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From:   yang tylor <tylor_yang@himax.corp-partner.google.com>
Date:   Tue, 26 Sep 2023 17:52:39 +0800
Message-ID: <CAGD2q_YBfDT950tyxEF87ZeiANgea_x8S16Ud5K2bcQ+eL9T=w@mail.gmail.com>
Subject: Re: [PATCH V2 1/2] dt-bindings: input: Introduce Himax HID-over-SPI device
To:     Conor Dooley <conor@kernel.org>
Cc:     Conor Dooley <conor.dooley@microchip.com>,
        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 Tue, Sep 26, 2023 at 5:02=E2=80=AFPM Conor Dooley <conor@kernel.org> wro=
te:
>
> On Mon, Sep 25, 2023 at 06:16:29PM +0800, yang tylor wrote:
> > On Mon, Sep 25, 2023 at 4:41=E2=80=AFPM Conor Dooley <conor.dooley@micr=
ochip.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@ker=
nel.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=
@kernel.org> wrote:
> > > > > > > > > On Tue, Sep 19, 2023 at 05:31:29PM +0800, yang tylor wrot=
e:
> > > > > > >
> > > > > > > > > > The behavior of "himax,boot_time_fw_upgrade" seems not =
stable and
> > > > > > > > > > should be removed. "himax,fw_in_flash", I use the kerne=
l config for
> > > > > > > > > > user to select.
> > > > > > > > >
> > > > > > > > > That seems like a bad idea, we want to be able to build o=
ne kernel 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 i=
n flash and
> > > > > > > others where it would never be? Or is this a choice made by t=
he board 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, ne=
ed to
> > > > > > 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 IC=
s that
> > > > > will need to load the firmware from flash and there are some wher=
e it
> > > > > will be a decision made by the designer of the board. Is the flas=
h part
> > > > > of the IC or is it an external flash chip?
> > > > >
> > > >
> > > > Both are possible, it depends on the IC type. For TDDI, the IC is l=
ong
> > > > and thin, placed on panel PCB, flash will be located at the externa=
l
> > > > flash chip. For the OLED TP, IC is usually placed at FPC and its fl=
ash
> > > > is embedded, thus the IC size is large compared to TDDI. But from t=
he
> > > > driver's perspective either external flash or embedded flash, the I=
C
> > > > itself will load firmware from flash automatically when reset pin i=
s
> > > > 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 cas=
es?
> > > If the property exists, then you know you need to load firmware & wha=
t
> > > 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 driv=
er code.
>
> How do you intend generating the name of the firmware file? I assume the
> same firmware doesn't work on every IC, so you'll need to pick a
> different one depending on the compatible?
>
If considering a firmware library line-up for all the incoming panels
of this driver.
We would use PID as part of the file name. Because all the support panels w=
ould
have a unique PID associated. Which will make the firmware name like
himax_xxx_{$PID}.bin. The problem is, we need to know PID before firmware l=
oad
at no flash condition. Thus PID information is required in dts when
no-flash-flag
is specified.

> > 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.

If a more simple solution for no-flash condition is needed, as you mentione=
d,
specifying a firmware name in dts would be the best. Otherwise, a
no-flash-flag and
PID information needs to be added in dts.

Thanks,
Tylor