user/imx: Add i.MX6UL/ULL.

Update #3869

user/bsps/arm/imx.rst

@@ -7,9 +7,10 @@ imx (NXP i.MX)
 ==============
 
 This BSP offers only one variant, the `imx7`.  This variant supports the i.MX
-7Dual processor.  The basic hardware initialization is not performed by the
+7Dual processor and the i.MX 6UL/ULL processor family (with slightly different
-BSP.  A boot loader with device tree support must be used to start the BSP,
+clock settings).  The basic hardware initialization is not performed by the BSP.
-e.g. U-Boot.
+A boot loader with device tree support must be used to start the BSP, e.g.
+U-Boot or barebox.
 
 Build Configuration Options
 ---------------------------
@@ -40,9 +41,30 @@ The following options are available at the configure command line.
 ``IMX_CCM_UART_HZ``
    The UART clock frequency in Hz (default is 24000000).
 
+``IMX_CCM_ECSPI_HZ``
+   The ECSPI clock frequency in Hz (default is 67500000).
+
 ``IMX_CCM_AHB_HZ``
    The AHB clock frequency in Hz (default is 135000000).
 
+``IMX_CCM_SDHCI_HZ``
+   The SDHCI clock frequency in Hz (default is 196363000).
+
+Clock settings for different boards
+-----------------------------------
+
+The default clock settings are targeted for an i.MX 7Dual evaluation board using
+U-Boot. Some other boards with different boot loaders need different settings:
+
+ * Phytec phyCORE-i.MX 6ULL (system on module) with MCIMX6Y2CVM08AB and a
+   barebox bootloader (version ``2019.01.0-bsp-yocto-i.mx6ul-pd19.1.0``):
+
+   * IMX_CCM_IPG_HZ=66000000
+   * IMX_CCM_UART_HZ=80000000
+   * IMX_CCM_AHB_HZ=66000000
+   * IMX_CCM_SDHCI_HZ=198000000
+   * IMX_CCM_ECSPI_HZ=60000000
+
 Boot via U-Boot
 ---------------
 
@@ -65,6 +87,14 @@ The ``loadfdt`` command may be not defined in your U-Boot environment.  Just
 replace it with the appropriate commands to load the device tree at
 ``${fdt_addr}``.
 
+Boot via barebox
+----------------
+
+The same command like for U-Boot can be used to generate an application image.
+In a default configuration barebox expects an fdt image called `oftree` and a
+kernel image called `zImage` in the root folder of the bootable medium (e.g. an
+SD card).
+
 Clock Driver
 ------------
 
@@ -133,6 +163,17 @@ system controls:
 A value of zero for the time or count disables the interrupt coalescing in the
 corresponding direction.
 
+On the Phytec phyCORE-i.MX 6ULL modules the PHY needs an initialization for the
+clock. A special PHY driver handles that (``ksz8091rnb``). Add it to your libbsd
+config like that:
+
+.. code-block:: c
+
+    #define RTEMS_BSD_CONFIG_BSP_CONFIG
+    #define RTEMS_BSD_CONFIG_INIT
+    SYSINIT_DRIVER_REFERENCE(ksz8091rnb, miibus);
+    #include <machine/rtems-bsd-config.h>
+
 MMC/SDCard Driver
 -----------------