riscv: Add support for SPI on Kendryte K210

This enables configs necessary for using SPI. The environment is saved to
the very end of SPI flash. This is unlikely to be overwritten unless the
entire flash is reprogrammed.

This also supplies a default bootcommand. It loads an image and device tree
from the first partition of the MMC. This is a minimal/least effort
bootcmd, so suggestions (especially in the form of patches) are welcome. I
didn't set up distro boot because I think it is unlikely that any
general-purpose linux distros will ever be ported to this board.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Tested-by: Chrstopher Obbard <obbardc@gmail.com>
Reviewed-by: Rick Chen <rick@andestech.com>

1 files changed, 267 insertions, 48 deletions

diff --git a/doc/board/sipeed/maix.rst b/doc/board/sipeed/maix.rst
index 92f2d112a9..bf945b3458 100644
--- a/doc/board/sipeed/maix.rst
+++ b/doc/board/sipeed/maix.rst
@@ -70,6 +70,7 @@ console shall be opened immediately. Boot output should look like the following:
     U-Boot 2020.04-rc2-00087-g2221cc09c1-dirty (Feb 28 2020 - 13:53:09 -0500)
 
     DRAM:  8 MiB
+    MMC:   spi@53000000:slot@0: 0
     In:    serial@38000000
     Out:   serial@38000000
     Err:   serial@38000000
@@ -118,14 +119,115 @@ The value of FW_PAYLOAD_OFFSET must match CONFIG_SYS_TEXT_BASE - 0x80000000.
 
 The file to flash is build/platform/kendryte/k210/firmware/fw_payload.bin.
 
