linux-kernel - Re: [PATCH v1 4/5] fpga: dfl: add generic support for MSIX interrupts

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Date:   Thu, 8 Sep 2022 13:21:57 -0700 (PDT)
From:   matthew.gerlach@...ux.intel.com
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Wu Hao <hao.wu@...el.com>, Xu Yilun <yilun.xu@...el.com>,
        russell.h.weight@...el.com, basheer.ahmed.muddebihal@...el.com,
        Tom Rix <trix@...hat.com>, Moritz Fischer <mdf@...nel.org>,
        linux-fpga@...r.kernel.org,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        tianfei.zhang@...el.com, Jonathan Corbet <corbet@....net>,
        Greg KH <gregkh@...uxfoundation.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        Johan Hovold <johan@...nel.org>, Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v1 4/5] fpga: dfl: add generic support for MSIX
 interrupts



On Thu, 8 Sep 2022, Geert Uytterhoeven wrote:

> Hi Matthew,
>
> On Thu, Sep 8, 2022 at 7:34 PM <matthew.gerlach@...ux.intel.com> wrote:
>> On Thu, 8 Sep 2022, Andy Shevchenko wrote:
>>> On Wed, Sep 07, 2022 at 02:37:32PM -0700, matthew.gerlach@...ux.intel.com wrote:
>>>> On Tue, 6 Sep 2022, Andy Shevchenko wrote:
>>>>> On Tue, Sep 06, 2022 at 12:04:25PM -0700, matthew.gerlach@...ux.intel.com wrote:
>>>
>>> ...
>>>
>>>>>> +  if (fid != FEATURE_ID_AFU && fid != PORT_FEATURE_ID_ERROR &&
>>>>>> +      fid != PORT_FEATURE_ID_UINT && fid != FME_FEATURE_ID_GLOBAL_ERR) {
>>>>>> +          v = readq(base);
>>>>>> +          v = FIELD_GET(DFH_VERSION, v);
>>>>>> +
>>>>>> +          if (v == 1) {
>>>>>> +                  v =  readq(base + DFHv1_CSR_SIZE_GRP);
>>>>>
>>>>> I am already lost what v keeps...
>>>>>
>>>>> Perhaps
>>>>>
>>>>>             v = readq(base);
>>>>>             switch (FIELD_GET(DFH_VERSION, v)) {
>>>>>             case 1:
>>>>>                     ...
>>>>>                     break;
>>>>>             }
>>>>
>>>> How about?
>>>>              if (FIELD_GET(DFH_VERSION, readq(base)) == 1) {
>>>>                      ...
>>>>              }
>>>
>>> This one tends to be expanded in the future, so I would keep it switch case.
>>>
>>
>> I'm okay with using the switch statement, but how about the following?
>>
>>                 switch (FIELD_GET(DFH_VERSION, readq(base))) {
>>                  case 1:
>>                         ...
>>                         break;
>>                 }
>
> Would it make sense to print an error if a newer version than 1 is detected?
> BTW, what is the expected value when DFHv1 is not detected? Zero
> or an arbitrary number?
>
> Gr{oetje,eeting}s,
>
>                        Geert
>

Hi Geert,

Currently, DFHs that are not version 1 should be version 0. I will fill in 
the switch statement to do nothing for version 0, and the default case 
will print a warning of an unexpected version.

Thanks for the feedback.

Matthew Gerlach
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
>
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                -- Linus Torvalds
>