On Mon, Sep 1, 2014 at 9:01 AM, <[email protected]> wrote:
> From: Greg Ungerer <[email protected]>
>
> The Armada SoC family implementation of this SPI hardware module has
> extended the configuration register to allow for a wider range of SPI
> clock rates. Specifically the Serial Baud Rate Pre-selection bits in the
> SPI Interface Configuration Register now also use bits 6 and 7 as well.
>
> Modify the baud rate calculation to handle these differences for the
> Armada case. Potentially a baud rate can be setup using a number of
> different pre-scalar and scalar combinations. This code tries all
> possible pre-scalar divisors (8 in total) to try and find the most
> accuate set.
>
> Signed-off-by: Greg Ungerer <[email protected]>
> ---
> drivers/spi/spi-orion.c | 77
> +++++++++++++++++++++++++++++++++++++++----------
> 1 file changed, 61 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/spi/spi-orion.c b/drivers/spi/spi-orion.c
> index c4675fa..816822f 100644
> --- a/drivers/spi/spi-orion.c
> +++ b/drivers/spi/spi-orion.c
> @@ -40,6 +40,7 @@
> #define ORION_SPI_MODE_CPHA (1 << 12)
> #define ORION_SPI_IF_8_16_BIT_MODE (1 << 5)
> #define ORION_SPI_CLK_PRESCALE_MASK 0x1F
> +#define ARMADA_SPI_CLK_PRESCALE_MASK 0xDF
> #define ORION_SPI_MODE_MASK (ORION_SPI_MODE_CPOL | \
> ORION_SPI_MODE_CPHA)
>
> @@ -82,31 +83,74 @@ static int orion_spi_baudrate_set(struct spi_device *spi,
> unsigned int speed)
> u32 rate;
> u32 prescale;
> u32 reg;
> + u32 mask;
> struct orion_spi *orion_spi;
>
> orion_spi = spi_master_get_devdata(spi->master);
>
> tclk_hz = clk_get_rate(orion_spi->clk);
>
> - /*
> - * the supported rates are: 4,6,8...30
> - * round up as we look for equal or less speed
> - */
> - rate = DIV_ROUND_UP(tclk_hz, speed);
> - rate = roundup(rate, 2);
> + if (of_machine_is_compatible("marvell,armada370")) {
This is ugly, can't you use a new compatible name for the driver (e.g.
"marvell,armada370-spi")? And then just store the result in orion_spi.
I don't think checking a compatible string for every transfer is good
for performance. Also what about armada370-xp, armada375, armada380
and any other variants out there?
> + unsigned int clk, spr, sppr, sppr2, err;
> + unsigned int best_spr, best_sppr, best_err;
>
> - /* check if requested speed is too small */
> - if (rate > 30)
> - return -EINVAL;
> + best_err = speed;
> + best_spr = 0;
> + best_sppr = 0;
>
> - if (rate < 4)
> - rate = 4;
> + tclk_hz *= 10;
> + if (speed > tclk_hz)
> + return -EINVAL;
>
> - /* Convert the rate to SPI clock divisor value. */
> - prescale = 0x10 + rate/2;
> + /* Iterate over the valid range looking for best fit */
> + for (sppr = 0; sppr < 8; sppr++) {
> + sppr2 = 0x1 << sppr;
> +
> + spr = tclk_hz / sppr2;
> + spr = DIV_ROUND_UP(spr, speed);
> + if ((spr == 0) || (spr > 15))
> + continue;
> +
> + clk = tclk_hz / (spr * sppr2);
> + err = speed - clk;
> +
> + if (err < best_err) {
> + best_spr = spr;
> + best_sppr = sppr;
> + best_err = err;
> + }
> + }
> +
> + if ((best_sppr == 0) && (best_spr == 0))
> + return -EINVAL;
> +
> + prescale = ((best_sppr & 0x6) << 5) |
> + ((best_sppr & 0x1) << 4) | best_spr;
> +
> + mask = ARMADA_SPI_CLK_PRESCALE_MASK;
> + } else {
> + mask = ORION_SPI_CLK_PRESCALE_MASK;
> +
> + /*
> + * the supported rates are: 4,6,8...30
> + * round up as we look for equal or less speed
> + */
> + rate = DIV_ROUND_UP(tclk_hz, speed);
> + rate = roundup(rate, 2);
> +
> + /* check if requested speed is too small */
> + if (rate > 30)
> + return -EINVAL;
> +
> + if (rate < 4)
> + rate = 4;
> +
> + /* Convert the rate to SPI clock divisor value. */
> + prescale = 0x10 + rate/2;
> + }
>
> reg = readl(spi_reg(orion_spi, ORION_SPI_IF_CONFIG_REG));
> - reg = ((reg & ~ORION_SPI_CLK_PRESCALE_MASK) | prescale);
> + reg = ((reg & ~mask) | prescale);
> writel(reg, spi_reg(orion_spi, ORION_SPI_IF_CONFIG_REG));
>
> return 0;
> @@ -348,7 +392,7 @@ static int orion_spi_probe(struct platform_device *pdev)
> struct orion_spi *spi;
> struct resource *r;
> unsigned long tclk_hz;
> - int status = 0;
> + int mindiv, status = 0;
>
> master = spi_alloc_master(&pdev->dev, sizeof(*spi));
> if (master == NULL) {
> @@ -390,7 +434,8 @@ static int orion_spi_probe(struct platform_device *pdev)
>
> tclk_hz = clk_get_rate(spi->clk);
> master->max_speed_hz = DIV_ROUND_UP(tclk_hz, 4);
> - master->min_speed_hz = DIV_ROUND_UP(tclk_hz, 30);
> + mindiv = (of_machine_is_compatible("marvell,armada370")) ? 1920 : 30;
Same as above.
Jonas
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