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bsp/atsam: Fix handling of slow SPI speeds.

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This patch fixes an overflow in the frequency calculation of the SPI
driver for slow SPI speeds.
This commit is contained in:
Christian Mauderer
2018-08-09 08:37:38 +02:00
parent 71948f76fa
commit 8e6cfccf8c
1 changed files with 20 additions and 1 deletions
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bsps/arm/atsam/spi/atsam_spi_bus.c
+20 -1
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@@ -85,6 +85,23 @@ static uint8_t atsam_calculate_dlybcs(uint16_t delay_in_us)
(BOARD_MCK / delay_in_us) : 0xFF;
}
static uint32_t atsam_calculate_scbr(uint32_t speed_hz)
{
uint32_t scbr;
scbr = BOARD_MCK / speed_hz;
if (scbr > 0x0FF) {
/* Best estimation we can offer with the hardware. */
scbr = 0x0FF;
}
if (scbr == 0) {
/* SCBR = 0 isn't allowed. */
scbr = 1;
}
return scbr;
}
static void atsam_set_phase_and_polarity(uint32_t mode, uint32_t *csr)
{
uint32_t mode_mask = mode & SPI_MODE_3;
@@ -109,11 +126,13 @@ static void atsam_set_phase_and_polarity(uint32_t mode, uint32_t *csr)
static void atsam_configure_spi(atsam_spi_bus *bus)
{
uint8_t delay_cs;
uint32_t scbr;
uint32_t csr = 0;
uint32_t mode = 0;
uint32_t cs = bus->base.cs;
delay_cs = atsam_calculate_dlybcs(bus->base.delay_usecs);
scbr = atsam_calculate_scbr(bus->base.speed_hz);
mode |= SPI_MR_DLYBCS(delay_cs);
mode |= SPI_MR_MSTR;
@@ -137,7 +156,7 @@ static void atsam_configure_spi(atsam_spi_bus *bus)
csr =
SPI_DLYBCT(1000, BOARD_MCK) |
SPI_DLYBS(1000, BOARD_MCK) |
SPI_SCBR(bus->base.speed_hz, BOARD_MCK) |
SPI_CSR_SCBR(scbr) |
SPI_CSR_BITS(bus->base.bits_per_word - 8);
atsam_set_phase_and_polarity(bus->base.mode, &csr);