Re: [PATCH] gpio: thunderx: fix irq_request_resources

From: Robert Richter <rrichter@marvell.com>
To: Tim Harvey <tharvey@gateworks.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Lokesh Vutla <lokeshvutla@ti.com>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] gpio: thunderx: fix irq_request_resources
Date: Fri, 13 Mar 2020 21:24:44 +0100	[thread overview]
Message-ID: <20200313202444.vdfdowbudlsxmqsf@rric.localdomain> (raw)
In-Reply-To: <CAJ+vNU0q7wW8JPC8FjEkD4a-ZJc1QAmVNne0w1T4MX9pd4bCyg@mail.gmail.com>

On 13.03.20 12:41:19, Tim Harvey wrote:
> On Fri, Mar 13, 2020 at 12:12 PM Robert Richter <rrichter@marvell.com> wrote:
> >
> > On 13.03.20 16:31:51, Robert Richter wrote:
> > > On 11.03.20 08:43:53, Tim Harvey wrote:
> > > > If there are no parent resources do not call irq_chip_request_resources_parent
> > > > at all as this will return an error.
> > > >
> > > > This resolves a regression where devices using a thunderx gpio as an interrupt
> > > > would fail probing.
> > > >
> > > > Fixes: 0d04d0c ("gpio: thunderx: Use the default parent apis for {request,release}_resources")
> > > > Signed-off-by: Tim Harvey <tharvey@gateworks.com>
> > > > ---
> > > >  drivers/gpio/gpio-thunderx.c | 9 ++++++---
> > > >  1 file changed, 6 insertions(+), 3 deletions(-)

> > Looking at the original code, the parent resources are requested only
> > if existing. So the change is ok.
> >
> > On the other hand, the overall change using irq_chip_{request,
> > release}_resources_parent() became pointless now. It is unreadable and
> > more complex now. Thus, commit 0d04d0c should just be reverted.
> >
> > The function interface is limited. Instead of letting the child device
> > deal with the parent, parent requests should be handled directly in
> > irq_request_resources(). Another aspect is that the code for this
> > driver has been already removed upstream and ti_sci_inta_msi.c is the
> > last remaining user of it. This speaks also for a removal by a revert.

> A revert does make the most sense to me and it works for 5.2, 5.3, and
> 5.5 but the revert fails for 5.4 and needs some manual intervention.

v5.4 should additionally revert a7fc89f9d5fc ("gpio: thunderx: Switch
to GPIOLIB_IRQCHIP"). v5.5 contains this revert too (a564ac35d605
Revert "gpio: thunderx: Switch to GPIOLIB_IRQCHIP") and the code in
that area is the same then for all kernels from 5.2 to 5.5, which is
basically a revert back to 5.1. I think this is ok.

Do you have a particular test case to test the driver that I can use
for my own testing?

Thanks,

-Robert