linux-kernel - Re: Problem sharing interrupts between gpioa and uart0 on Broadcom Hurricane 2 (iProc)

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Date:   Tue, 1 Oct 2019 03:04:36 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     "rayagonda.kokatanur@...adcom.com" <rayagonda.kokatanur@...adcom.com>,
        "bcm-kernel-feedback-list@...adcom.com" 
        <bcm-kernel-feedback-list@...adcom.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "li.jin@...adcom.com" <li.jin@...adcom.com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "sbranden@...adcom.com" <sbranden@...adcom.com>,
        "rjui@...adcom.com" <rjui@...adcom.com>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: Problem sharing interrupts between gpioa and uart0 on Broadcom
 Hurricane 2 (iProc)

Hi Florian,

On Mon, 2019-09-30 at 19:54 -0700, Florian Fainelli wrote:
> 
> On 9/30/2019 7:33 PM, Chris Packham wrote:
> > Hi,
> > 
> > We have a platform using the BCM53344 integrated switch/CPU. This is
> > part of the Hurricane 2 (technically Wolfhound) family of devices.
> > 
> > Currently we're using pieces of Broadcom's "iProc" SDK based on an out
> > of date kernel and we'd very much like to be running as close to
> > upstream as possible. The fact that the Ubiquiti UniFi Switch 8 is
> > upstream gives me some hope.
> 
> FYI, I could not get enough information from the iProc SDK to port (or
> not) the clock driver, so if nothing else, that is an area that may
> require immediate work (though sometimes fixed-clocks would do just fine).

Setting a fixed clock seems to work for me. At least for now.

> 
> > 
> > My current problem is the fact that the uart0 interrupt is shared with
> > the Chip Common A gpio block. When I have and interrupt node on the
> > gpio in the device tree I get an init exit at startup. If I remove the
> > interrupt node the system will boot (except I don't get cascaded
> > interrupts from the GPIOs).
> > 
> > Looking at the pinctrl-nsp-gpio.c it looks as though I might be able to
> > make this work if I can convince the gpio code to return IRQ_HANDLED or
> > IRQ_NONE but I'm struggling against the fact that the pinctrl-iproc-
> > gpio.c defers it's interrupt handing to the gpio core.
> 
> Not sure I follow you here, what part is being handed to gpiolib? The
> top interrupt handler under nsp_gpio_irq_handler() will try to do
> exactly as you described. In fact, there are other iProc designs where
> "gpio-a" and another interrupt, arch/arm/boot/dts/bcm-nsp.dtsi is one
> such example and I never had problems with that part of NSP.
> 

nsp_gpio_probe() creates the irq domain directly and
nsp_gpio_irq_handler() directly deals with sharing by returning
IRQ_HANDLED or IRQ_NONE depending on whether it has a bit set.

iproc_gpio_probe() on the sets iproc_gpio_irq_handler() as the
parent_handler and defers to gpiolib to deal with the irq domain etc.

I'm currently assuming this is why I can't have uart0 and gpio
interrupts. But of course I could be completely wrong.

> > 
> > Is there any way I can get the gpio core to deal with the shared
> > interrupt?