linux-kernel - Re: [PATCH v9 27/28] media: iris: enable video driver probe of SM8250 SoC

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: <067d0deb-50ea-46bd-9f09-827b0ba61aa3@xs4all.nl>
Date: Wed, 8 Jan 2025 11:43:45 +0100
From: Hans Verkuil <hverkuil@...all.nl>
To: Dikshita Agarwal <quic_dikshita@...cinc.com>,
 Nicolas Dufresne <nicolas@...fresne.ca>,
 Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
 Sebastian Fricke <sebastian.fricke@...labora.com>
Cc: Vikash Garodia <quic_vgarodia@...cinc.com>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>,
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Uwe Kleine-König <u.kleine-koenig@...libre.com>,
 Jianhua Lu <lujianhua000@...il.com>,
 Stefan Schmidt <stefan.schmidt@...aro.org>, linux-media@...r.kernel.org,
 linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 27/28] media: iris: enable video driver probe of SM8250
 SoC

On 1/8/25 11:21, Dikshita Agarwal wrote:
> 
> 
> On 1/8/2025 2:25 PM, Hans Verkuil wrote:
>> On 08/01/2025 09:51, Dikshita Agarwal wrote:
>>>
>>>
>>> On 1/8/2025 1:17 PM, Hans Verkuil wrote:
>>>> On 08/01/2025 08:43, Dikshita Agarwal wrote:
>>>>>
>>>>>
>>>>> On 1/7/2025 7:27 PM, Nicolas Dufresne wrote:
>>>>>> Le lundi 23 décembre 2024 à 16:21 +0530, Dikshita Agarwal a écrit :
>>>>>>>
>>>>>>> On 12/23/2024 4:00 PM, Mauro Carvalho Chehab wrote:
>>>>>>>> Em Thu, 12 Dec 2024 17:21:49 +0530
>>>>>>>> Dikshita Agarwal <quic_dikshita@...cinc.com> escreveu:
>>>>>>>>
>>>>>>>>> +	.dma_mask = GENMASK(31, 29) - 1,
>>>>>>>>
>>>>>>>> Setting a mask to GENMASK() - 1 sounds weird. Is it really what you want?
>>>>>>>> I so, why?
>>>>>>>>
>>>>>>> Hi Mauro,
>>>>>>>
>>>>>>> the value of this dma mask should be 0xe0000000 -1.
>>>>>>>
>>>>>>> The background for the same is, 0xe0000000 onward memory space is allocated
>>>>>>> for IO register space so we are restricting the driver buffer allocations
>>>>>>> to 0xe0000000 - 1.
>>>>>>>
>>>>>>> Based on the comments received in the past, we are using GENMASK to
>>>>>>> generate 0xe0000000.
>>>>>>>
>>>>>>> Does this answer your query or I missed something?
>>>>>>
>>>>>> I'm not sure it will do what you want. (0xe0000000 -1) matches ~BIT(29). Perhaps
>>>>>> you wanted to use ~0xe0000000. 
>>>>>>
>>>>> value of dma mask is coming as expected with GENMASK(31, 29) - 1
>>>>>
>>>>> qcom-iris aa00000.video-codec: dma_mask DFFFFFFF (0xe0000000 -1)
>>>>
>>>> Isn't this just the equivalent of GENMASK(28, 0)? Can't you use that?
>>
>> Too early in the morning, this suggestion was clearly wrong.
>>
>>>>
>>>> It's much easier to understand than GENMASK()-1.
>>>
>>> Sure, I can use either ~GENMASK(29, 29) or ~BIT(29),
>>
>> ~BIT(29).
>>
>> It's really weird to just disable a single bit, so I think some comments
>> explaining why this mask is needed would be good (if there aren't comments
>> already).
>>
> I tested this some more, and seems ~BIT(29) doesn't work, as its still
> conflicting with the register space.

Odd, perhaps a 64 vs 32 bit issue?

> Correct value would be GENMASK(31,30) + GENMASK(28,0) to set the exact bits
> to get the desired value i.e 0xe0000000 -1

Honestly, in this case I would prefer to just go with the actual hex value
0xdfffffff together with an explanatory comment.

Regards,

	Hans

>> Regards,
>>
>> 	Hans
>>
>>> Please let me know which would be better?
>>>
>>> Thanks,
>>> Dikshita
>>>
>>>>
>>>> Regards,
>>>>
>>>> 	Hans
>>>>
>>>>>
>>>>> Thanks,
>>>>> Dikshita
>>>>>> Nicolas
>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Dikshita
>>>>>>>> Thanks,
>>>>>>>> Mauro
>>>>>>
>>>>
>>>>
>>