linux-kernel - Re: [PATCH v7 05/10] nvmem: qcom-spmi-sdam: Migrate to devm_spmi_subdevice_alloc_and

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <dd877ea8-b634-4cc9-8280-08663f82776d@oss.qualcomm.com>
Date: Wed, 14 Jan 2026 11:04:30 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
        jic23@...nel.org, dlechner@...libre.com, nuno.sa@...log.com,
        andy@...nel.org, arnd@...db.de, gregkh@...uxfoundation.org,
        srini@...nel.org, vkoul@...nel.org, neil.armstrong@...aro.org,
        sre@...nel.org, sboyd@...nel.org, krzk@...nel.org,
        dmitry.baryshkov@....qualcomm.com, quic_wcheng@...cinc.com,
        melody.olvera@....qualcomm.com, quic_nsekar@...cinc.com,
        ivo.ivanov.ivanov1@...il.com, abelvesa@...nel.org,
        luca.weiss@...rphone.com, mitltlatltl@...il.com,
        krishna.kurapati@....qualcomm.com, linux-arm-msm@...r.kernel.org,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-phy@...ts.infradead.org, linux-pm@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v7 05/10] nvmem: qcom-spmi-sdam: Migrate to
 devm_spmi_subdevice_alloc_and_add()

On 1/14/26 10:55 AM, Andy Shevchenko wrote:
> On Wed, Jan 14, 2026 at 10:47:20AM +0100, Konrad Dybcio wrote:
>> On 1/14/26 10:42 AM, Andy Shevchenko wrote:
>>> On Wed, Jan 14, 2026 at 10:09:45AM +0100, AngeloGioacchino Del Regno wrote:
>>>> Il 14/01/26 10:07, Andy Shevchenko ha scritto:
>>>>> On Wed, Jan 14, 2026 at 10:03:57AM +0100, AngeloGioacchino Del Regno wrote:
>>>>>> Il 14/01/26 10:00, Andy Shevchenko ha scritto:
>>>>>>> On Wed, Jan 14, 2026 at 09:59:40AM +0100, AngeloGioacchino Del Regno wrote:
>>>>>>>> Il 14/01/26 09:56, Andy Shevchenko ha scritto:
>>>>>>>>> On Wed, Jan 14, 2026 at 09:39:52AM +0100, AngeloGioacchino Del Regno wrote:
> 
> ...
> 
>>>>>>>>>> +	struct regmap_config sdam_regmap_config = {
>>>>>>>>>> +		.reg_bits = 16,
>>>>>>>>>> +		.val_bits = 8,
>>>>>>>>>
>>>>>>>>>> +		.max_register = 0x100,
>>>>>>>>>
>>>>>>>>> Are you sure? This might be a bad naming, but here max == the last accessible.
>>>>>>>>> I bet it has to be 0xff (but since the address is 16-bit it might be actually
>>>>>>>>> 257 registers, but sounds very weird).
>>>>>>>>
>>>>>>>> Yes, I'm sure.
>>>>>>>
>>>>>>> So, what is resided on address 0x100 ?
>>>>>>
>>>>>> I don't remember, this is research from around 5 months ago, when I've sent
>>>>>> the v1 of this.
>>>>>>
>>>>>> If you really want though, I can incorrectly set max_register to 0xff.
>>>>>
>>>>> Why incorrectly? Can you dig into the datasheet and check, please? We don't
>>>>> know what is the 0x100 address means.
>>>>
>>>> I don't have any datasheets for Qualcomm IPs.
>>>
>>> Hmm... Can we have somebody from QC to check on this?
>>> Perhaps Dmitry?
>>
>> 0xe6 is the last usable register today
> 
> Thanks for checking!
> 
>> But I wouldn't mind either 0xff or 0x100 because I don't want
>> anyone to pull their hair out if a regmap access is dropped some day..
> 
> There is actually about the exact window size where registers are belong to the
> same entity (subdevice). As in the HW world most of the things are stuck with
> power-of-two numbers, and taking into account the naming of the field, I do not
> believe one provides a 257 (256 + 1 = 2⁸ + 1) register _windows_ ("s" is also
> important here, as it points out to the pattern) for the subdevices. I bet the
> 0xff, i.e. 256, is the *correct* window from the HW perspective.

Right, [0x100n, 0x100n + 0xff] inclusive is the reserved register window
for all Qualcomm PMIC peripherals, so I guess 0xff is the correct choice
here

If a peripheral is more complex, it's split into a couple of these
same-sized blocks

Konrad