diff options
Diffstat (limited to 'drivers/tty/serial')
-rw-r--r-- | drivers/tty/serial/msm_serial.c | 99 |
1 files changed, 66 insertions, 33 deletions
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 074c797..b7d80bd 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -861,37 +861,72 @@ struct msm_baud_map { }; static const struct msm_baud_map * -msm_find_best_baud(struct uart_port *port, unsigned int baud) +msm_find_best_baud(struct uart_port *port, unsigned int baud, + unsigned long *rate) { - unsigned int i, divisor; - const struct msm_baud_map *entry; + struct msm_port *msm_port = UART_TO_MSM(port); + unsigned int divisor, result; + unsigned long target, old, best_rate = 0, diff, best_diff = ULONG_MAX; + const struct msm_baud_map *entry, *end, *best; static const struct msm_baud_map table[] = { - { 1536, 0x00, 1 }, - { 768, 0x11, 1 }, - { 384, 0x22, 1 }, - { 192, 0x33, 1 }, - { 96, 0x44, 1 }, - { 48, 0x55, 1 }, - { 32, 0x66, 1 }, - { 24, 0x77, 1 }, - { 16, 0x88, 1 }, - { 12, 0x99, 6 }, - { 8, 0xaa, 6 }, - { 6, 0xbb, 6 }, - { 4, 0xcc, 6 }, - { 3, 0xdd, 8 }, - { 2, 0xee, 16 }, { 1, 0xff, 31 }, - { 0, 0xff, 31 }, + { 2, 0xee, 16 }, + { 3, 0xdd, 8 }, + { 4, 0xcc, 6 }, + { 6, 0xbb, 6 }, + { 8, 0xaa, 6 }, + { 12, 0x99, 6 }, + { 16, 0x88, 1 }, + { 24, 0x77, 1 }, + { 32, 0x66, 1 }, + { 48, 0x55, 1 }, + { 96, 0x44, 1 }, + { 192, 0x33, 1 }, + { 384, 0x22, 1 }, + { 768, 0x11, 1 }, + { 1536, 0x00, 1 }, }; - divisor = uart_get_divisor(port, baud); + best = table; /* Default to smallest divider */ + target = clk_round_rate(msm_port->clk, 16 * baud); + divisor = DIV_ROUND_CLOSEST(target, 16 * baud); + + end = table + ARRAY_SIZE(table); + entry = table; + while (entry < end) { + if (entry->divisor <= divisor) { + result = target / entry->divisor / 16; + diff = abs(result - baud); + + /* Keep track of best entry */ + if (diff < best_diff) { + best_diff = diff; + best = entry; + best_rate = target; + } - for (i = 0, entry = table; i < ARRAY_SIZE(table); i++, entry++) - if (entry->divisor <= divisor) - break; + if (result == baud) + break; + } else if (entry->divisor > divisor) { + old = target; + target = clk_round_rate(msm_port->clk, old + 1); + /* + * The rate didn't get any faster so we can't do + * better at dividing it down + */ + if (target == old) + break; + + /* Start the divisor search over at this new rate */ + entry = table; + divisor = DIV_ROUND_CLOSEST(target, 16 * baud); + continue; + } + entry++; + } - return entry; /* Default to smallest divider */ + *rate = best_rate; + return best; } static int msm_set_baud_rate(struct uart_port *port, unsigned int baud, @@ -900,22 +935,20 @@ static int msm_set_baud_rate(struct uart_port *port, unsigned int baud, unsigned int rxstale, watermark, mask; struct msm_port *msm_port = UART_TO_MSM(port); const struct msm_baud_map *entry; - unsigned long flags; - - entry = msm_find_best_baud(port, baud); - - msm_write(port, entry->code, UART_CSR); - - if (baud > 460800) - port->uartclk = baud * 16; + unsigned long flags, rate; flags = *saved_flags; spin_unlock_irqrestore(&port->lock, flags); - clk_set_rate(msm_port->clk, port->uartclk); + entry = msm_find_best_baud(port, baud, &rate); + clk_set_rate(msm_port->clk, rate); + baud = rate / 16 / entry->divisor; spin_lock_irqsave(&port->lock, flags); *saved_flags = flags; + port->uartclk = rate; + + msm_write(port, entry->code, UART_CSR); /* RX stale watermark */ rxstale = entry->rxstale; |