linux-kernel - Re: [PATCH 01/28] mfd: Add Microchip ZL3073x support

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Message-ID: <79617a32-ddc3-42c4-bdb5-c21bf985c92c@redhat.com>
Date: Mon, 14 Apr 2025 16:08:15 +0200
From: Ivan Vecera <ivecera@...hat.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Andy Shevchenko <andy@...nel.org>, netdev@...r.kernel.org,
 Michal Schmidt <mschmidt@...hat.com>,
 Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Prathosh Satish <Prathosh.Satish@...rochip.com>,
 Lee Jones <lee@...nel.org>, Kees Cook <kees@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 01/28] mfd: Add Microchip ZL3073x support



On 14. 04. 25 3:55 odp., Andy Shevchenko wrote:
> On Mon, Apr 14, 2025 at 2:52 PM Ivan Vecera <ivecera@...hat.com> wrote:
>> On 14. 04. 25 1:39 odp., Ivan Vecera wrote:
>>> On 14. 04. 25 8:36 dop., Andy Shevchenko wrote:
>>>>> What is wrong here?
>>>>>
>>>>> I have a device that uses 7-bit addresses and have 16 register pages.
>>>>> Each pages is from 0x00-0x7f and register 0x7f is used as page selector
>>>>> where bits 0-3 select the page.
>>>> The problem is that you overlap virtual page over the real one (the
>>>> main one).
>>>>
>>>> The drivers you mentioned in v2 discussions most likely are also buggy.
>>>> As I implied in the above question the developers hardly get the
>>>> regmap ranges
>>>> right. It took me quite a while to see the issue, so it's not
>>>> particularly your
>>>> fault.
>>> Hi Andy,
>>>
>>> thank you I see the point.
>>>
>>> Do you mean that the selector register should not be part of the range?
>>>
>>> If so, does it mean that I have to specify a range for each page? Like
>>> this:
>>>
>>>       {
>>>           /* Page 0 */
>>>           .range_min    = 0x000,
>>>           .range_max    = 0x07e,
>>>           .selector_reg    = ZL3073x_PAGE_SEL,
>>>           .selector_mask    = GENMASK(3, 0),
>>>           .selector_shift    = 0,
>>>           .window_start    = 0,
>>>           .window_len    = 0x7e,
>>>       },
>>>       {
>>>           /* Page 1 */
>>>           .range_min    = 0x080,
>>>           .range_max    = 0x0fe,
>>>           .selector_reg    = ZL3073x_PAGE_SEL,
>>>           .selector_mask    = GENMASK(3, 0),
>>>           .selector_shift    = 0,
>>>           .window_start    = 0,
>>>           .window_len    = 0x7e,
>>>       },
> 
> ...
> 
>> Sorry,
>> .window_len = 0x7f /* Exclude selector reg */
> 
> It actually will make things worse. If selector register is accessible
> to all of the pages, it's better to include it in all pages.

Yes :-) I know this is non-sense.
See my recent reply.

Thanks,
Ivan