spi/mxs: Make the SPI block clock speed configurable via DT

Add "clock-frequency" property, which allows configuring the SPI block's
base speed.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

2 files changed, 19 insertions, 6 deletions

diff --git a/Documentation/devicetree/bindings/spi/mxs-spi.txt b/Documentation/devicetree/bindings/spi/mxs-spi.txt
index c36296f5ad28..e2e13957c2a4 100644
--- a/Documentation/devicetree/bindings/spi/mxs-spi.txt
+++ b/Documentation/devicetree/bindings/spi/mxs-spi.txt
@@ -6,6 +6,10 @@ Required properties:
 - interrupts: Should contain SSP interrupts (error irq first, dma irq second)
 - fsl,ssp-dma-channel: APBX DMA channel for the SSP
 
+Optional properties:
+- clock-frequency : Input clock frequency to the SPI block in Hz.
+                    Default is 160000000 Hz.
+
 Example:
 
 ssp0: ssp@80010000 {
diff --git a/drivers/spi/spi-mxs.c b/drivers/spi/spi-mxs.c
index 556e5ef907fa..edf1360ab09e 100644
--- a/drivers/spi/spi-mxs.c
+++ b/drivers/spi/spi-mxs.c
@@ -520,10 +520,17 @@ static int __devinit mxs_spi_probe(struct platform_device *pdev)
         struct pinctrl *pinctrl;
         struct clk *clk;
         void __iomem *base;
-        int devid, dma_channel;
+        int devid, dma_channel, clk_freq;
         int ret = 0, irq_err, irq_dma;
         dma_cap_mask_t mask;
 
+        /*
+         * Default clock speed for the SPI core. 160MHz seems to
+         * work reasonably well with most SPI flashes, so use this
+         * as a default. Override with "clock-frequency" DT prop.
+         */
+        const int clk_freq_default = 160000000;
+
         iores = platform_get_resource(pdev, IORESOURCE_MEM, 0);
         irq_err = platform_get_irq(pdev, 0);
         irq_dma = platform_get_irq(pdev, 1);
@@ -555,12 +562,18 @@ static int __devinit mxs_spi_probe(struct platform_device *pdev)
                                 "Failed to get DMA channel\n");
                         return -EINVAL;
                 }
+
+                ret = of_property_read_u32(np, "clock-frequency",
+                                           &clk_freq);
+                if (ret)
+                        clk_freq = clk_freq_default;
         } else {
                 dmares = platform_get_resource(pdev, IORESOURCE_DMA, 0);
                 if (!dmares)
                         return -EINVAL;
                 devid = pdev->id_entry->driver_data;
                 dma_channel = dmares->start;
+                clk_freq = clk_freq_default;
         }
 
         master = spi_alloc_master(&pdev->dev, sizeof(*spi));
@@ -598,12 +611,8 @@ static int __devinit mxs_spi_probe(struct platform_device *pdev)
                 goto out_master_free;
         }
 
-        /*
-         * Crank up the clock to 120MHz, this will be further divided onto a
-         * proper speed.
-         */
         clk_prepare_enable(ssp->clk);
-        clk_set_rate(ssp->clk, 120 * 1000 * 1000);
+        clk_set_rate(ssp->clk, clk_freq);
         ssp->clk_rate = clk_get_rate(ssp->clk) / 1000;
 
         stmp_reset_block(ssp->base);