diff options
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/sh-sci.c | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 77e0a582da44..c490c51d6032 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1870,7 +1870,7 @@ static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps, static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr, unsigned int *srr, unsigned int *cks) { - unsigned int sr, br, c; + unsigned int sr, br, prediv, scrate, c; int err, recv_margin; int min_err = 1000; /* 100% */ int recv_max_margin = 0; @@ -1880,12 +1880,25 @@ static void sci_baud_calc_hscif(unsigned int bps, unsigned long freq, int *brr, for (sr = 8; sr <= 32; sr++) { for (c = 0; c <= 3; c++) { /* integerized formulas from HSCIF documentation */ - br = DIV_ROUND_CLOSEST(freq, (sr * - (1 << (2 * c + 1)) * bps)); + prediv = sr * (1 << (2 * c + 1)); + + /* + * We need to calculate: + * + * br = freq / (prediv * bps) clamped to [1..256] + * err = (freq / (br * prediv * bps / 1000)) - 1000 + * + * Watch out for overflow when calculating the desired + * sampling clock rate! + */ + if (bps > UINT_MAX / prediv) + break; + + scrate = prediv * bps; + br = DIV_ROUND_CLOSEST(freq, scrate); br = clamp(br, 1U, 256U); - err = DIV_ROUND_CLOSEST(freq, (br * bps * sr * - (1 << (2 * c + 1)) / 1000)) - - 1000; + err = DIV_ROUND_CLOSEST(freq, (br * scrate) / 1000) - + 1000; /* Calc recv margin * M: Receive margin (%) * N: Ratio of bit rate to clock (N = sampling rate) |