Using 4.5.1 SDK
Because devmem2 is trying to use /dev/mem it requires ‘sudo devmem2 0x86000000 w 0xabba’ and it works as expected.
I tried with and without a modified Device Tree to set aside a memory region to use an external device over JTAG to access this memory area. Both failed.
The modified device tree has 3 new entries
my_memreserve: /memreserve/ 0x0000000086000000 0x0000000000200000;
.
.
.
my_device {
compatible = “test,my_device”;
memory-region = <&my_reserve>;
};
.
.
.
my_reserve: my_reserve@86000000 {
//compatible = “shared-dma-pool”;
compatible = “test,my_device”;
reg = <0 0x86000000 0 0x200000>;
no-map; // if set, /dev/mem cannot write it
linux,phandle = <0x1e2>; //Use next available ID
phandle = <0x1e2>;
};
From a running program the device tree works as expected.
The errors that appear in the serial terminal during a debugger read while system is running are:
[ 1038.576720] t19x-arm-smmu 12000000.iommu: SMMU0: Unexpected {global,context} fault, this could be serious
[ 1038.576965] t19x-arm-smmu 12000000.iommu: GFSR 0x00000002, GFSYNR0 0x00000000, GFSYNR1 0x00000000, GFSYNR2 0x00000000, fault_addr=0x86000000, sid=0(0x0 - Unassigned SID)
[ 1038.577486] t19x-arm-smmu 12000000.iommu: SMMU0: Unexpected {global,context} fault, this could be serious
[ 1038.577670] t19x-arm-smmu 12000000.iommu: GFSR 0x80000000, GFSYNR0 0x00000000, GFSYNR1 0x00000000, GFSYNR2 0x00000000, fault_addr=0x86000000, sid=0(0x0 - Unassigned SID)
[ 1038.578154] t19x-arm-smmu 12000000.iommu: SMMU0: Unexpected {global,context} fault, this could be serious
[ 1038.578325] t19x-arm-smmu 12000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000000, GFSYNR1 0x00000000, GFSYNR2 0x00000000, fault_addr=0x86000000, sid=0(0x0 - Unassigned SID)
[ 1038.578809] t19x-arm-smmu 12000000.iommu: SMMU0: Unexpected {global,context} fault, this could be serious
[ 1038.579091] t19x-arm-smmu 12000000.iommu: GFSR 0x80000002, GFSYNR0 0x00000000, GFSYNR1 0x00000000, GFSYNR2 0x00000000, fault_addr=0x86000000, sid=0(0x0 - Unassigned SID)
[ 1038.585274] mc-err: (255) csr_axiapr: EMEM address decode error
[ 1038.591233] mc-err: status = 0x20064082; addr = 0xffffffff00; hi_adr_reg=ff08
[ 1038.598578] mc-err: secure: yes, access-type: read