Re: [PATCH 5/6] firmware: samsung: acpm: Add TMU protocol support

[Tudor Ambarus <tudor.ambarus@linaro.org>]

On 5/6/26 6:13 PM, Alexey Klimov wrote:
> On Wed May 6, 2026 at 12:39 PM BST, Tudor Ambarus wrote:
>> The Thermal Management Unit (TMU) on the Google GS101 SoC is managed
>> through a hybrid model shared between the kernel and the Alive Clock
>> and Power Manager (ACPM) firmware.
>>
>> Add the protocol helpers required to communicate with the ACPM for
>> thermal operations, including initialization, threshold configuration,
>> temperature reading, and system suspend/resume handshakes.
>>
>> Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
>> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
>> ---
>>  drivers/firmware/samsung/Makefile                  |   1 +
>>  drivers/firmware/samsung/exynos-acpm-tmu.c         | 239 +++++++++++++++++++++
>>  drivers/firmware/samsung/exynos-acpm-tmu.h         |  28 +++
>>  drivers/firmware/samsung/exynos-acpm.c             |  12 ++
>>  .../linux/firmware/samsung/exynos-acpm-protocol.h  |  18 ++
>>  5 files changed, 298 insertions(+)
>>
>> diff --git a/drivers/firmware/samsung/Makefile b/drivers/firmware/samsung/Makefile
>> index 80d4f89b33a9..5a6f72bececf 100644
>> --- a/drivers/firmware/samsung/Makefile
>> +++ b/drivers/firmware/samsung/Makefile
>> @@ -3,4 +3,5 @@
>>  acpm-protocol-objs			:= exynos-acpm.o
>>  acpm-protocol-objs			+= exynos-acpm-pmic.o
>>  acpm-protocol-objs			+= exynos-acpm-dvfs.o
>> +acpm-protocol-objs			+= exynos-acpm-tmu.o
>>  obj-$(CONFIG_EXYNOS_ACPM_PROTOCOL)	+= acpm-protocol.o
>> diff --git a/drivers/firmware/samsung/exynos-acpm-tmu.c b/drivers/firmware/samsung/exynos-acpm-tmu.c
>> new file mode 100644
>> index 000000000000..c68d60b4c0b3
>> --- /dev/null
>> +++ b/drivers/firmware/samsung/exynos-acpm-tmu.c
> 
> [..]
> 
>> +static int acpm_tmu_to_linux_err(s8 fw_err)
>> +{
>> +	/*
>> +	 * ACPM_TMU_INIT uses BIT(0) and BIT(1) of msg.rx.ret to flag APM
>> +	 * capabilities. Treat zero and all positive values as success.
> 
> ACPM_TMU_INIT returns capabilities inside designated error field?

yes

> What about other messages/commands? They just return error code there?

all the other commands either return -1 for errors, regardless of the error
type, or 0 for success.
> 
>> +	 */
>> +	if (fw_err >= 0)
>> +		return 0;
>> +
>> +	if (fw_err == -1)
>> +		return -EACCES;
>> +
>> +	return -EIO;
>> +}
> 
> Could we map these return values with better granularity instead of
> returning -EIO for everything else that is not minus one?

I think we're good as we are now. The firmware returns either -1 for errors,
zero for success, or BIT(0) and BIT(1) for TMU_INIT to flag some capabilities.
I can't tell if there are other commands that return capabilities as well,
or if there are other capabilities for TMU_INIT, I don't have access to the
firmware code.

> 
> Is this error code convertation applies only to TMU protocol?

yes

Cheers,
ta