Linux-mediatek Archive on lore.kernel.org
 help / color / Atom feed
From: Tomasz Figa <tfiga@chromium.org>
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	linux-devicetree <devicetree@vger.kernel.org>,
	"Nicolas Boichat" <drinkcat@chromium.org>,
	srv_heupstream <srv_heupstream@mediatek.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	"Shengnan Wang (王圣男)" <shengnan.wang@mediatek.com>,
	"Louis Kuo" <louis.kuo@mediatek.com>,
	"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
	"Sj Huang" <sj.huang@mediatek.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-mediatek@lists.infradead.org>,
	"Dongchun Zhu" <dongchun.zhu@mediatek.com>,
	"Sakari Ailus" <sakari.ailus@linux.intel.com>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Cao Bing Bu" <bingbu.cao@intel.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,
	" <linux-arm-kernel@lists.infradead.org>,
	"Linux Media Mailing List" <linux-media@vger.kernel.org>
Subject: Re: [PATCH V11 2/2] media: i2c: ov02a10: Add OV02A10 image sensor driver
Date: Tue, 30 Jun 2020 16:40:12 +0200
Message-ID: <CAAFQd5CwwLzGKiCPdd_EzipmXPA2aYBrk0QRPv6Bacy++tXrHA@mail.gmail.com> (raw)
In-Reply-To: <20200630143705.GW3703480@smile.fi.intel.com>

On Tue, Jun 30, 2020 at 4:37 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Jun 30, 2020 at 04:21:31PM +0200, Tomasz Figa wrote:
> > On Tue, Jun 30, 2020 at 4:19 PM Tomasz Figa <tfiga@chromium.org> wrote:
> > > On Tue, Jun 30, 2020 at 11:54 AM Sakari Ailus
> > > <sakari.ailus@linux.intel.com> wrote:
>
> ...
>
> > > > > +     ov02a10->rst_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> > > >
> > > >
> > > > Shouldn't this be GPIOD_OUT_HIGH? That's the state it'll be after powering
> > > > the sensor off the first time. Alternatively make reset signal high in
> > > > runtime suspend callback.
> > >
> > > We might want to keep the signals low when the regulators are powered
> > > down, to reduce the leakage.
> >
> > Ah, I actually recall that the reset pin was physically active low, so
> > we would indeed better keep it at HIGH. Sorry for the noise.
>
> Here HIGH means "asserted", so in the code above it's LOW, means "deasserted",
> i.o.w. non-reset state. I dunno what is better, it depends to the firmware /
> driver expectations of the device configuration (from the power point of view,
> HIGH makes sense here, and not LOW, i.o.w. asserted reset line).
>
> And nice of the logical state that it doesn't depend to the active low / high
> (the latter just transparent to the user).

Yeah, after reading through the GPIO subsystem documentation and
discussing with a bunch of people on how to interpret it, we concluded
that the driver needs to deal only with the logical state of the
signal.

Actually, I later realized that the problem of leakage should likely
be solved by pinctrl suspend settings, based on given hardware
conditions, rather than the driver explicitly.

Best regards,
Tomasz

_______________________________________________
Linux-mediatek mailing list
Linux-mediatek@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-mediatek

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30  2:49 [PATCH V11 0/2] media: i2c: Add support for 0V02A10 sensor Dongchun Zhu
2020-06-30  2:49 ` [PATCH V11 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings Dongchun Zhu
2020-06-30 16:59   ` Tomasz Figa
2020-06-30  2:49 ` [PATCH V11 2/2] media: i2c: ov02a10: Add OV02A10 image sensor driver Dongchun Zhu
2020-06-30  9:54   ` Sakari Ailus
2020-06-30 14:19     ` Tomasz Figa
2020-06-30 14:21       ` Tomasz Figa
2020-06-30 14:37         ` Andy Shevchenko
2020-06-30 14:40           ` Tomasz Figa [this message]
2020-07-01  7:58             ` Dongchun Zhu
2020-06-30 17:07   ` Tomasz Figa
2020-06-30 18:47     ` Sakari Ailus
2020-07-01  8:47       ` Dongchun Zhu
2020-07-01  9:00         ` Sakari Ailus

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAAFQd5CwwLzGKiCPdd_EzipmXPA2aYBrk0QRPv6Bacy++tXrHA@mail.gmail.com \
    --to=tfiga@chromium.org \
    --cc=andriy.shevchenko@linux.intel.com \
    --cc=bgolaszewski@baylibre.com \
    --cc=bingbu.cao@intel.com \
    --cc=devicetree@vger.kernel.org \
    --cc=dongchun.zhu@mediatek.com \
    --cc=drinkcat@chromium.org \
    --cc=linus.walleij@linaro.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-mediatek@lists.infradead.org \
    --cc=louis.kuo@mediatek.com \
    --cc=mark.rutland@arm.com \
    --cc=matthias.bgg@gmail.com \
    --cc=mchehab@kernel.org \
    --cc=robh+dt@kernel.org \
    --cc=sakari.ailus@linux.intel.com \
    --cc=shengnan.wang@mediatek.com \
    --cc=sj.huang@mediatek.com \
    --cc=srv_heupstream@mediatek.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-mediatek Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-mediatek/0 linux-mediatek/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-mediatek linux-mediatek/ https://lore.kernel.org/linux-mediatek \
		linux-mediatek@lists.infradead.org
	public-inbox-index linux-mediatek

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-mediatek


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git