spi_setup(): add bps paramter

Signed-off-by: surenyi <surenyi82@163.com>

lib/spi.c

@@ -16,14 +16,29 @@ struct spi_descr {
     void           (*setup)(struct spi_descr *);
 };
 
-int spi_setup(spi_t spi, uint32_t cs, int mode)
+/* query APB1 clocks */
+static uint32_t __PCLK1()
 {
+    RCC_ClocksTypeDef clks;
+
+    RCC_GetClocksFreq(&clks);
+
+    return clks.PCLK1_Frequency;
+}
+
+int spi_setup(spi_t spi, uint32_t cs, int mode, int bps)
+{
+    uint32_t clk;
+    uint16_t prescale = SPI_BaudRatePrescaler_4;
+
     if (spi->setup)
         spi->setup(spi);
 
     spi->cs = cs;
-    gpio_init(spi->cs, GPIO_OUTPUT | GPIO_FLAG_PD | GPIO_FLAG_PU | GPIO_SPEED_FAST);
-    gpio_set(spi->cs);
+    if (cs > 0) {
+        gpio_init(spi->cs, GPIO_OUTPUT | GPIO_FLAG_PD | GPIO_FLAG_PU | GPIO_SPEED_FAST);
+        gpio_set(spi->cs);
+    }
 
     switch (spi->apb) {
         case 1:
@@ -36,9 +51,33 @@ int spi_setup(spi_t spi, uint32_t cs, int mode)
 
     SPI_DeInit(spi->base);
 
+
     SPI_StructInit(&spi->conf);
     spi->conf.SPI_Mode = SPI_Mode_Master;
-    spi->conf.SPI_BaudRatePrescaler = SPI_BaudRatePrescaler_4;
+
+    if (bps > 0) {
+        clk = __PCLK1();
+
+        if (bps >= (clk / 2)) {
+            prescale = SPI_BaudRatePrescaler_2;
+        } else if ((bps >= (clk / 4)) && (bps < (clk / 2))) {
+            prescale = SPI_BaudRatePrescaler_4;
+        } else if ((bps >= (clk / 8)) && (bps < (clk / 4))) {
+            prescale = SPI_BaudRatePrescaler_8;
+        } else if ((bps >= (clk / 16)) && (bps < (clk / 8))) {
+            prescale = SPI_BaudRatePrescaler_16;
+        } else if ((bps >= (clk / 32)) && (bps < (clk / 16))) {
+            prescale = SPI_BaudRatePrescaler_32;
+        } else if ((bps >= (clk / 64)) && (bps < (clk / 32))) {
+            prescale = SPI_BaudRatePrescaler_64;
+        } else if ((bps >= (clk / 128)) && (bps < (clk / 64))) {
+            prescale = SPI_BaudRatePrescaler_128;
+        } else if (bps < (clk / 128)) {
+            prescale = SPI_BaudRatePrescaler_256;
+        }
+    }
+
+    spi->conf.SPI_BaudRatePrescaler = prescale;
 
     if (mode & 0x1) {
         spi->conf.SPI_CPHA = SPI_CPHA_2Edge;

lib/spi.h

@@ -16,7 +16,7 @@ typedef struct spi_descr *spi_t;
 #define SPI_CS_LOW  (0)
 #define SPI_CS_HIGH (1)
 
-int spi_setup(spi_t, uint32_t cs, int mode);
+int spi_setup(spi_t, uint32_t cs, int mode, int bps);
 
 void spi_close(spi_t spi);
 void spi_set_mode(spi_t, int mode);