Commit 92a05748 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Greg Kroah-Hartman
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serial: sh-sci: Add support for SCIFA/SCIFB variable sampling rates 



Add support for sparse variable sampling rates on SCIFA and SCIFB.
According to the datasheet, sampling rate 1/5 needs a small quirk to
avoid corrupting the first byte received.

This increases the range and accuracy of supported baud rates.
E.g. on r8a7791/koelsch:
  - Supports now 134, 150, and standard 500000-4000000 bps,
  - Perfect match for 134, 150, 500000, 1000000, 2000000, and 4000000
    bps,
  - Accuracy has increased for most standard bps values.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 69eee8e9

drivers/tty/serial/sh-sci.c

+27 −2
Original line number Diff line number Diff line
@@ -88,6 +88,10 @@ enum SCI_CLKS { 
#define SCI_SR(x)		BIT((x) - 1)

#define SCI_SR_RANGE(x, y)	GENMASK((y) - 1, (x) - 1)



#define SCI_SR_SCIFAB		SCI_SR(5) | SCI_SR(7) | SCI_SR(11) | \

				SCI_SR(13) | SCI_SR(16) | SCI_SR(17) | \

				SCI_SR(19) | SCI_SR(27)



#define min_sr(_port)		ffs((_port)->sampling_rate_mask)

#define max_sr(_port)		fls((_port)->sampling_rate_mask)
@@ -2179,6 +2183,17 @@ done: 
	uart_update_timeout(port, termios->c_cflag, baud);



	if (best_clk >= 0) {

		if (port->type == PORT_SCIFA || port->type == PORT_SCIFB)

			switch (srr + 1) {

			case 5:  smr_val |= SCSMR_SRC_5;  break;

			case 7:  smr_val |= SCSMR_SRC_7;  break;

			case 11: smr_val |= SCSMR_SRC_11; break;

			case 13: smr_val |= SCSMR_SRC_13; break;

			case 16: smr_val |= SCSMR_SRC_16; break;

			case 17: smr_val |= SCSMR_SRC_17; break;

			case 19: smr_val |= SCSMR_SRC_19; break;

			case 27: smr_val |= SCSMR_SRC_27; break;

			}

		smr_val |= cks;

		dev_dbg(port->dev,

			 "SCR 0x%x SMR 0x%x BRR %u CKS 0x%x DL %u SRR %u\n",
@@ -2227,6 +2242,16 @@ done: 
	scr_val |= s->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0);

	dev_dbg(port->dev, "SCSCR 0x%x\n", scr_val);

	serial_port_out(port, SCSCR, scr_val);

	if ((srr + 1 == 5) &&

	    (port->type == PORT_SCIFA || port->type == PORT_SCIFB)) {

		/*

		 * In asynchronous mode, when the sampling rate is 1/5, first

		 * received data may become invalid on some SCIFA and SCIFB.

		 * To avoid this problem wait more than 1 serial data time (1

		 * bit time x serial data number) after setting SCSCR.RE = 1.

		 */

		udelay(DIV_ROUND_UP(10 * 1000000, baud));

	}



#ifdef CONFIG_SERIAL_SH_SCI_DMA

	/*
@@ -2523,7 +2548,7 @@ static int sci_init_single(struct platform_device *dev, 
		port->fifosize = 256;

		sci_port->overrun_reg = SCxSR;

		sci_port->overrun_mask = SCIFA_ORER;

		sci_port->sampling_rate_mask = SCI_SR(16);

		sci_port->sampling_rate_mask = SCI_SR_SCIFAB;

		break;

	case PORT_HSCIF:

		port->fifosize = 128;
@@ -2535,7 +2560,7 @@ static int sci_init_single(struct platform_device *dev, 
		port->fifosize = 64;

		sci_port->overrun_reg = SCxSR;

		sci_port->overrun_mask = SCIFA_ORER;

		sci_port->sampling_rate_mask = SCI_SR(16);

		sci_port->sampling_rate_mask = SCI_SR_SCIFAB;

		break;

	case PORT_SCIF:

		port->fifosize = 16;

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