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authorGeert Uytterhoeven <geert+renesas@glider.be>2014-05-22 20:07:35 +0200
committerMark Brown <broonie@linaro.org>2014-05-26 14:30:37 +0100
commit3beb61dbfcf188399cbc36ce1eeb8b2ba724de38 (patch)
tree03a8a90b71a75dfc60b468fc541d59731b92470a /drivers/spi/spi-rspi.c
parentc9eaa447e77efe77b7fa4c953bd62de8297fd6c5 (diff)
downloadlinux-3beb61dbfcf188399cbc36ce1eeb8b2ba724de38.tar.bz2
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.c8
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 */