+Booting
+^^^^^^^
+
+The default boot process is to load and boot the files ``/uImage`` and
+``/k210.dtb`` off of the first partition of the MMC. For Linux, this will result
+in an output like
+
+.. code-block:: none
+
+    U-Boot 2020.10-00691-gd1d651d988-dirty (Oct 16 2020 - 17:05:24 -0400)
+
+    DRAM:  8 MiB
+    MMC:   spi@53000000:slot@0: 0
+    Loading Environment from SPIFlash... SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
+    OK
+    In:    serial@38000000
+    Out:   serial@38000000
+    Err:   serial@38000000
+    Hit any key to stop autoboot:  0
+    1827380 bytes read in 1044 ms (1.7 MiB/s)
+    13428 bytes read in 10 ms (1.3 MiB/s)
+    ## Booting kernel from Legacy Image at 80060000 ...
+       Image Name:   linux
+       Image Type:   RISC-V Linux Kernel Image (uncompressed)
+       Data Size:    1827316 Bytes = 1.7 MiB
+       Load Address: 80000000
+       Entry Point:  80000000
+       Verifying Checksum ... OK
+    ## Flattened Device Tree blob at 80400000
+       Booting using the fdt blob at 0x80400000
+       Loading Kernel Image
+       Loading Device Tree to 00000000803f9000, end 00000000803ff473 ... OK
+
+    Starting kernel ...
+
+    [    0.000000] Linux version 5.9.0-00021-g6dcc2f0814c6-dirty (sean@godwin) (riscv64-linux-gnu-gcc (GCC) 10.2.0, GNU ld (GNU Binutils) 2.35) #34 SMP Fri Oct 16 14:40:57 EDT 2020
+    [    0.000000] earlycon: sifive0 at MMIO 0x0000000038000000 (options '115200n8')
+    [    0.000000] printk: bootconsole [sifive0] enabled
+    [    0.000000] Zone ranges:
+    [    0.000000]   DMA32    [mem 0x0000000080000000-0x00000000807fffff]
+    [    0.000000]   Normal   empty
+    [    0.000000] Movable zone start for each node
+    [    0.000000] Early memory node ranges
+    [    0.000000]   node   0: [mem 0x0000000080000000-0x00000000807fffff]
+    [    0.000000] Initmem setup node 0 [mem 0x0000000080000000-0x00000000807fffff]
+    [    0.000000] riscv: ISA extensions acdfgim
+    [    0.000000] riscv: ELF capabilities acdfim
+    [    0.000000] percpu: max_distance=0x18000 too large for vmalloc space 0x0
+    [    0.000000] percpu: Embedded 12 pages/cpu s18848 r0 d30304 u49152
+    [    0.000000] Built 1 zonelists, mobility grouping off.  Total pages: 2020
+    [    0.000000] Kernel command line: earlycon console=ttySIF0
+    [    0.000000] Dentry cache hash table entries: 1024 (order: 1, 8192 bytes, linear)
+    [    0.000000] Inode-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+    [    0.000000] Sorting __ex_table...
+    [    0.000000] mem auto-init: stack:off, heap alloc:off, heap free:off
+    [    0.000000] Memory: 6004K/8192K available (1139K kernel code, 126K rwdata, 198K rodata, 90K init, 81K bss, 2188K reserved, 0K cma-reserved)
+    [    0.000000] rcu: Hierarchical RCU implementation.
+    [    0.000000] rcu: RCU calculated value of scheduler-enlistment delay is 25 jiffies.
+    [    0.000000] NR_IRQS: 64, nr_irqs: 64, preallocated irqs: 0
+    [    0.000000] riscv-intc: 64 local interrupts mapped
+    [    0.000000] plic: interrupt-controller@C000000: mapped 65 interrupts with 2 handlers for 2 contexts.
+    [    0.000000] random: get_random_bytes called from 0x00000000800019a8 with crng_init=0
+    [    0.000000] k210-clk: clock-controller
+    [    0.000000] k210-clk: clock-controller: fixed-rate 26 MHz osc base clock
+    [    0.000000] clint: clint@2000000: timer running at 7800000 Hz
+    [    0.000000] clocksource: clint_clocksource: mask: 0xffffffffffffffff max_cycles: 0x3990be68b, max_idle_ns: 881590404272 ns
+    [    0.000014] sched_clock: 64 bits at 7MHz, resolution 128ns, wraps every 4398046511054ns
+    [    0.008450] Console: colour dummy device 80x25
+    [    0.012494] Calibrating delay loop (skipped), value calculated using timer frequency.. 15.60 BogoMIPS (lpj=31200)
+    [    0.022693] pid_max: default: 4096 minimum: 301
+    [    0.027352] Mount-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+    [    0.034428] Mountpoint-cache hash table entries: 512 (order: 0, 4096 bytes, linear)
+    [    0.045099] rcu: Hierarchical SRCU implementation.
+    [    0.050048] smp: Bringing up secondary CPUs ...
+    [    0.055417] smp: Brought up 1 node, 2 CPUs
+    [    0.059602] devtmpfs: initialized
+    [    0.082796] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 7645041785100000 ns
+    [    0.091820] futex hash table entries: 16 (order: -2, 1024 bytes, linear)
+    [    0.098507] pinctrl core: initialized pinctrl subsystem
+    [    0.140938] clocksource: Switched to clocksource clint_clocksource
+    [    0.247216] workingset: timestamp_bits=62 max_order=11 bucket_order=0
+    [    0.277392] k210-fpioa 502b0000.pinmux: K210 FPIOA pin controller
+    [    0.291724] k210-sysctl 50440000.syscon: K210 system controller
+    [    0.305317] k210-rst 50440000.syscon:reset-controller: K210 reset controller
+    [    0.313808] 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 115200) is a SiFive UART v0
+    [    0.322712] printk: console [ttySIF0] enabled
+    [    0.322712] printk: console [ttySIF0] enabled
+    [    0.331328] printk: bootconsole [sifive0] disabled
+    [    0.331328] printk: bootconsole [sifive0] disabled
+    [    0.353347] Freeing unused kernel memory: 88K
+    [    0.357004] This architecture does not have kernel memory protection.
+    [    0.363397] Run /init as init process
+
+Loading, Booting, and Storing Images
+------------------------------------
+
+.. _loading:
+
 Loading Images
 ^^^^^^^^^^^^^^
 
-To load a kernel, transfer it over serial.
+Serial
+""""""
+
+Use the ``loady`` command to load images over serial.
 
 .. code-block:: none
 
-    => loady 80000000 1500000
+    => loady $loadaddr 1500000
     ## Switch baudrate to 1500000 bps and press ENTER ...
 
