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SubjectRe: [LINUX PATCH v2 3/3] spi: spi-mem: Add support for Zynq QSPI controller
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On 01/04/19 1:29 PM, Naga Sureshkumar Relli wrote:
> +/**
> + * zynq_qspi_config_op - Configure QSPI controller for specified transfer
> + * @xqspi: Pointer to the zynq_qspi structure
> + * @qspi: Pointer to the spi_device structure
> + *
> + * Sets the operational mode of QSPI controller for the next QSPI transfer and
> + * sets the requested clock frequency.
> + *
> + * Return: 0 on success and -EINVAL on invalid input parameter
> + *
> + * Note: If the requested frequency is not an exact match with what can be
> + * obtained using the prescalar value, the driver sets the clock frequency which
> + * is lower than the requested frequency (maximum lower) for the transfer. If
> + * the requested frequency is higher or lower than that is supported by the QSPI
> + * controller the driver will set the highest or lowest frequency supported by
> + * controller.
> + */
> +static int zynq_qspi_config_op(struct zynq_qspi *xqspi, struct spi_device *spi)
> +{
> + u32 config_reg, baud_rate_val = 0;
> +
> + /*
> + * Set the clock frequency
> + * The baud rate divisor is not a direct mapping to the value written
> + * into the configuration register (config_reg[5:3])
> + * i.e. 000 - divide by 2
> + * 001 - divide by 4
> + * ----------------
> + * 111 - divide by 256
> + */
> + while ((baud_rate_val < ZYNQ_QSPI_BAUD_DIV_MAX) &&
> + (clk_get_rate(xqspi->refclk) / (2 << baud_rate_val)) >
> + spi->max_speed_hz)
> + baud_rate_val++;
> +

Instead use DIV_ROUND_UP, something like below should work(untested):

unsigned long refclk_rate = clk_get_rate(xqspi->refclk);
u32 baud_rate_val = DIV_ROUND_UP(refclk_rate, spi->max_speed_hz) - 1;

if (baud_rate_val > ZYNQ_QSPI_BAUD_DIV_MAX)
baud_rate_val = ZYNQ_QSPI_BAUD_DIV_MAX;

> + config_reg = zynq_qspi_read(xqspi, ZYNQ_QSPI_CONFIG_OFFSET);
> +
> + /* Set the QSPI clock phase and clock polarity */
> + config_reg &= (~ZYNQ_QSPI_CONFIG_CPHA_MASK) &
> + (~ZYNQ_QSPI_CONFIG_CPOL_MASK);
> + if (spi->mode & SPI_CPHA)
> + config_reg |= ZYNQ_QSPI_CONFIG_CPHA_MASK;
> + if (spi->mode & SPI_CPOL)
> + config_reg |= ZYNQ_QSPI_CONFIG_CPOL_MASK;
> +
> + config_reg &= ~ZYNQ_QSPI_CONFIG_BDRATE_MASK;
> + config_reg |= (baud_rate_val << ZYNQ_QSPI_BAUD_DIV_SHIFT);
> + zynq_qspi_write(xqspi, ZYNQ_QSPI_CONFIG_OFFSET, config_reg);
> +
> + return 0;
> +}
> +

--
Regards
Vignesh

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