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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: Geert Uytterhoeven <geert+renesas@glider.be> Link: https://lore.kernel.org/r/20200819125904.20938-6-geert+renesas@glider.be Signed-off-by: Mark Brown <broonie@kernel.org>
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1 changed files with 15 additions and 3 deletions
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@ -334,14 +334,26 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size)
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*/
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static int qspi_set_config_register(struct rspi_data *rspi, int access_size)
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{
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int spbr;
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unsigned long clksrc;
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int brdv = 0, spbr;
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/* Sets output mode, MOSI signal, and (optionally) loopback */
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rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR);
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/* Sets transfer bit rate */
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spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->speed_hz);
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rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR);
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clksrc = clk_get_rate(rspi->clk);
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if (rspi->speed_hz >= clksrc) {
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spbr = 0;
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} else {
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spbr = DIV_ROUND_UP(clksrc, 2 * rspi->speed_hz);
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while (spbr > 255 && brdv < 3) {
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brdv++;
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spbr = DIV_ROUND_UP(spbr, 2);
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}
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spbr = clamp(spbr, 0, 255);
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}
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rspi_write8(rspi, spbr, RSPI_SPBR);
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rspi->spcmd |= SPCMD_BRDV(brdv);
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/* Disable dummy transmission, set byte access */
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rspi_write8(rspi, 0, RSPI_SPDCR);
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