     *** baud: 1500000
@@ -150,6 +252,61 @@ To load a kernel, transfer it over serial.
     *** baud: 115200 ***
     =>
 
+This command does not set ``$filesize``, so it may need to be set manually.
+
+SPI Flash
+"""""""""
+
+To load an image off of SPI flash, first set up a partition as described in
+:ref:`partitions`. Then, use ``mtd`` to load that partition
+
+.. code-block:: none
+
+    => sf probe
+    SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
+    => mtd read linux $loadaddr
+    Reading 2097152 byte(s) at offset 0x00000000
+
+This command does not set ``$filesize``, so it may need to be set manually.
+
+MMC
+"""
+
+The MMC device number is 0. To list partitions on the device, use ``part``:
+
+.. code-block:: none
+
+    => part list mmc 0
+
+    Partition Map for MMC device 0  --   Partition Type: EFI
+
+    Part    Start LBA       End LBA          Name
+            Attributes
+            Type GUID
+            Partition GUID
+      1     0x00000800      0x039effde      "boot"
+            attrs:  0x0000000000000000
+            type:   c12a7328-f81f-11d2-ba4b-00a0c93ec93b
+            guid:   96161f7d-7113-4cc7-9a24-08ab7fc5cb72
+
+To list files, use ``ls``:
+
+.. code-block:: none
+
+    => ls mmc 0:1
+    <DIR>       4096 .
+    <DIR>       4096 ..
+    <DIR>      16384 lost+found
+               13428 k210.dtb
+             1827380 uImage
+
+To load a file, use ``load``:
+
+.. code-block:: none
+
+    => load mmc 0:1 $loadaddr uImage
+    1827380 bytes read in 1049 ms (1.7 MiB/s)
+
 Running Programs
 ^^^^^^^^^^^^^^^^
 
@@ -160,20 +317,6 @@ To run a bare binary, use the ``go`` command:
 
 .. code-block:: none
 
-    => loady
-    ## Ready for binary (ymodem) download to 0x80000000 at 115200 bps...
-    C
-    *** file: ./examples/standalone/hello_world.bin
-    $ sz -vv ./examples/standalone/hello_world.bin
-    Sending: hello_world.bin
-    Bytes Sent:   4864   BPS:649
-    Sending:
-    Ymodem sectors/kbytes sent:   0/ 0k
-    Transfer complete
-
-    *** exit status: 0 ***
-    (CAN) packets, 5 retries
-    ## Total Size      = 0x000012f8 = 4856 Bytes
     => go 80000000
     ## Starting application at 0x80000000 ...
     Example expects ABI version 9
@@ -184,51 +327,127 @@ To run a bare binary, use the ``go`` command:
     argv[1] = "<NULL>"
     Hit any key to exit ...
 
+Note that this will only start a program on one hart. As-of this writing it is
+only possible to start a program on multiple harts using the ``bootm`` command.
+
 Legacy Images
 """""""""""""
 
-To run legacy images, use the ``bootm`` command:
+To create a legacy image, use ``tools/mkimage``:
 
 .. code-block:: none
 
-    $ tools/mkimage -A riscv -O u-boot -T standalone -C none -a 80000000 -e 80000000 -d examples/standalone/hello_world.bin hello_world.img
-    Image Name:
-    Created:      Thu Mar  5 12:04:10 2020
-    Image Type:   RISC-V U-Boot Standalone Program (uncompressed)
-    Data Size:    4856 Bytes = 4.74 KiB = 0.00 MiB
+    $ tools/mkimage -A riscv -O linux -T kernel -C none -a 0x80000000 -e 0x80000000 -n linux -d ../linux-git/arch/riscv/boot/Image uImage
+    Image Name:   linux
+    Created:      Fri Oct 16 17:36:32 2020
+    Image Type:   RISC-V Linux Kernel Image (uncompressed)
+    Data Size:    1827316 Bytes = 1784.49 KiB = 1.74 MiB
     Load Address: 80000000
     Entry Point:  80000000
 
-    $ picocom -b 115200 /dev/ttyUSB0
-    => loady
-    ## Ready for binary (ymodem) download to 0x80000000 at 115200 bps...
-    C
-    *** file: hello_world.img
-    $ sz -vv hello_world.img
-    Sending: hello_world.img
-    Bytes Sent:   4992   BPS:665
-    Sending:
-    Ymodem sectors/kbytes sent:   0/ 0k
-    Transfer complete
+The ``bootm`` command also requires an FDT, even if the image doesn't require
+one. After loading the image to ``$loadaddr`` and the FDT to ``$fdt_addr_r``,
+boot with:
 
