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spi: rspi: Increase bit rate range for RSPI on SH

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Increase bit rate range for RSPI on legacy SH by making use of the Bit
Rate Frequency Division Setting field in Command Registers, just like is
already done on RZ/A.  This decreases the lower limit by a factor of 8.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200819125904.20938-5-geert+renesas@glider.be
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Geert Uytterhoeven 2020-08-19 14:59:01 +02:00 committed by Mark Brown
parent feace90233
commit 4e71d926ab
No known key found for this signature in database
GPG key ID: 24D68B725D5487D0
1 changed files with 18 additions and 17 deletions
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35
drivers/spi/spi-rspi.c
View file

@ -248,19 +248,32 @@ struct spi_ops {
u8 num_hw_ss;
};
static void rspi_set_rate(struct rspi_data *rspi)
{
unsigned long clksrc;
int brdv = 0, spbr;
clksrc = clk_get_rate(rspi->clk);
spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1;
while (spbr > 255 && brdv < 3) {
brdv++;
spbr = DIV_ROUND_UP(spbr + 1, 2) - 1;
}
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
rspi->spcmd |= SPCMD_BRDV(brdv);
}
/*
* functions for RSPI on legacy SH
*/
static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
{
int 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) - 1;
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
rspi_set_rate(rspi);
/* Disable dummy transmission, set 16-bit word access, 1 frame */
rspi_write8(rspi, 0, RSPI_SPDCR);
@ -290,23 +303,11 @@ static int rspi_set_config_register(struct rspi_data *rspi, int access_size)
*/
static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size)
{
int spbr;
int brdv = 0;
unsigned long clksrc;
/* Sets output mode, MOSI signal, and (optionally) loopback */
rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
clksrc = clk_get_rate(rspi->clk);
spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz) - 1;
while (spbr > 255 && brdv < 3) {
brdv++;
spbr = DIV_ROUND_UP(spbr + 1, 2) - 1;
}
/* Sets transfer bit rate */
rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
rspi->spcmd |= SPCMD_BRDV(brdv);
rspi_set_rate(rspi);
/* Disable dummy transmission, set byte access */
rspi_write8(rspi, SPDCR_SPLBYTE, RSPI_SPDCR);