diff options
| author | Geert Uytterhoeven <geert+renesas@glider.be> | 2014-05-22 20:07:35 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@linaro.org> | 2014-05-26 14:30:37 +0100 |
| commit | 3beb61dbfcf188399cbc36ce1eeb8b2ba724de38 (patch) | |
| tree | 03a8a90b71a75dfc60b468fc541d59731b92470a /drivers/spi/spi-rspi.c | |
| parent | c9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff) | |
| download | lwn-3beb61dbfcf188399cbc36ce1eeb8b2ba724de38.tar.gz lwn-3beb61dbfcf188399cbc36ce1eeb8b2ba724de38.zip | |
spi: rspi: Round up division to avoid slave overclocking
The calculation of the bit rate divider used a standard C division, which
rounds down the quotient. This may lead to a higher bitrate than requested.
Round up to avoid this.
E.g. on Koelsch, the SPI flash (configured for 30 MHz) was driven at 48.75
MHz. After this patch it's driven at a safe 24.375 MHz.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>
Diffstat (limited to 'drivers/spi/spi-rspi.c')
| -rw-r--r-- | drivers/spi/spi-rspi.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/spi/spi-rspi.c b/drivers/spi/spi-rspi.c index 1fb0ad213324..5639f9529e0b 100644 --- a/drivers/spi/spi-rspi.c +++ b/drivers/spi/spi-rspi.c @@ -266,7 +266,8 @@ static int rspi_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); /* Sets transfer bit rate */ - spbr = clk_get_rate(rspi->clk) / (2 * rspi->max_speed_hz) - 1; + spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), + 2 * rspi->max_speed_hz) - 1; rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); /* Disable dummy transmission, set 16-bit word access, 1 frame */ @@ -302,7 +303,8 @@ static int rspi_rz_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); /* Sets transfer bit rate */ - spbr = clk_get_rate(rspi->clk) / (2 * rspi->max_speed_hz) - 1; + spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), + 2 * rspi->max_speed_hz) - 1; rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); /* Disable dummy transmission, set byte access */ @@ -335,7 +337,7 @@ static int qspi_set_config_register(struct rspi_data *rspi, int access_size) rspi_write8(rspi, rspi->sppcr, RSPI_SPPCR); /* Sets transfer bit rate */ - spbr = clk_get_rate(rspi->clk) / (2 * rspi->max_speed_hz); + spbr = DIV_ROUND_UP(clk_get_rate(rspi->clk), 2 * rspi->max_speed_hz); rspi_write8(rspi, clamp(spbr, 0, 255), RSPI_SPBR); /* Disable dummy transmission, set byte access */ |