From: Lee Jones <lee.jones@linaro.org>
To: Michael Walle <michael@walle.cc>
Cc: Frank Rowand <frowand.list@gmail.com>,
andy.shevchenko@gmail.com, robh+dt@kernel.org,
broonie@kernel.org, devicetree@vger.kernel.org,
linus.walleij@linaro.org, linux@roeck-us.net,
andriy.shevchenko@linux.intel.com, robin.murphy@arm.com,
gregkh@linuxfoundation.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes
Date: Wed, 24 Jun 2020 09:23:52 +0100 [thread overview]
Message-ID: <20200624082352.GF954398@dell> (raw)
In-Reply-To: <7a31b34940984b3f0921ed2d4fb29a58@walle.cc>
On Wed, 24 Jun 2020, Michael Walle wrote:
> Hi,
>
> Am 2020-06-24 08:41, schrieb Lee Jones:
> > On Tue, 23 Jun 2020, Frank Rowand wrote:
> >
> > > On 2020-06-11 14:10, Lee Jones wrote:
> > > > Currently, when a child platform device (sometimes referred to as a
> > > > sub-device) is registered via the Multi-Functional Device (MFD) API,
> > > > the framework attempts to match the newly registered platform device
> > > > with its associated Device Tree (OF) node. Until now, the device has
> > > > been allocated the first node found with an identical OF compatible
> > > > string. Unfortunately, if there are, say for example '3' devices
> > > > which are to be handled by the same driver and therefore have the same
> > > > compatible string, each of them will be allocated a pointer to the
> > > > *first* node.
> > >
> > > As you mentioned elsewhere in this thread, this series "fixes" the
> > > problem related to the "stericsson,ab8500-pwm" compatible.
> > >
> > > I know, I said I would drop discussion of that compatible, but bear
> > > with me for a second. :-)
> > >
> > > The "problem" is that the devices for multiple mfd child nodes with
> > > the same compatible value of "stericsson,ab8500-pwm" will all have
> > > a pointer to the first child node. At the moment the same child
> > > of_node being used by more than one device does not cause any
> > > incorrect behavior.
> > >
> > > Just in case the driver for "stericsson,ab8500-pwm" is modified
> > > in a way that the child of_node needs to be distinct for each
> > > device, and that changes gets back ported, it would be useful
> > > to have Fixes: tags for this patch series.
> > >
> > > So, at your discretion (and I'll let you worry about the correct
> > > Fixes: tag format), this series fixes:
> > >
> > > bad76991d7847b7877ae797cc79745d82ffd9120 mfd: Register ab8500
> > > devices using the newly DT:ed MFD API
> >
> > This patch isn't actually broken.
> >
> > The issue is the DTB, which [0] addresses.
> >
> > [0]
> > https://lkml.kernel.org/lkml/20200622083432.1491715-1-lee.jones@linaro.org/
>
> Now, I'm confused; because this patch doesn't use the reg property
> but a different node name.
The fix mentioned above is orthogonal to this set.
The *only* reason for the differing node names there is to circumvent
the following DTC warnings:
arch/arm/boot/dts/ste-ab8500.dtsi:210.16-214.7: ERROR (duplicate_node_names): /soc/prcmu@80157000/ab8500/ab8500-pwm: Duplicate node name
arch/arm/boot/dts/ste-ab8500.dtsi:216.16-220.7: ERROR (duplicate_node_names): /soc/prcmu@80157000/ab8500/ab8500-pwm: Duplicate node name
arch/arm/boot/dts/ste-ab8500.dtsi:216.16-220.7: ERROR (duplicate_node_names): /soc/prcmu@80157000/ab8500/ab8500-pwm: Duplicate node name
> I'd actually prefer this for any MFD
> driver which has multiple nodes of the same compatible string. See
> my reasoning here [1]. But until now, no one has responded. Thus,
> I'd rather see a OF_MFD_CELL_NAME() which matches the node name
> instead of the OF_MFD_CELL_REG() macro.
>
> This would also circumvent the fact that the unit-address has one
> number space. Eg. it is not possible to have:
>
> mfd {
> compatible = "mfd,compatible";
>
> gpio@0 {
> reg = <0>;
> };
> gpio@1 {
> reg = <1>;
> };
> pwm@0 {
> reg = <0>;
> };
> };
>
> Although Rob mentioned to maybe relax that, but I sill fail to see
> the advantage to have an arbitrary reg property instead of a unique
> node name.
I don't have a strong opinion either way.
We can *also* add node name matching if Rob deems it fit.
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog
next prev parent reply other threads:[~2020-06-24 8:24 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-11 19:10 [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes Lee Jones
2020-06-11 19:10 ` [PATCH v2 2/3] mfd: core: Fix formatting of MFD helpers Lee Jones
2020-06-12 12:27 ` Frank Rowand
2020-06-11 19:10 ` [PATCH v2 3/3] mfd: core: Add OF_MFD_CELL_REG() helper Lee Jones
2020-06-12 12:28 ` Frank Rowand
2020-06-12 12:26 ` [PATCH v2 1/3] mfd: core: Make a best effort attempt to match devices with the correct of_nodes Frank Rowand
2020-06-15 1:19 ` Frank Rowand
2020-06-15 9:26 ` Lee Jones
2020-06-18 17:34 ` Frank Rowand
2020-06-22 8:50 ` Lee Jones
2020-06-22 14:32 ` Frank Rowand
2020-06-22 14:35 ` Frank Rowand
2020-06-22 15:10 ` Lee Jones
2020-06-22 18:01 ` Frank Rowand
2020-06-22 18:04 ` Frank Rowand
2020-06-22 19:11 ` Lee Jones
2020-06-22 22:23 ` Frank Rowand
2020-06-23 1:17 ` Frank Rowand
2020-06-23 1:37 ` Frank Rowand
2020-06-23 6:47 ` Lee Jones
2020-06-23 17:55 ` Frank Rowand
2020-06-23 19:59 ` Lee Jones
2020-06-23 22:33 ` Frank Rowand
2020-06-24 7:46 ` Lee Jones
2020-06-24 15:51 ` Frank Rowand
2020-06-24 16:14 ` Lee Jones
2020-06-24 16:25 ` Frank Rowand
2020-06-22 8:09 ` Lee Jones
2020-06-22 16:09 ` Frank Rowand
2020-06-22 16:53 ` Lee Jones
2020-06-23 22:21 ` Frank Rowand
2020-06-24 6:45 ` Lee Jones
2020-06-23 23:03 ` Frank Rowand
2020-06-24 6:41 ` Lee Jones
2020-06-24 7:47 ` Michael Walle
2020-06-24 8:23 ` Lee Jones [this message]
2020-06-24 9:19 ` Michael Walle
2020-06-24 11:24 ` Lee Jones
2020-06-11 19:12 Lee Jones
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