[PATCH v3 3/7] arm64: Add helpers for detecting AArch32 support at EL0

Suzuki K Poulose Suzuki.Poulose at arm.com
Thu Apr 14 09:46:08 PDT 2016

On 14/04/16 17:39, Will Deacon wrote:
> On Thu, Mar 31, 2016 at 06:27:31PM +0100, Suzuki K Poulose wrote:
>> Adds a helper to extract the support for AArch32 at EL0
>> Tested-by: Yury Norov <ynorov at caviumnetworks.com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose at arm.com>

>> +static inline bool id_aa64pfr0_32bit_el0(u64 pfr0)
>> +{
>> +	u32 val = cpuid_feature_extract_unsigned_field(pfr0, ID_AA64PFR0_EL0_SHIFT);
>> +
>> +	return val == ID_AA64PFR0_EL0_32BIT_64BIT;
> Should this be >=? What are the rules for this register?

This feature value is kind of "FTR_EXACT" where, we don't know what the relationship
of the values are. Here is the list of possible values :

0001	EL0 can be executed in AArch64 state only.
0010	EL0 can be executed in either AArch64 or AArch32 state.

All the other values are reserved. So I believe "==" is better check.


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