linux-kernel - Re: [PATCH v5 2/6] reset: imx8mp-audiomix: Replace mask with bit index

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Message-ID: <9ce8bcf1-7a62-44ce-81e3-f1c51f8be9b0@gmail.com>
Date: Wed, 26 Nov 2025 01:34:10 +0200
From: Laurentiu Mihalcea <laurentiumihalcea111@...il.com>
To: Philipp Zabel <p.zabel@...gutronix.de>, Frank Li <Frank.li@....com>
Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
 Fabio Estevam <festevam@...il.com>, Daniel Baluta <daniel.baluta@....com>,
 Shengjiu Wang <shengjiu.wang@....com>, devicetree@...r.kernel.org,
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, Pengutronix Kernel Team <kernel@...gutronix.de>
Subject: Re: [PATCH v5 2/6] reset: imx8mp-audiomix: Replace mask with bit
 index


On 11/25/2025 12:40 PM, Philipp Zabel wrote:
> On Di, 2025-11-25 at 01:59 -0800, Laurentiu Mihalcea wrote:
>> On 11/24/2025 7:41 AM, Frank Li wrote:
>>> On Mon, Nov 24, 2025 at 01:28:32AM -0800, Laurentiu Mihalcea wrote:
>>>> On 11/21/2025 7:38 AM, Frank Li wrote:
>>>>> On Fri, Nov 14, 2025 at 05:37:34AM -0800, Laurentiu Mihalcea wrote:
>>>>>> From: Laurentiu Mihalcea <laurentiu.mihalcea@....com>
>>>>>>
>>>>>> Replace the reset map mask with the bit index to make it clear that all
>>>>>> reset lines are managed by exactly 1 bit.
>>>>> I don't think there are benefit because I met some periphal need a magic
>>>>> number to reset.
> Toggling multiple bits in unison is different from having to write a
> magic number to a register field. The driver currently supports
> neither. That is why I suggested to change from mask to bit.
>
>>>> Please provide more information. What SoC? Which peripherals? What block control?
>>>>
>>> I can't reminder exact one. I grep some code
>>>
>>> [IMX8MP_MEDIABLK_PD_LCDIF_1] = {
>>>                 .name = "mediablk-lcdif-1",
>>>                 .clk_names = (const char *[]){ "disp1", "apb", "axi", },
>>>                 .num_clks = 3,
>>>                 .gpc_name = "lcdif1",
>>>                 .rst_mask = BIT(4) | BIT(5) | BIT(23),
>>>                 .clk_mask = BIT(4) | BIT(5) | BIT(23),
> According to the reference manual, these are three separate software
> resets for three separate clocks: lcdif_pixel_clk, lcdif_apb_clk, and
> lcdif_axi_clk.
>
>>>                 .path_names = (const char *[]){"lcdif-rd", "lcdif-wr"},
>>>                 .num_paths = 2,
>>>         },
>>>
>>> mask is more extenable and easily support more hardware in future.
> If such hardware appears in the future, it will be easy to adapt the
> driver. Usually we don't prematurely add complexity for possible future
> hardware.
>
>>> Change to bit number have not big benefit.
> It improves readability as it makes immediately clear from the code
> that all resets correspond to a single bit.
>
>> sure, I'm fine with the mask-based approach. The big idea here is to make this driver
>> usable in as many scenarios as possible.
>>
>> Philipp, please let me know if you're okay with the proposal. Will also have to tweak
>> one of the subsequent patches since, so far, we've been operating under the assumption
>> that reset lines are 1 bit.
> Given that the current code is already using mask, and if you think it
> is likely that there will be need for reset controls that require
> toggling multiple bits with a single write, I'm fine with keeping the
> mask.


ACK. Unfortunately, I don't have an use-case for this driver in which we'd want to

manage multiple underlying reset lines as a single one like in Frank's example. I'm

also assuming Frank doesn't have one either based on his previous comment.


Despite this, however, the previous version of the driver was already able to handle

this use-case. The single-bit reset restriction was introduced by this series. Therefore, I

suggest we reduce the number of changes and revert to the old behavior.


This way, we'll avoid reverting the patches if someone does ever come up with

such an use-case. I'd say the driver is simple enough that the code readability will

not be severely impacted.


Either way, I think we'd be fine with any of the two approaches in the end.


>
> regards
> Philipp