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| author | Kamal Dasu <kdasu.kdev@gmail.com> | 2021-11-24 14:33:52 -0500 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2021-11-25 11:54:36 +0000 |
| commit | c74526f947ab946273939757c72499c0a5b09826 (patch) | |
| tree | d56815d604638deb69fdaa5fdcab81721d87de41 /drivers/spi/spi-bcm-qspi.c | |
| parent | b79332ef9d61513d0ccda74a5161bb7c31851e9c (diff) | |
| download | lwn-c74526f947ab946273939757c72499c0a5b09826.tar.gz lwn-c74526f947ab946273939757c72499c0a5b09826.zip | |
spi: bcm-qspi: choose sysclk setting based on requested speed
Check requested speed for a given transfer before setting
27MHz or 108Mhz sysclk on SoCs that support both. This way
for baud rates below 212Khz we can use 27Mhz clock.
Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Link: https://lore.kernel.org/r/20211124193353.32311-2-kdasu.kdev@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-bcm-qspi.c')
| -rw-r--r-- | drivers/spi/spi-bcm-qspi.c | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/drivers/spi/spi-bcm-qspi.c b/drivers/spi/spi-bcm-qspi.c index f3de3305d0f5..38e6e2cb62ca 100644 --- a/drivers/spi/spi-bcm-qspi.c +++ b/drivers/spi/spi-bcm-qspi.c @@ -287,6 +287,18 @@ static inline int bcm_qspi_spbr_min(struct bcm_qspi *qspi) return 8; } +static u32 bcm_qspi_calc_spbr(u32 clk_speed_hz, + const struct bcm_qspi_parms *xp) +{ + u32 spbr = 0; + + /* SPBR = System Clock/(2 * SCK Baud Rate) */ + if (xp->speed_hz) + spbr = clk_speed_hz / (xp->speed_hz * 2); + + return spbr; +} + /* Read qspi controller register*/ static inline u32 bcm_qspi_read(struct bcm_qspi *qspi, enum base_type type, unsigned int offset) @@ -621,9 +633,17 @@ static void bcm_qspi_hw_set_parms(struct bcm_qspi *qspi, spcr |= MSPI_SPCR3_HALFDUPLEX | MSPI_SPCR3_HDOUTTYPE; if (bcm_qspi_has_sysclk_108(qspi)) { - /* SYSCLK_108 */ - spcr |= MSPI_SPCR3_SYSCLKSEL_108; - qspi->base_clk = MSPI_BASE_FREQ * 4; + /* check requested baud rate before moving to 108Mhz */ + spbr = bcm_qspi_calc_spbr(MSPI_BASE_FREQ * 4, xp); + if (spbr > QSPI_SPBR_MAX) { + /* use SYSCLK_27Mhz for slower baud rates */ + spcr &= ~MSPI_SPCR3_SYSCLKSEL_MASK; + qspi->base_clk = MSPI_BASE_FREQ; + } else { + /* SYSCLK_108Mhz */ + spcr |= MSPI_SPCR3_SYSCLKSEL_108; + qspi->base_clk = MSPI_BASE_FREQ * 4; + } } if (xp->bits_per_word > 16) { @@ -649,9 +669,9 @@ static void bcm_qspi_hw_set_parms(struct bcm_qspi *qspi, bcm_qspi_write(qspi, MSPI, MSPI_SPCR3, spcr); } - if (xp->speed_hz) - spbr = qspi->base_clk / (2 * xp->speed_hz); - + /* SCK Baud Rate = System Clock/(2 * SPBR) */ + qspi->max_speed_hz = qspi->base_clk / (bcm_qspi_spbr_min(qspi) * 2); + spbr = bcm_qspi_calc_spbr(qspi->base_clk, xp); spbr = clamp_val(spbr, bcm_qspi_spbr_min(qspi), QSPI_SPBR_MAX); bcm_qspi_write(qspi, MSPI, MSPI_SPCR0_LSB, spbr); |