-    *** exit status: 0 ***
-    CAN) packets, 3 retries
-    ## Total Size      = 0x00001338 = 4920 Bytes
-    => bootm
-    ## Booting kernel from Legacy Image at 80000000 ...
-       Image Name:
-       Image Type:   RISC-V U-Boot Standalone Program (uncompressed)
-       Data Size:    4856 Bytes = 4.7 KiB
+.. code-block:: none
+
+    => bootm $loadaddr - $fdt_addr_r
+    ## Booting kernel from Legacy Image at 80060000 ...
+       Image Name:   linux
+       Image Type:   RISC-V Linux Kernel Image (uncompressed)
+       Data Size:    1827316 Bytes = 1.7 MiB
        Load Address: 80000000
        Entry Point:  80000000
        Verifying Checksum ... OK
-       Loading Standalone Program
-    Example expects ABI version 9
-    Actual U-Boot ABI version 9
-    Hello World
-    argc = 0
-    argv[0] = "<NULL>"
-    Hit any key to exit ...
+    ## Flattened Device Tree blob at 80400000
+       Booting using the fdt blob at 0x80400000
+       Loading Kernel Image
+       Loading Device Tree to 00000000803f9000, end 00000000803ff473 ... OK
+
+    Starting kernel ...
+
+The FDT is verified after the kernel is relocated, so it must be loaded high
+enough so that it won't be overwritten. The default values for ``$loadaddr``
+and ``$fdt_addr_r`` should provide ample headroom for most use-cases.
+
+Flashing Images
+^^^^^^^^^^^^^^^
+
+SPI Flash
+"""""""""
+
+To flash data to SPI flash, first load it using one of the methods in
+:ref:`loading`. Addiotionally, create some partitions as described in
+:ref:`partitions`. Then use the ``mtd`` command:
+
+.. code-block:: none
+
+    => sf probe
+    SF: Detected w25q128fw with page size 256 Bytes, erase size 4 KiB, total 16 MiB
+    => mtd write linux $loadaddr 0 $filesize
+    Writing 2478162 byte(s) at offset 0x00000000
+
+Note that in order to write a bootable image, a header and tailer must be added.
+
+MMC
+"""
+
+MMC writes are unsupported for now.
+
+SPI Flash
+^^^^^^^^^
+
+Sipeed MAIX boards typically provide around 16 MiB of SPI NOR flash. U-Boot is
+stored in the first 1 MiB or so of this flash. U-Boot's environment is stored at
+the end of flash.
+
+.. _partitions:
+
+Partitions
+""""""""""
+
+There is no set data layout. The default partition layout only allocates
+partitions for U-Boot and its default environment
+
+.. code-block:: none
+
+    => mtd list
+    List of MTD devices:
+    * nor0
+      - type: NOR flash
+      - block size: 0x1000 bytes
+      - min I/O: 0x1 bytes
+      - 0x000000000000-0x000001000000 : "nor0"
+          - 0x000000000000-0x000000100000 : "u-boot"
+          - 0x000000fff000-0x000001000000 : "env"
+
+As an example, to allocate 2MiB for Linux and (almost) 13 MiB for other data,
+set the ``mtdparts`` like:
+
+.. code-block:: none
+
+    => env set mtdparts nor0:1M(u-boot),2M(linux),0xcff000(data),0x1000@0xfff000(env)
+    => mtd list
+    List of MTD devices:
+    * nor0
+      - type: NOR flash
+      - block size: 0x1000 bytes
+      - min I/O: 0x1 bytes
+      - 0x000000000000-0x000001000000 : "nor0"
+          - 0x000000000000-0x000000100000 : "u-boot"
+          - 0x000000100000-0x000000300000 : "linux"
+          - 0x000000300000-0x000000fff000 : "data"
+          - 0x000000fff000-0x000001000000 : "env"
+
+To make these changes permanent, save the environment:
+
+.. code-block:: none
+
+    => env save
+    Saving Environment to SPIFlash... Erasing SPI flash...Writing to SPI flash...done
+    OK
+
+U-Boot will always load the environment from the last 4 KiB of flash.
 
 Pin Assignment
 --------------