spi: orion: support armada extended baud rates

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
accurate set.

This change introduces (and documents) a new device tree compatible
device name "armada-370-spi" to support this.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Tested-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Reviewed-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 94 insertions, 22 deletions

diff --git a/drivers/spi/spi-orion.c b/drivers/spi/spi-orion.c
index c4675fa8b645..acf8e48db16c 100644
--- a/drivers/spi/spi-orion.c
+++ b/drivers/spi/spi-orion.c
@@ -18,6 +18,7 @@
 #include <linux/module.h>
 #include <linux/pm_runtime.h>
 #include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/clk.h>
 #include <linux/sizes.h>
 #include <asm/unaligned.h>
@@ -40,13 +41,27 @@
 #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)
 
+enum orion_spi_type {
+        ORION_SPI,
+        ARMADA_SPI,
+};
+
+struct orion_spi_dev {
+        enum orion_spi_type     typ;
+        unsigned int            min_divisor;
+        unsigned int            max_divisor;
+        u32                     prescale_mask;
+};
+
 struct orion_spi {
         struct spi_master       *master;
         void __iomem            *base;
         struct clk              *clk;
+        const struct orion_spi_dev *devdata;
 };
 
 static inline void __iomem *spi_reg(struct orion_spi *orion_spi, u32 reg)
@@ -83,30 +98,66 @@ static int orion_spi_baudrate_set(struct spi_device *spi, unsigned int speed)
         u32 prescale;
         u32 reg;
         struct orion_spi *orion_spi;
+        const struct orion_spi_dev *devdata;
 
         orion_spi = spi_master_get_devdata(spi->master);
+        devdata = orion_spi->devdata;
 
         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 (devdata->typ == ARMADA_SPI) {
+                unsigned int clk, spr, sppr, sppr2, err;
+                unsigned int best_spr, best_sppr, best_err;
+
+                best_err = speed;
+                best_spr = 0;
+                best_sppr = 0;
+
+                /* 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;
 
-        /* check if requested speed is too small */
-        if (rate > 30)
-                return -EINVAL;
+                        clk = tclk_hz / (spr * sppr2);
+                        err = speed - clk;
 
-        if (rate < 4)
-                rate = 4;
+                        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;
+        } else {
+                /*
+                 * 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;
 
-        /* Convert the rate to SPI clock divisor value. */
-        prescale = 0x10 + rate/2;
+                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 & ~devdata->prescale_mask) | prescale);
         writel(reg, spi_reg(orion_spi, ORION_SPI_IF_CONFIG_REG));
 
         return 0;
@@ -342,8 +393,31 @@ static int orion_spi_reset(struct orion_spi *orion_spi)
         return 0;
 }
 
+static const struct orion_spi_dev orion_spi_dev_data = {
+        .typ = ORION_SPI,
+        .min_divisor = 4,
+        .max_divisor = 30,
+        .prescale_mask = ORION_SPI_CLK_PRESCALE_MASK,
+};
+
+static const struct orion_spi_dev armada_spi_dev_data = {
+        .typ = ARMADA_SPI,
+        .min_divisor = 1,
+        .max_divisor = 1920,
+        .prescale_mask = ARMADA_SPI_CLK_PRESCALE_MASK,
+};
+
+static const struct of_device_id orion_spi_of_match_table[] = {
+        { .compatible = "marvell,orion-spi", .data = &orion_spi_dev_data, },
+        { .compatible = "marvell,armada-370-spi", .data = &armada_spi_dev_data, },
+        {}
+};
+MODULE_DEVICE_TABLE(of, orion_spi_of_match_table);
+
 static int orion_spi_probe(struct platform_device *pdev)
 {
+        const struct of_device_id *of_id;
+        const struct orion_spi_dev *devdata;
         struct spi_master *master;
         struct orion_spi *spi;
         struct resource *r;
@@ -378,6 +452,10 @@ static int orion_spi_probe(struct platform_device *pdev)
         spi = spi_master_get_devdata(master);
         spi->master = master;
 
+        of_id = of_match_device(orion_spi_of_match_table, &pdev->dev);
+        devdata = of_id->data;
+        spi->devdata = devdata;
+
         spi->clk = devm_clk_get(&pdev->dev, NULL);
         if (IS_ERR(spi->clk)) {
                 status = PTR_ERR(spi->clk);
@@ -389,8 +467,8 @@ static int orion_spi_probe(struct platform_device *pdev)
                 goto out;
 
         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);
+        master->max_speed_hz = DIV_ROUND_UP(tclk_hz, devdata->min_divisor);
+        master->min_speed_hz = DIV_ROUND_UP(tclk_hz, devdata->max_divisor);
 
         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
         spi->base = devm_ioremap_resource(&pdev->dev, r);
@@ -469,12 +547,6 @@ static const struct dev_pm_ops orion_spi_pm_ops = {
                            NULL)
 };
 
-static const struct of_device_id orion_spi_of_match_table[] = {
-        { .compatible = "marvell,orion-spi", },
-        {}
-};
-MODULE_DEVICE_TABLE(of, orion_spi_of_match_table);
-
 static struct platform_driver orion_spi_driver = {
         .driver = {
                 .name   = DRIVER_NAME,