Add clock_configure_mhz

Trades off accuracy (only gets to +/- 1MHz) for reduced code size as it doesn't need 64 bit division

Author: will-v-pi

src/rp2_common/hardware_clocks/clocks.c

@@ -123,6 +123,20 @@ bool clock_configure(clock_handle_t clock, uint32_t src, uint32_t auxsrc, uint32
     return true;
 }
 
+bool clock_configure_mhz(clock_handle_t clock, uint32_t src, uint32_t auxsrc, uint16_t src_freq_mhz, uint16_t freq_mhz) {
+    assert(src_freq_mhz >= freq_mhz);
+
+    if (freq_mhz > src_freq_mhz)
+        return false;
+
+    uint32_t div = (uint32_t)((((uint32_t) src_freq_mhz) << CLOCKS_CLK_GPOUT0_DIV_INT_LSB) / freq_mhz);
+    uint32_t actual_freq = (uint32_t) ((((uint32_t) src_freq_mhz) << CLOCKS_CLK_GPOUT0_DIV_INT_LSB) / div) * MHZ;
+
+    clock_configure_internal(clock, src, auxsrc, actual_freq, div);
+    // Store the configured frequency
+    return true;
+}
+
 void clock_configure_int_divider(clock_handle_t clock, uint32_t src, uint32_t auxsrc, uint32_t src_freq, uint32_t int_divider) {
     clock_configure_internal(clock, src, auxsrc, src_freq / int_divider, int_divider << CLOCKS_CLK_GPOUT0_DIV_INT_LSB);
 }

src/rp2_common/hardware_clocks/include/hardware/clocks.h

@@ -318,6 +318,22 @@ typedef clock_num_t clock_handle_t;
  */
 bool clock_configure(clock_handle_t clock, uint32_t src, uint32_t auxsrc, uint32_t src_freq, uint32_t freq);
 
+/*! \brief Configure the specified clock to +/- 1MHz
+ *  \ingroup hardware_clocks
+ *
+ * This function differs from clock_configure in that it does not configure the clocks as accurately,
+ * but therefore doesn't need to bring in 64-bit division functions, reducing the code size.
+ *
+ * See the tables in the description for details on the possible values for clock sources.
+ *
+ * \param clock The clock to configure
+ * \param src The main clock source, can be 0.
+ * \param auxsrc The auxiliary clock source, which depends on which clock is being set. Can be 0
+ * \param src_freq_mhz Frequency of the input clock source in MHz
+ * \param freq_mhz Requested frequency in MHz
+ */
+bool clock_configure_mhz(clock_handle_t clock, uint32_t src, uint32_t auxsrc, uint16_t src_freq_mhz, uint16_t freq_mhz);
+
 /*! \brief Configure the specified clock to use the undivided input source
  *  \ingroup hardware_clocks
  *