Unverified Commit 6a195f24 authored by Geert Uytterhoeven's avatar Geert Uytterhoeven Committed by Mark Brown
Browse files

spi: rspi: Increase bit rate range for QSPI 



Increase bit rate range for QSPI by extending the range of supported
dividers:
  1. QSPI supports a divider of 1, by setting SPBR to zero, increasing
     the upper limit from 48.75 to 97.5 MHz on R-Car Gen2,
  2. Make use of the Bit Rate Frequency Division Setting field in
     Command Registers, to decrease the lower limit from 191 to 24 kbps
     on R-Car Gen2.

Signed-off-by: default avatarGeert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200819125904.20938-6-geert+renesas@glider.be


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 4e71d926

drivers/spi/spi-rspi.c

+15 −3
Original line number Diff line number Diff line
@@ -334,14 +334,26 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size) 
 */

static int qspi_set_config_register(struct rspi_data *rspi, int access_size)

{

	int spbr;

	unsigned long clksrc;

	int brdv = 0, spbr;



	/* Sets output mode, MOSI signal, and (optionally) loopback */

	rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);



	/* Sets transfer bit rate */

	spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz);

	rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);

	clksrc = clk_get_rate(rspi->clk);

	if (rspi->speed_hz >= clksrc) {

		spbr = 0;

	} else {

		spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz);

		while (spbr > 255 && brdv < 3) {

			brdv++;

			spbr = DIV_ROUND_UP(spbr, 2);

		}

		spbr = clamp(spbr, 0, 255);

	}

	rspi_write8(rspi, spbr, RSPI_SPBR);

	rspi->spcmd |= SPCMD_BRDV(brdv);



	/* Disable dummy transmission, set byte access */

	rspi_write8(rspi, 0, RSPI_SPDCR);