[PATCH 18/18] hw/riscv: microchip_pfsoc: Document the software used for testing

[Bin Meng]

From: Bin Meng <bin.meng@windriver.com>

Add some useful comments to document the software used for testing.
including how to patch HSS to bypass the DDR memory initialization,
HSS and Yocto BSP build instructions, etc.

To launch this machine for testing:
$ qemu-system-riscv64 -M microchip-icicle-kit -smp 5 \
    -bios path/to/hss.bin -sd path/to/sdcard.img \
    -nic user,model=cadence_gem \
    -nic tap,ifname=tap,model=cadence_gem \
    -display none -serial stdio \
    -chardev socket,id=serial1,path=serial1.sock,server,wait \
    -serial chardev:serial1

Signed-off-by: Bin Meng <bin.meng@windriver.com>

---

 hw/riscv/microchip_pfsoc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/riscv/microchip_pfsoc.c b/hw/riscv/microchip_pfsoc.c
index e8b7f86..1575fef 100644
--- a/hw/riscv/microchip_pfsoc.c
+++ b/hw/riscv/microchip_pfsoc.c
@@ -56,6 +56,27 @@
 /*
  * The BIOS image used by this machine is called Hart Software Services (HSS).
  * See https://github.com/polarfire-soc/hart-software-services
+ *
+ * As of now the DDR memory controller in the Microchip PolarFire SoC has not
+ * been modeled. Simply creating unimplemented devices does not make HSS happy.
+ * Emulating the DDR memory controller is tedious, so a patched HSS should be
+ * used as the BIOS for this machine.
+ *
+ * To patch HSS, open boards/icicle-kit-es/hss_board_init.c in the HSS source
+ * tree, find the boardInitFunctions[] array that contains the initialization
+ * routines for this board, and remove the line that contains 'HSS_DDRInit'.
+ *
+ * QEMU does not support eMMC hence the SD configuration shall be used in the
+ * HSS and Yocto BSP build. The eMMC configuration is not supported.
+ *
+ * Instructions to build HSS:
+ *   $ cp boards/icicle-kit-es/def_config.sdcard .config
+ *   $ make BOARD=icicle-kit-es
+ *
+ * For Yocto build, "MACHINE=icicle-kit-es-sd" should be specified, otherwise
+ * when booting Linux kernel the rootfs cannot be mounted. The generated image
+ * is something like: mpfs-dev-cli-icicle-kit-es-sd.rootfs.wic. Resize the file
+ * with 'qemu-image' to a power of 2 before passing to QEMU '-sd' command line.
  */
 #define BIOS_FILENAME   "hss.bin"
 #define RESET_VECTOR    0x20220000
-- 
2.7.4