linux-kernel - Re: [PATCH RESEND v3 3/6] i3c: mipi-i3c-hci: Add a quirk to set PIO mode

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Message-ID: <9b8f3c29-3404-4db4-80cf-8fd1b5d018c8@amd.com>
Date: Mon, 19 Aug 2024 12:11:46 +0530
From: Shyam Sundar S K <Shyam-sundar.S-k@....com>
To: Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Guruvendra Punugupati <Guruvendra.Punugupati@....com>,
 Krishnamoorthi M <krishnamoorthi.m@....com>, linux-i3c@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND v3 3/6] i3c: mipi-i3c-hci: Add a quirk to set PIO
 mode



On 8/12/2024 15:02, Shyam Sundar S K wrote:
> Hi,
> 
> On 8/12/2024 14:47, Jarkko Nikula wrote:
>> Hi
>>
>> On 8/9/24 6:44 PM, Shyam Sundar S K wrote:
>>>> I was thinking these quirks can be passed as driver_data more cleanly
>>>> and be specific only to affected HW if AMD HW would have an unique
>>>> ACPI ID for each HW version.
>>>>
>>>> Above X86_VENDOR_AMD might be too generic if and when quirks are fixed
>>>> in the future HW :-)
>>>>
>>>> So something like:
>>>>
>>>> static const struct acpi_device_id i3c_hci_acpi_match[] = {
>>>>      {"AMDI1234", HCI_QUIRK_PIO_MODE | HCI_QUIRK_OD_PP_TIMING |
>>>> HCI_QUIRK_RESP_BUF_THLD},
>>>>      {}
>>>> };
>>>>
>>>> and set them in the i3c_hci_probe() as:
>>>>
>>>> hci->quirks = (unsigned long)device_get_match_data(&pdev->dev);
>>>
>>> Nice idea. But only problem is that MSFT wants to have the same ACPI
>>> ID present in the specification.
>>>
>>> I have replied to Andy on patch 1/6. Can you please put your remarks
>>> there?
>>>
>> Well this is implementation detail later in the series and I found it
>> better to focus ACPI ID discussion in 1/6.
>>
>>> Yeah, agreed that having X86_VENDOR_AMD is too generic, but felt its
>>> good to have additional checks only after the HW is fixed, rather than
>>> being speculative now.. :-)
>>>
>>> What would you advise?
>>> Most probably there will be future HW with either exactly same set of 
>> quirks, reduced quirks or new quirks and X86_VENDOR_AMD test will work
>> only with the first case :-)
> 
> I can add an additional check with the CPU ID and distinguish them(so
> the quirk gets applied to the affected HW versions) and just not
> restrict to X86_VENDOR_AMD, would that be fine with you?
> 
> OTOH, Since these are quirks (where its a broken hardware problems)
> and the idea you suggested is related to driver data (where driver
> data is meant to store private information about the device)
> 
> static const struct acpi_device_id i3c_hci_acpi_match[] = {
>      {"AMDI1234", HCI_QUIRK_PIO_MODE | HCI_QUIRK_OD_PP_TIMING |
> HCI_QUIRK_RESP_BUF_THLD},
>      {}
> };
> 
> does that not conflict? quirk vs driver data?
> 
> I am OK to implement it the way you prefer :-)

Jarkko, any feedback on this?

Thanks,
Shyam

> 
> Thanks,
> Shyam
> 
> 
>