From ec09c5eb491834d4011c72538e58d8b7096076bd Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Fri, 6 Dec 2013 10:59:20 +0100 Subject: [PATCH] serial: sh-sci: Rework baud rate calculation Computing the baud rate register value requires knowledge of the hardware sampling rate. This information is currently encoded in a baud rate calculation algorithm ID passed through platform data. However, it can be derived from the port type directly in most cases. Compute the sampling rate internally in the driver if the baud rate calculation algorithm ID isn't specified, and allow platforms to override the sampling rate through platform data in special cases (this is only required for SCIFA ports on sh7723 and sh7724, the reason needs to be investigated). Signed-off-by: Laurent Pinchart Acked-by: Greg Kroah-Hartman Signed-off-by: Simon Horman --- drivers/tty/serial/sh-sci.c | 37 ++++++++++++++++++++++++++++++------- include/linux/serial_sci.h | 2 ++ 2 files changed, 32 insertions(+), 7 deletions(-) diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index d5239d5ff98b..e4bf0e435af6 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -65,6 +65,7 @@ struct sci_port { struct plat_sci_port *cfg; int overrun_bit; unsigned int error_mask; + unsigned int sampling_rate; /* Break timer */ @@ -1750,10 +1751,13 @@ static void sci_shutdown(struct uart_port *port) sci_free_irq(s); } -static unsigned int sci_scbrr_calc(unsigned int algo_id, unsigned int bps, +static unsigned int sci_scbrr_calc(struct sci_port *s, unsigned int bps, unsigned long freq) { - switch (algo_id) { + if (s->sampling_rate) + return DIV_ROUND_CLOSEST(freq, s->sampling_rate * bps) - 1; + + switch (s->cfg->scbrr_algo_id) { case SCBRR_ALGO_1: return freq / (16 * bps); case SCBRR_ALGO_2: @@ -1843,12 +1847,11 @@ static void sci_set_termios(struct uart_port *port, struct ktermios *termios, baud = uart_get_baud_rate(port, termios, old, 0, max_baud); if (likely(baud && port->uartclk)) { - if (s->cfg->scbrr_algo_id == SCBRR_ALGO_6) { + if (s->cfg->type == PORT_HSCIF) { sci_baud_calc_hscif(baud, port->uartclk, &t, &srr, &cks); } else { - t = sci_scbrr_calc(s->cfg->scbrr_algo_id, baud, - port->uartclk); + t = sci_scbrr_calc(s, baud, port->uartclk); for (cks = 0; t >= 256 && cks <= 3; cks++) t >>= 2; } @@ -2092,6 +2095,7 @@ static int sci_init_single(struct platform_device *dev, { struct uart_port *port = &sci_port->port; const struct resource *res; + unsigned int sampling_rate; unsigned int i; int ret; @@ -2143,28 +2147,47 @@ static int sci_init_single(struct platform_device *dev, case PORT_SCIFB: port->fifosize = 256; sci_port->overrun_bit = 9; + sampling_rate = 16; break; case PORT_HSCIF: port->fifosize = 128; + sampling_rate = 0; sci_port->overrun_bit = 0; break; case PORT_SCIFA: port->fifosize = 64; sci_port->overrun_bit = 9; + sampling_rate = 16; break; case PORT_SCIF: port->fifosize = 16; - if (p->regtype == SCIx_SH7705_SCIF_REGTYPE) + if (p->regtype == SCIx_SH7705_SCIF_REGTYPE) { sci_port->overrun_bit = 9; - else + sampling_rate = 16; + } else { sci_port->overrun_bit = 0; + sampling_rate = 32; + } break; default: port->fifosize = 1; sci_port->overrun_bit = 5; + sampling_rate = 32; break; } + /* Set the sampling rate if the baud rate calculation algorithm isn't + * specified. + */ + if (p->scbrr_algo_id == SCBRR_ALGO_NONE) { + /* SCIFA on sh7723 and sh7724 need a custom sampling rate that + * doesn't match the SoC datasheet, this should be investigated. + * Let platform data override the sampling rate for now. + */ + sci_port->sampling_rate = p->sampling_rate ? p->sampling_rate + : sampling_rate; + } + if (!early) { sci_port->iclk = clk_get(&dev->dev, "sci_ick"); if (IS_ERR(sci_port->iclk)) { diff --git a/include/linux/serial_sci.h b/include/linux/serial_sci.h index e9c3021a37ae..af414e1895a5 100644 --- a/include/linux/serial_sci.h +++ b/include/linux/serial_sci.h @@ -11,6 +11,7 @@ #define SCIx_NOT_SUPPORTED (-1) enum { + SCBRR_ALGO_NONE, /* Compute sampling rate in the driver */ SCBRR_ALGO_1, /* clk / (16 * bps) */ SCBRR_ALGO_2, /* DIV_ROUND_CLOSEST(clk, 32 * bps) - 1 */ SCBRR_ALGO_3, /* clk / (8 * bps) */ @@ -134,6 +135,7 @@ struct plat_sci_port { upf_t flags; /* UPF_* flags */ unsigned long capabilities; /* Port features/capabilities */ + unsigned int sampling_rate; unsigned int scbrr_algo_id; /* SCBRR calculation algo */ unsigned int scscr; /* SCSCR initialization */ -- 2.20.1