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authorGeert Uytterhoeven <geert+renesas@glider.be>2015-11-16 17:22:16 +0100
committerGeert Uytterhoeven <geert+renesas@glider.be>2015-12-17 11:18:38 +0100
commitb4a5c459088b724734573a550c9da42a9a19c9d0 (patch)
treea56138443acd167edb8faf05ffc2a15e65fb0861 /drivers/tty
parent6c51332dfc23fc7c2c58244e35d36744db202077 (diff)
downloadlinux-b4a5c459088b724734573a550c9da42a9a19c9d0.tar.bz2
serial: sh-sci: Merge sci_scbrr_calc() and sci_baud_calc_hscif()
For low bit rates, the for-loop that reduces the divider returned by sci_scbrr_calc() and picks the clock select value may terminate without finding suitable values, leading to out-of-range divider and clock select values. sci_baud_calc_hscif() doesn't suffer from this problem, as it correctly uses clamp(). Since there are only two relevant differences between HSCIF and other variants w.r.t. bit rate configuration (fixed vs. variable sample rate, and an additional factor of two), sci_scbrr_calc() and sci_baud_calc_hscif() can be merged, fixing the issue with out-of-range values. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/sh-sci.c42
1 files changed, 19 insertions, 23 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index c3a193616484..d89d4b7576cf 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -1860,20 +1860,24 @@ static void sci_shutdown(struct uart_port *port)
sci_free_irq(s);
}
-static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps,
- unsigned long freq)
+/* 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)
{
- return DIV_ROUND_CLOSEST(freq, s->sampling_rate * bps) - 1;
-}
-
-/* calculate sample rate, BRR, and clock select for HSCIF */
-static void sci_baud_calc_hscif(struct sci_port *s, unsigned int bps,
- unsigned long freq, int *brr,
- unsigned int *srr, unsigned int *cks)
-{
- unsigned int sr, br, prediv, scrate, c;
+ unsigned int min_sr, max_sr, shift, sr, br, prediv, scrate, c;
int err, min_err = INT_MAX;
+ if (s->sampling_rate) {
+ min_sr = max_sr = s->sampling_rate;
+ shift = 0;
+ } else {
+ /* HSCIF has a variable sample rate */
+ min_sr = 8;
+ max_sr = 32;
+ shift = 1;
+ }
+
/*
* Find the combination of sample rate and clock select with the
* smallest deviation from the desired baud rate.
@@ -1889,10 +1893,10 @@ static void sci_baud_calc_hscif(struct sci_port *s, unsigned int bps,
* (|D - 0.5| / N * (1 + F))|
* NOTE: Usually, treat D for 0.5, F is 0 by this calculation.
*/
- for (sr = 32; sr >= 8; sr--) {
+ for (sr = max_sr; sr >= min_sr; sr--) {
for (c = 0; c <= 3; c++) {
/* integerized formulas from HSCIF documentation */
- prediv = sr * (1 << (2 * c + 1));
+ prediv = sr * (1 << (2 * c + shift));
/*
* We need to calculate:
@@ -1974,16 +1978,8 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
max_baud = port->uartclk ? port->uartclk / 16 : 115200;
baud = uart_get_baud_rate(port, termios, old, 0, max_baud);
- if (likely(baud && port->uartclk)) {
- if (s->cfg->type == PORT_HSCIF) {
- sci_baud_calc_hscif(s, baud, port->uartclk, &t, &srr,
- &cks);
- } else {
- t = sci_scbrr_calc(s, baud, port->uartclk);
- for (cks = 0; t >= 256 && cks <= 3; cks++)
- t >>= 2;
- }
- }
+ if (likely(baud && port->uartclk))
+ sci_scbrr_calc(s, baud, port->uartclk, &t, &srr, &cks);
sci_port_enable(s);