori Sato <ysato@...rs.sourceforge.jp>,
Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc: linux-serial@...r.kernel.org, linux-sh@...r.kernel.org,
linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH 20/25] serial: sh-sci: Add support for optional BRG on (H)SCIF
Add support for the Baud Rate Generator for External Clock (BRG), as
found on some SCIF and HSCIF variants, which can improve baud rate range
and accuracy.
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
drivers/tty/serial/sh-sci.c | 82 ++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 77 insertions(+), 5 deletions(-)
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index f88aac684ed1e3b6..6b8f1675b9f6fadb 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -80,6 +80,8 @@ enum {
enum SCI_CLKS {
SCI_FCK, /* Functional Clock */
SCI_SCK, /* Optional External Clock */
+ SCI_INT_CLK, /* Optional BRG Internal Clock Source */
+ SCI_SCIF_CLK, /* Optional BRG External Clock Source */
SCI_NUM_CLKS
};
@@ -1955,6 +1957,40 @@ static int sci_sck_calc(struct sci_port *s, unsigned int bps,
return min_err;
}
+static int sci_brg_calc(struct sci_port *s, unsigned int bps,
+ unsigned long freq, unsigned int *dlr,
+ unsigned int *srr)
+{
+ unsigned int min_sr, max_sr, sr, dl;
+ int err, min_err = INT_MAX;
+
+ if (s->sampling_rate) {
+ /* SCIF has a fixed sampling rate */
+ min_sr = max_sr = s->sampling_rate / 2;
+ } else {
+ /* HSCIF has a variable 1/(8..32) sampling rate */
+ min_sr = 8;
+ max_sr = 32;
+ }
+
+ for (sr = max_sr; sr >= min_sr; sr--) {
+ dl = DIV_ROUND_CLOSEST(freq, sr * bps);
+ dl = clamp(dl, 1U, 65535U);
+
+ err = DIV_ROUND_CLOSEST(freq, sr * dl) - bps;
+ if (abs(err) >= abs(min_err))
+ continue;
+
+ min_err = err;
+ *dlr = dl;
+ *srr = sr - 1;
+ }
+
+ dev_dbg(s->port.dev, "BRG: %u%+d bps using DL %u SR %u\n", bps,
+ min_err, *dlr, *srr + 1);
+ return min_err;
+}
+
/* calculate sample rate, BRR, and clock select */
static int sci_scbrr_calc(struct sci_port *s, unsigned int bps,
unsigned int *brr, unsigned int *srr,
@@ -2036,8 +2072,8 @@ 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, sccks = 0;
- unsigned int brr1 = 255, cks1 = 0, srr1 = 15;
+ unsigned int brr = 255, cks = 0, srr = 15, dl = 0, sccks = 0;
+ unsigned int brr1 = 255, cks1 = 0, srr1 = 15, dl1 = 0;
struct sci_port *s = to_sci_port(port);
const struct plat_sci_reg *reg;
int min_err = INT_MAX, err;
@@ -2089,6 +2125,38 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
}
}
+ /* Optional BRG External Clock Source */
+ if (s->clk_rates[SCI_SCIF_CLK] && sci_getreg(port, SCDL)->size) {
+ err = sci_brg_calc(s, baud, s->clk_rates[SCI_SCIF_CLK], &dl1,
+ &srr1);
+ if (abs(err) < abs(min_err)) {
+ best_clk = SCI_SCIF_CLK;
+ scr_val = SCSCR_CKE1;
+ sccks = 0;
+ min_err = err;
+ dl = dl1;
+ srr = srr1;
+ if (!err)
+ goto done;
+ }
+ }
+
+ /* Optional BRG Internal Clock Source */
+ if (s->clk_rates[SCI_INT_CLK] && sci_getreg(port, SCDL)->size) {
+ err = sci_brg_calc(s, baud, s->clk_rates[SCI_INT_CLK], &dl1,
+ &srr1);
+ if (abs(err) < abs(min_err)) {
+ best_clk = SCI_INT_CLK;
+ scr_val = SCSCR_CKE1;
+ sccks = SCCKS_XIN;
+ min_err = err;
+ dl = dl1;
+ srr = srr1;
+ if (!min_err)
+ goto done;
+ }
+ }
+
/* Functional Clock and standard Bit Rate Register */
err = sci_scbrr_calc(s, baud, &brr1, &srr1, &cks1);
if (abs(err) < abs(min_err)) {
@@ -2108,8 +2176,10 @@ done:
sci_port_enable(s);
/* Program the optional External Baud Rate Generator (BRG) first */
- if (best_clk >= 0 && sci_getreg(port, SCCKS)->size)
+ if (best_clk >= 0 && sci_getreg(port, SCCKS)->size) {
+ serial_port_out(port, SCDL, dl);
serial_port_out(port, SCCKS, sccks);
+ }
sci_reset(port);
@@ -2118,8 +2188,8 @@ done:
if (best_clk >= 0) {
smr_val |= cks;
dev_dbg(port->dev,
- "SCR 0x%x SMR 0x%x BRR %u CKS 0x%x SRR %u\n",
- scr_val, smr_val, brr, sccks, srr);
+ "SCR 0x%x SMR 0x%x BRR %u CKS 0x%x DL %u SRR %u\n",
+ scr_val, smr_val, brr, sccks, dl, srr);
serial_port_out(port, SCSCR, scr_val);
serial_port_out(port, SCSMR, smr_val);
serial_port_out(port, SCBRR, brr);
@@ -2357,6 +2427,8 @@ static int sci_init_clocks(struct sci_port *sci_port, struct device *dev)
const char *clk_names[] = {
[SCI_FCK] = "fck",
[SCI_SCK] = "sck",
+ [SCI_INT_CLK] = "int_clk",
+ [SCI_SCIF_CLK] = "scif_clk",
};
struct clk *clk;
unsigned int i;
--
1.9.1
--
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