From: Guenter Roeck <linux@roeck-us.net>
To: Bjorn Helgaas <bhelgaas@google.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
Will Deacon <Will.Deacon@arm.com>
Subject: Re: [PATCH] PCI: Only enable IO window if supported
Date: Wed, 03 Jun 2015 08:15:46 -0700 [thread overview]
Message-ID: <556F1A22.7050400@roeck-us.net> (raw)
In-Reply-To: <CAErSpo4WyQqc+En6hAB9B63sszKc8B93FiycwaDG42tecSB9Mg@mail.gmail.com>
Bjorn,
On 06/02/2015 12:58 PM, Bjorn Helgaas wrote:
> On Tue, Jun 2, 2015 at 12:02 PM, Guenter Roeck <linux@roeck-us.net> wrote:
[ ... ]
>>>>
>>>> I wonder if we can do the same with pci_read_bridge_mmio_pref(), and
>>>> somehow get rid of pci_bridge_check_ranges() altogether?
>>>>
>>>> I think I looked at doing that a while back, and it seems like there was
>>>> some wrinkle, but I don't remember what it was.
>>
>> After looking into this some more, I think the wrinkle may be that
>> pci_read_bridge_bases() and thus pci_read_bridge_io() isn't called
>> on probe-only systems (if PCI_PROBE_ONLY is set). A secondary
>> problem is that pci_read_bridge_io() does not enable a resource
>> if it is explicitly disabled (base > limit), but the subsequent call
>> to pci_bridge_check_ranges() unconditionally enables it.
>
> I haven't researched this, but it sounds wrong that we skip
> pci_read_bridge_bases() if PCI_PROBE_ONLY is set. I think
> PCI_PROBE_ONLY should mean "look, but don't touch." So I think we
> should always look at the bridge windows, and my advice is to see if
> it looks reasonable to change this aspect of PCI_PROBE_ONLY.
>
Looks like Lorenzo's patch is going to take care of that problem.
How about the second problem mentioned above ? One option might be to
keep pci_bridge_check_ranges() but only use it to _enable_ the various
ranges (and maybe rename it accordingly) ?
Thanks,
Guenter
next prev parent reply other threads:[~2015-06-03 15:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-23 0:52 [PATCH] PCI: Only enable IO window if supported Guenter Roeck
2015-05-27 21:04 ` Bjorn Helgaas
2015-05-28 2:23 ` Guenter Roeck
2015-05-28 12:41 ` Bjorn Helgaas
2015-06-18 18:01 ` Guenter Roeck
2015-06-18 19:51 ` Bjorn Helgaas
2015-06-18 20:53 ` Guenter Roeck
2015-06-19 16:24 ` Lorenzo Pieralisi
2015-07-07 14:40 ` Lorenzo Pieralisi
2015-07-07 15:01 ` Guenter Roeck
2015-07-07 17:28 ` Lorenzo Pieralisi
2015-07-07 18:13 ` Guenter Roeck
2015-06-02 14:55 ` Lorenzo Pieralisi
2015-06-02 16:32 ` Bjorn Helgaas
2015-06-02 17:02 ` Guenter Roeck
2015-06-02 19:58 ` Bjorn Helgaas
2015-06-03 15:15 ` Guenter Roeck [this message]
2015-06-03 10:32 ` Lorenzo Pieralisi
2015-06-03 15:12 ` Guenter Roeck
2015-06-03 16:55 ` Lorenzo Pieralisi
2015-06-03 18:07 ` Guenter Roeck
2015-06-23 22:46 ` Benjamin Herrenschmidt
2015-06-23 23:02 ` Bjorn Helgaas
2015-06-23 23:14 ` Benjamin Herrenschmidt
2015-06-25 11:27 ` Lorenzo Pieralisi
2015-07-08 8:38 ` Lorenzo Pieralisi
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