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From:   yang tylor <tylor_yang@himax.corp-partner.google.com>
Date:   Mon, 25 Sep 2023 18:16:29 +0800
Message-ID: <CAGD2q_a1nLtFj7H42f+u+J5Bih59MGS0aJLHCFJy5gM2ydys4w@mail.gmail.com>
Subject: Re: [PATCH V2 1/2] dt-bindings: input: Introduce Himax HID-over-SPI device
To:     Conor Dooley <conor.dooley@microchip.com>
Cc:     Conor Dooley <conor@kernel.org>, dmitry.torokhov@gmail.com,
        robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org,
        conor+dt@kernel.org, jikos@kernel.org,
        benjamin.tissoires@redhat.com, linux-input@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        poyuan_chang@himax.corp-partner.google.com, hbarnor@chromium.org,
        "jingyliang@chromium.org" <jingyliang@chromium.org>,
        wuxy23@lenovo.com, luolm1@lenovo.com,
        hung poyu <poyu_hung@himax.corp-partner.google.com>
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On Mon, Sep 25, 2023 at 4:41=E2=80=AFPM Conor Dooley <conor.dooley@microchi=
p.com> wrote:
>
> On Mon, Sep 25, 2023 at 09:44:21AM +0800, yang tylor wrote:
> > On Fri, Sep 22, 2023 at 11:31=E2=80=AFPM Conor Dooley <conor@kernel.org=
> wrote:
> > >
> > > On Fri, Sep 22, 2023 at 05:43:54PM +0800, yang tylor wrote:
> > > > On Fri, Sep 22, 2023 at 5:22=E2=80=AFPM Conor Dooley <conor@kernel.=
org> wrote:
> > > > >
> > > > > On Fri, Sep 22, 2023 at 03:56:25PM +0800, yang tylor wrote:
> > > > > > On Tue, Sep 19, 2023 at 7:09=E2=80=AFPM Conor Dooley <conor@ker=
nel.org> wrote:
> > > > > > > On Tue, Sep 19, 2023 at 05:31:29PM +0800, yang tylor wrote:
> > > > >
> > > > > > > > The behavior of "himax,boot_time_fw_upgrade" seems not stab=
le and
> > > > > > > > should be removed. "himax,fw_in_flash", I use the kernel co=
nfig for
> > > > > > > > user to select.
> > > > > > >
> > > > > > > That seems like a bad idea, we want to be able to build one k=
ernel that
> > > > > > > works for all hardware at the same time.
> > > > > > >
> > > > > > I see, so I should take that back?
> > > > > > I'll explain more about it.
> > > > >
> > > > > Are there particular ICs where the firmware would always be in fl=
ash and
> > > > > others where it would never be? Or is this a choice made by the b=
oard or
> > > > > system designer?
> > > > >
> > > > Most cases it's about the system designer's decision. But some ICs =
may be forced
> > > > to use flash because of its architecture(multiple IC inside, need t=
o
> > > > load firmware to
> > > > multiple IC's sram by master IC). But if there is no limitation on
> > > > this part, most system
> > > > designers will prefer flashless.
> > >
> > > Forgive me if I am not understanding correctly, there are some ICs th=
at
> > > will need to load the firmware from flash and there are some where it
> > > will be a decision made by the designer of the board. Is the flash pa=
rt
> > > of the IC or is it an external flash chip?
> > >
> >
> > Both are possible, it depends on the IC type. For TDDI, the IC is long
> > and thin, placed on panel PCB, flash will be located at the external
> > flash chip. For the OLED TP, IC is usually placed at FPC and its flash
> > is embedded, thus the IC size is large compared to TDDI. But from the
> > driver's perspective either external flash or embedded flash, the IC
> > itself will load firmware from flash automatically when reset pin is
> > released. Only if firmware is loading from the host storage system,
> > the driver needs to operate the IC in detail.
>
>
> Since there are ICs that can use the external flash or have it loaded
> from the host, it sounds like you do need a property to differentiate
> between those cases.
Yep.

> Is it sufficient to just set the firmware-name property for these cases?
> If the property exists, then you know you need to load firmware & what
> its name is. If it doesn't, then the firmware either isn't needed or
> will be automatically loaded from the external flash.
We have a default prefix firmware name(like himax_xxxx.bin) in the driver c=
ode.
So we'll look for it when no-flash-flag is specified. In our experience,
forcing a prefix firmware name helps the user to aware what firmware
they are dealing with.

Thanks,
Tylor