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driver: rng: Do not check ARM_SMCCC_TRNG_VERSION

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As described in the document SMC Calling Convention (ARM DEN 0028 1.5 F),
section 7 "Arm Architecture Calls", the SMC call SMCCC_ARCH_FEATURES is
not expected to support the function ID ARM_SMCCC_TRNG_VERSION. Trusted
Firmware-A follows up the specification in its implementation.

This commit removes the invocation to avoid the failure - which is a
wrong calling in U-boot. The later code invokes ARM_SMCCC_TRNG_VERSION
for retrieving the TRNG version, except it can read back the version
number, it also can be used to detect whether the TRNG is supported or
not.

Signed-off-by: Leo Yan <leo.yan@arm.com>
Reviewed-by: Weizhao Ouyang <o451686892@gmail.com>
This commit is contained in:
Leo Yan 2024-07-09 17:23:09 +01:00 • committed by Tom Rini
parent f6503fad0c
commit 51ebe8cd6a
1 changed files with 0 additions and 4 deletions
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4
drivers/rng/smccc_trng.c
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@ -135,10 +135,6 @@ static bool smccc_trng_is_supported(void (*invoke_fn)(unsigned long a0, unsigned
{
struct arm_smccc_res res;
(*invoke_fn)(ARM_SMCCC_ARCH_FEATURES, ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, &res);
if (res.a0 == ARM_SMCCC_RET_NOT_SUPPORTED)
return false;
(*invoke_fn)(ARM_SMCCC_TRNG_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
if (res.a0 & BIT(31))
return false;