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| author | Paulo Zaneti <paulo.zaneti@datacom.ind.br> | 2016-10-29 11:02:19 +0200 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2016-10-29 20:00:19 +0200 |
| commit | 73aaf15849d9421fa696c3d7785952d8100042b2 (patch) | |
| tree | cf4d715eaa01cb504afb6afe5bf0d20e0070bfad /drivers/spi | |
| parent | spi: fsl-espi: small fix to error path in fsl_espi_irq (diff) | |
| download | linux-73aaf15849d9421fa696c3d7785952d8100042b2.tar.xz linux-73aaf15849d9421fa696c3d7785952d8100042b2.zip | |
spi: fsl-espi: fix support for all available clock rates
According to NXP ESPI datasheet, the SPI clock rate is:
spi_clk = System_Clock / ( 2 * DIV16 * ( 1 + PM ) )
Where System_Clock is the platform clock divided by 2,
DIV16 may be 1 or 16, and PM is a 4 bits integer (0 to 15).
Isolating PM on the expression, we get:
PM = (System_Clock / ( 2 * DIV16 * spi_clk ) ) - 1
Where System_Clock = mpc8xxx_spi->spibrg / 2, spi_clk = hz,
and DIV16 = 1 or DIV16 = 16. So,
PM = (mpc8xxx_spi->spibrg / ( 4 * hz) ) - 1
or
PM = (mpc8xxx_spi->spibrg / ( 16 * 4 * hz) ) - 1
Current spi-fsl-espi driver can't configure the HW for all
supported clock rates. It filters out clock rates for PM = 0
and PM = 1.
This patch allows all range of supported clock rates to be
configured on the ESPI controller.
Signed-off-by: Paulo Zaneti <paulo.zaneti@datacom.ind.br>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-fsl-espi.c | 28 |
1 files changed, 12 insertions, 16 deletions
diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c index 1d3c9023391d..8b3a28739d9a 100644 --- a/drivers/spi/spi-fsl-espi.c +++ b/drivers/spi/spi-fsl-espi.c @@ -247,8 +247,7 @@ static void fsl_espi_setup_transfer(struct spi_device *spi, { struct mpc8xxx_spi *mpc8xxx_spi = spi_master_get_devdata(spi->master); int bits_per_word = t ? t->bits_per_word : spi->bits_per_word; - u32 hz = t ? t->speed_hz : spi->max_speed_hz; - u8 pm; + u32 pm, hz = t ? t->speed_hz : spi->max_speed_hz; struct spi_mpc8xxx_cs *cs = spi->controller_state; /* mask out bits we are going to set */ @@ -256,22 +255,19 @@ static void fsl_espi_setup_transfer(struct spi_device *spi, cs->hw_mode |= CSMODE_LEN(bits_per_word - 1); - if ((mpc8xxx_spi->spibrg / hz) > 64) { + pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 4) - 1; + + if (pm > 15) { cs->hw_mode |= CSMODE_DIV16; - pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 16 * 4); - - WARN_ONCE(pm > 33, "%s: Requested speed is too low: %d Hz. " - "Will use %d Hz instead.\n", dev_name(&spi->dev), - hz, mpc8xxx_spi->spibrg / (4 * 16 * (32 + 1))); - if (pm > 33) - pm = 33; - } else { - pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 4); + pm = DIV_ROUND_UP(mpc8xxx_spi->spibrg, hz * 16 * 4) - 1; + + WARN_ONCE(pm > 15, + "%s: Requested speed is too low: %u Hz. Will use %u Hz instead.\n", + dev_name(&spi->dev), hz, + mpc8xxx_spi->spibrg / (4 * 16 * (15 + 1))); + if (pm > 15) + pm = 15; } - if (pm) - pm--; - if (pm < 2) - pm = 2; cs->hw_mode |= CSMODE_PM(pm); |