linux-kernel - Re: driver skip pci_set

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Message-ID: <CAErSpo6KuYLaoEsxR4jJQ98P23kNEMzMcu_-RyM3nWd6YRxgag@mail.gmail.com>
Date:	Tue, 8 Apr 2014 12:27:16 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Mark Lord <mlord@...ox.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	"Theodore Ts'o" <tytso@....edu>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: driver skip pci_set_master, fix it? No.

[+cc Ben, linux-pci]

On Tue, Apr 8, 2014 at 10:34 AM, Mark Lord <mlord@...ox.com> wrote:
> I am working a couple of drivers for chips that perform extensive bus-mastering ops.
> These including full SRIOV support, and allow assigning virtual functions to virtual machines, etc.
>
> One thing the driver (still in development) does for safety,
> is defer the call to pci_set_master() until *after* it has mapped
> the MMIO space of the chips, so it can reset/flush the DMA engines
> before giving them permission to scribble over host RAM.
>
> But a recent patch to the kernel has removed this from the driver's control.
> The core PCI now does pci_set_master() immediately on pci_enable_device().

I assume you're talking about the one added by cf3e1feba7f9 ("PCI:
Workaround missing pci_set_master in pci drivers"), but as far as I
can tell, it only calls pci_set_master() for *bridge* devices.  What
am I missing?  Is pci_set_master() being called for your endpoint?
What path is that?

Bjorn
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