我正在使用双Cortex-A9处理器开发Altera的Cyclone V SOC FPGA。嵌入式系统（linux-socfpga 4.16）使用Buildroot-2018.05创建。
我在引导时使用“顶部”设备树作为处理器组件，并使用设备树覆盖来配置组件的FPGA部分并加载关联的驱动程序。叠加层将附加到顶部DT的base_fpga_region。
/dts-v1/;
/ {
model = "MY_PROJECT"; /* appended from boardinfo */
compatible = "altr,socfpga-cyclone5", "altr,socfpga"; /* appended from boardinfo */
#address-cells = <1>;
#size-cells = <1>;
cpus {
[...]
}; //end cpus
memory {
device_type = "memory";
reg = <0xffff0000 0x00010000>,
<0x00000000 0x80000000>;
}; //end memory
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
mem_dma_reserved {
compatible = "shared-dma-pool";
no-map;
reg = <0x78000000 0x8000000>;
};
};
soc: soc {
device_type = "soc";
ranges;
#address-cells = <1>;
#size-cells = <1>;
compatible = "altr,avalon", "simple-bus";
bus-frequency = <0>;
fpgabridge1: fpgabridge@1 {
compatible = "altr,socfpga-lwhps2fpga-bridge";
resets = <&hps_rstmgr 97>; /* appended from boardinfo */
clocks = <&l4_main_clk>; /* appended from boardinfo */
#address-cells = <1>;
#size-cells = <1>;
ranges;
bridge-enable = <1>;
label = "lwhps2fpga";
reset-names = "lwhps2fpga";
reg = <0xff200000 0x200000>;
reg-names = "axi_h2f_lw";
}; //end fpgabridge@1 (fpgabridge1)
base_fpga_region: base_fpga_region {
compatible = "fpga-region";
#address-cells = <0x2>;
#size-cells = <0x1>;
fpga-mgr = <&hps_fpgamgr>;
fpga-bridges = <&fpgabridge1>;
ranges = <0x0 0x0 0xff200000 0x200000>;
}; //end base_fpga_region (base_fpga_region)
etc......
/dts-v1/ /plugin/;
/{
fragment@0 {
target-path = "/soc/base_fpga_region";
#address-cells = <2>;
#size-cells = <1>;
__overlay__ {
#address-cells = <2>;
#size-cells = <1>;
firmware-name = "my_project.rbf";
my_dma_0: dma@0x000000000 {
compatible = "my_company,my_dma-0.1";
reg = <0x00000000 0x0000000 0x00000014>;
memory-region = <&mem_dma_reserved>;
}; //end dma@0x000000000 (my_dma_0)
};
};
};
我的问题是将顶部DT的mem_dma_reserved链接到叠加层中的memory-region。
我假设在使用-@选项将dts转换为dtbo时，覆盖层应该使用mem_dma_reserved选项获得__fixups__的虚拟空间。我已经创建了dtbo文件，并再次在dts中对其进行了转换，以查看编译过程中完成了什么：
dtc -@ -I dts -O dtb -o overlay.dtbo overlay.dts
dtc -I dtb -O dts -o overlay_recovery.dts overlay.dtbo
/dts-v1/;
/ {
fragment@0 {
target-path = "/soc/base_fpga_region";
#address-cells = <0x2>;
#size-cells = <0x1>;
__overlay__ {
#address-cells = <0x2>;
#size-cells = <0x1>;
firmware-name = "my_project.rbf";
dma@0x000000000 {
compatible = "my_company,my_dma-0.1";
reg = <0x0 0x0 0x14>;
memory-region = <0xffffffff>; // phandle converted to 0xffffffff, cannot resolve unless the __fixup__ function does it.
linux,phandle = <0x2>;
phandle = <0x2>;
};
};
};
__symbols__ {
my_dma_0 = "/fragment@0/__overlay__/dma@0x000000000";
};
__fixups__ {
mem_dma_reserved = "/fragment@0/__overlay__/dma@0x000000000:memory-region:0";
};
};
我们可以看到内存区域的模数是0xFFFFFFFF，因为覆盖不知道<＆mem_dma_reserved>节点。修复程序部分应该能够在加载时恢复原来的状态，但是它不起作用，并且出现此错误：
[27.434730] OF：解析程序：of_resolve_phandles：设备树的根目录中没有符号。
[27.440401] OF：解析器：叠加phandle修复失败：-22
[27.445993] create_overlay：无法解析树
我在DT顶部从dtb到dts进行了相同的再生。我已经看到，保留内存的虚拟内存实际上是0x6。我已经在设备树覆盖中编写了<0x6>而不是<＆mem_dma_reserved>，并且使用此配置，一切都加载了！
如何使覆盖图自动找到<＆mem_dma_reserved>而不用手工进行？
正如 ikwzm 所指出的那样，我在顶部设备树中添加了以下几行：
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
mem_dma_reserved: mem_dma_reserved { // add a label
compatible = "shared-dma-pool";
no-map;
reg = <0x78000000 0x8000000>;
};
};
[...]
// add the whole symbol block
__symbols__ {
mem_dma_reserved = "/reserved-memory/mem_dma_reserved ";
};
错误现在消失了，但是：
我希望在操作期间加载my_dma驱动程序。
我检查了设备树覆盖是否已被适当考虑：
ls / sys / firmware / devicetree / base / soc / base_fpga_region /
my_dma_0
other_stuff猫/ sys / firmware / devicetree / base / soc / base_fpga_region / my_dma_0 / memory-region
//什么都没有//
似乎没有附加存储区域。
我错过了什么？
答案 0 :(得分：2)
制作顶部dtb时，是否在dtc命令上附加了--symbol（或-@）选项？
按如下所示向mem_dma_reserved添加标签（符号）。
reserved-memory {
#address-cells = <1>;
#size-cells = <1>;
ranges;
mem_dma_reserved: mem_dma_reserved {
compatible = "shared-dma-pool";
no-map;
reg = <0x78000000 0x8000000>;
};
};
使用--symbol选项dtc命令创建dtb时，将按如下所示添加__symbols__{...};，并且应在其中找到mem_dma_reserved = "/reserved-memory/ mem_dma_reserved";。
__symbols__ {
:
:
:
mem_dma_reserved = "/reserved-memory/mem_dma_reserved";
usb_phy0 = "/phy0";
};