On 22/03/2021 13:58, Richard Gong wrote:
>
>
> On 3/22/21 3:26 AM, Krzysztof Kozlowski wrote:
>>
>> On 21/03/2021 22:09, Arnd Bergmann wrote:
>>> On Sun, Mar 21, 2021 at 7:46 PM Krzysztof Kozlowski
>>> <krzysztof.kozlow...@canonical.com> wrote:
>>>>
>>>> The Stratix10 service layer and RCU drivers are useful only on
>>>> Stratix10, so on ARMv8. Compile testing the RCU driver on 32-bit ARM
>>>> fails:
>>>>
>>>> drivers/firmware/stratix10-rsu.c: In function 'rsu_status_callback':
>>>> include/linux/compiler_types.h:320:38: error: call to
>>>> '__compiletime_assert_179'
>>>> declared with attribute error: FIELD_GET: type of reg too small for
>>>> mask
>>>> _compiletime_assert(condition, msg, __compiletime_assert_,
>>>> __COUNTER__)
>>>> ...
>>>> drivers/firmware/stratix10-rsu.c:96:26: note: in expansion of macro
>>>> 'FIELD_GET'
>>>> priv->status.version = FIELD_GET(RSU_VERSION_MASK,
>>>>
>>>> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlow...@canonical.com>
>>>> Reported-by: kernel test robot <l...@intel.com>
>>>
>>> While I agree that one shouldn't run 32-bit kernels on this, we should also
>>> try
>>> to write drivers portably, and in theory any SoC that can run a 64-bit
>>> Arm kernel
>>> should also be able to run a 32-bit kernel if you include the same drivers.
>>>
>>> It seems that the problem here is in the smccc definition
>>>
>>> struct arm_smccc_res {
>>> unsigned long a0;
>>> unsigned long a1;
>>> unsigned long a2;
>>> unsigned long a3;
>>> };
>>>
>>> so the result of
>>>
>>> #define RSU_VERSION_MASK GENMASK_ULL(63, 32)
>>> priv->status.version = FIELD_GET(RSU_VERSION_MASK, res->a2);
>>>
>>> tries to access bits that are just not returned by the firmware here,
>>> which indicates that it probably won't work in this case.
>>>
>>> What I'm not entirely sure about is whether this is a problem in
>>> the Intel firmware implementation requiring the smccc caller to
>>> run in a 64-bit context, or if it's a mistake in the way the driver
>>> extracts the information if the firmware can actually pass it down
>>> correctly.
>>
>> The SMC has two calling conventions - SMC32/HVC32 and SMC64/HVC64. The
>> Stratix 10 driver uses the 64-bit calling convention (see
>> INTEL_SIP_SMC_FAST_CALL_VAL in
>> include/linux/firmware/intel/stratix10-smc.h), so it should not run in
>> aarch32 (regardless of type of hardware).
>>
>> I think that my patch limiting the support to 64-bit makes sense.
>>
>
> The stratix10 service layer and RSU driver are only used in Intel 64-bit
> SoCFPGA platforms.
This we know, however the questions were:
1. Why the driver cannot be made portable? Why it cannot be developed in
a way it allows building on different platforms?
2. Does the actual firmware support 32-bit SMC convention call?
Best regards,
Krzysztof
