linux-kernel - Re: [PATCH] i.MX6 PCIe: Fix imx6_pcie_deassert_core

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Date:	Tue, 29 Mar 2016 18:13:53 +0200
From:	Roberto Fichera <kernel@...no-soft.it>
To:	Tim Harvey <tharvey@...eworks.com>, Arnd Bergmann <arnd@...db.de>
Cc:	Lucas Stach <l.stach@...gutronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Richard Zhu <Richard.Zhu@...escale.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Krzysztof Hałasa <khalasa@...p.pl>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Petr Štetiar <ynezz@...e.cz>,
	Fabio Estevam <festevam@...il.com>
Subject: Re: [PATCH] i.MX6 PCIe: Fix imx6_pcie_deassert_core_reset() polarity

On 03/29/2016 05:10 PM, Tim Harvey wrote:
> Arnd,
>
> Right, on the IMX the MSI interrupt is GIC-120 which is also the
> legacy INTD and I do see that if I happen to put a radio in a slot
> where due to swizzling its pin1 becomes INTD (GIC-120) the interrupt
> does fire and the device works. Any other slot using GIC-123 (INTA),
> GIC-122 (INTB), or GIC-121 (INTC) never fires so its very possible
> that something in the designware core is masking out the legacy irqs.
> I would also think this was something IMX specific, but I really don't
> see any codepaths in pci-imx6.c that would cause that: a driver
> requesting a legacy PCI would get a GIC interrupt which is handled by
> the IMX6 gpc interrupt controller.
>
> Any dra7xxx, exynos, spear13xx, keystone, layerscape, hisi, qcom SoC
> users of designware PCIe core out there that can verify PCI MSI and
> legacy are both working at the same time?
>
> Lucas is the expert here and I believe he has the documentation for
> the designware core that Freescale doens't provide with the IMX6
> documentation so hopefully he can provide some insight. He's the one
> that has authored all the MSI support and has been using it.
>
> I typically advise our users to 'not' enable MSI because
> architecturally you can spread 4 distinct legacy irq's across CPU's
> better than a single shared irq.

Don't know if I'm facing similar problem, however devices connected in miniPCI slot behind
a PCIe-to-PCI bridge (MSI is disabled) using INTA all is working ok, including shared IRQ.
In case of INTB will not work, and the GIC irq quite often get stuck.