tree 09d104dbed9bf79b7e4d05a799e18cc9485836ff
parent 2b184dd85e1e4c68d6ea26efa65f9d439ce6b3f0
parent c946874b731df8d5cd03e7358d982a3589a4c642
author Tom Rini <trini@konsulko.com> 1623107524 -0400
committer Tom Rini <trini@konsulko.com> 1623107524 -0400

Merge branch '2021-06-07-arm-cache-cp15-improvements' into next

To quote the series author, Patrick Delaunay:

On STM32MP15x platform we can use OP-TEE, loaded in DDR in a region
protected by a firewall. This region is reserved in the device with
the "no-map" property as defined in the binding file
doc/device-tree-bindings/reserved-memory/reserved-memory.txt.

Sometime the platform boot failed in U-Boot on a Cortex A7 access to
this region (depending of the binary and the issue can change with compiler
version or with code alignment), then the firewall raise an error,
for example:

E/TC:0   tzc_it_handler:19 TZC permission failure
E/TC:0   dump_fail_filter:420 Permission violation on filter 0
E/TC:0   dump_fail_filter:425 Violation @0xde5c6bf0, non-secure privileged read,
         AXI ID 5c0
E/TC:0   Panic

After investigation, the forbidden access is a speculative request performed
by the Cortex A7 because all the DDR is mapped as MEMORY with CACHEABLE
property.

The issue is solved only when the region reserved by OP-TEE is no more
mapped in U-Boot as it is already done in Linux kernel.

Tested on DK2 board with OP-TEE 3.12 / TF-A 2.4:

With hard-coded address for OP-TEE reserved memory,
the error doesn't occur.

 void dram_bank_mmu_setup(int bank)
 {
 ....

    	for (i = start >> MMU_SECTION_SHIFT;
 	     i < (start >> MMU_SECTION_SHIFT) + (size >> MMU_SECTION_SHIFT);
 	     i++) {
 		option = DCACHE_DEFAULT_OPTION;
 		if (i >= 0xde0)
 			option = INVALID_ENTRY;
 		set_section_dcache(i, option);
 	}
 }

Just by modifying the test on 0xde0 to 0xdf0, the OP-TEE memory protected
by firewall is mapped cacheable and the error occurs.

I think that it can be a general issue for ARM architecture: the "no-map" tag
of reserved memory in device should be respected by U-Boot if firewall
is configured before U-Boot execution.

But I don't propose a generic solution in
arm/lib/cache-cp15.c:dram_bank_mmu_setup()
because the device tree parsing done in lmb_init_and_reserve() takes a
long time when it is executed without data cache.