From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Rob Herring <robh+dt@kernel.org>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Wysocki, Rafael J" <rafael.j.wysocki@intel.com>,
"Frank Rowand" <frowand.list@gmail.com>,
"Florian Fainelli" <f.fainelli@gmail.com>,
"moderated list:BROADCOM BCM2835 ARM ARCHITECTURE"
<linux-rpi-kernel@lists.infradead.org>,
"Saravana Kannan" <saravanak@google.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
devicetree@vger.kernel.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC] of/platform: Create device link between simple-mfd and its children
Date: Fri, 16 Oct 2020 17:26:56 +0200 [thread overview]
Message-ID: <0f0b7021e85a832afd42c6f9016158d6d8b0b28b.camel@suse.de> (raw)
In-Reply-To: <CAL_JsqLvzsdAfx56jQqPSd1r=P20C8DURKKZ9kke-L2owqr0fg@mail.gmail.com>
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On Fri, 2020-10-16 at 09:38 -0500, Rob Herring wrote:
> On Thu, Oct 15, 2020 at 6:43 AM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> wrote:
> > 'simple-mfd' usage implies there might be some kind of resource sharing
> > between the parent device and its children.
>
> It does? No! The reason behind simple-mfd was specifically because
> there was no parent driver or dependency on the parent. No doubt
> simple-mfd has been abused.
Fair enough, so we're doing things wrong. Just for the record, I'm looking at
RPi´s firmware interface:
firmware: firmware {
compatible = "raspberrypi,bcm2835-firmware", "simple-mfd";
#address-cells = <1>;
#size-cells = <1>;
mboxes = <&mailbox>;
firmware_clocks: clocks {
compatible = "raspberrypi,firmware-clocks";
#clock-cells = <1>;
};
reset: reset {
compatible = "raspberrypi,firmware-reset";
#reset-cells = <1>;
};
[...]
};
Note that "raspberrypi,bcm2835-firmware" has a driver, it's not just a
placeholder. Consumer drivers get a handle to RPi's firmware interface through
the supplier's API, rpi_firmware_get(). The handle to firmware becomes
meaningless if it is unbinded, which I want to protect myself against.
A simpler solution would be to manually create a device link between both
devices ("raspberrypi,bcm2835-firmware" and "raspberrypi,firmware-clocks" for
example) upon calling rpi_firmware_get(). But I wanted to try addressing the
problem in a generic way first.
Regards,
Nicolas
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next prev parent reply other threads:[~2020-10-16 15:27 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-15 11:43 [RFC] of/platform: Create device link between simple-mfd and its children Nicolas Saenz Julienne
2020-10-15 16:52 ` Saravana Kannan
2020-10-16 15:39 ` Nicolas Saenz Julienne
2020-10-16 14:38 ` Rob Herring
2020-10-16 15:26 ` Nicolas Saenz Julienne [this message]
2020-10-19 6:52 ` Uwe Kleine-König
2020-10-21 11:35 ` Nicolas Saenz Julienne
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