From: Jeremy Linton <jeremy.linton@arm.com>
To: Rob Herring <robh@kernel.org>
Cc: linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
PCI <linux-pci@vger.kernel.org>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Bjorn Helgaas <bhelgaas@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Sudeep Holla <sudeep.holla@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] arm64: PCI: Enable SMC conduit
Date: Thu, 7 Jan 2021 13:45:45 -0600 [thread overview]
Message-ID: <5d4f85a4-248b-b62e-f976-63c6214bf588@arm.com> (raw)
In-Reply-To: <CAL_Jsq+OUX2ctFwiqcQtM=oswyz8s-iq94eHW247sabYYF5B-A@mail.gmail.com>
Hi,
On 1/7/21 11:36 AM, Rob Herring wrote:
> On Thu, Jan 7, 2021 at 9:24 AM Jeremy Linton <jeremy.linton@arm.com> wrote:
>>
>> Hi,
>>
>>
>> On 1/7/21 9:28 AM, Rob Herring wrote:
>>> On Mon, Jan 4, 2021 at 9:57 PM Jeremy Linton <jeremy.linton@arm.com> wrote:
>>>>
>>>> Given that most arm64 platform's PCI implementations needs quirks
>>>> to deal with problematic config accesses, this is a good place to
>>>> apply a firmware abstraction. The ARM PCI SMMCCC spec details a
>>>> standard SMC conduit designed to provide a simple PCI config
>>>> accessor. This specification enhances the existing ACPI/PCI
>>>> abstraction and expects power, config, etc functionality is handled
(trimming)
>>>>
>>>> +static int smccc_pcie_check_conduit(u16 seg)
>>>
>>> check what? Based on how you use this, perhaps _has_conduit() instead.
>>
>> Sure.
>>
>>>
>>>> +{
>>>> + struct arm_smccc_res res;
>>>> +
>>>> + if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE)
>>>> + return -EOPNOTSUPP;
>>>> +
>>>> + arm_smccc_smc(SMCCC_PCI_VERSION, 0, 0, 0, 0, 0, 0, 0, &res);
>>>> + if ((int)res.a0 < 0)
>>>> + return -EOPNOTSUPP;
>>>> +
>>>> + arm_smccc_smc(SMCCC_PCI_SEG_INFO, seg, 0, 0, 0, 0, 0, 0, &res);
>>>> + if ((int)res.a0 < 0)
>>>> + return -EOPNOTSUPP;
>>>
>>> Don't you need to check that read and write functions are supported?
>>
>> In theory no, the first version of the specification makes them
>> mandatory for all implementations. There isn't a partial access method,
>> so nothing works if only read or write were implemented.
>
> Then the spec should change:
>
> 2.3.3 Caller responsibilities
> The caller has the following responsibilities:
> • The caller must ensure that this function is implemented before
> issuing a call. This function is discoverable
> by calling PCI_FEATURES with pci_func_id set to 0x8400_0132.
>
>
> I guess knowing the version is ensuring, but the 2nd sentence makes it
> seem that is how one should ensure.
Ok, yes i understand, I will add the check.
>
> Related, are there any sort of tests for the interface? I generally
> don't think the kernel's job is validating firmware (a frequent topic
> for DT), but we should have something. Maybe an SMC unittest module?
> If nothing else, seems like we should have at least one PCI_FEATURES
> call to make sure it works. We don't want to add it later only to find
> that it breaks on some firmware implementations. Though we can just
> add firmware quirks. ;)
I'm not aware of any unit tests at the moment. My testing so far has
been against these patches:
https://review.trustedfirmware.org/q/topic:"Arm_PCI_Config_Space_Interface"
But given the next version does the PCI_FEATURES calls, that will
satisfy your concern, right?
next prev parent reply other threads:[~2021-01-07 19:46 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-05 4:57 [PATCH] arm64: PCI: Enable SMC conduit Jeremy Linton
2021-01-07 15:28 ` Rob Herring
2021-01-07 16:23 ` Jeremy Linton
2021-01-07 17:36 ` Rob Herring
2021-01-07 19:45 ` Jeremy Linton [this message]
2021-01-07 20:35 ` Rob Herring
2021-01-07 18:14 ` Will Deacon
2021-01-07 19:18 ` Jeremy Linton
2021-01-07 21:05 ` Jon Masters
2021-01-07 21:49 ` Rob Herring
2021-01-08 10:32 ` Lorenzo Pieralisi
2021-01-22 19:48 ` Will Deacon
2021-01-26 16:46 ` Jeremy Linton
2021-01-26 22:54 ` Will Deacon
2021-01-28 18:50 ` Jeremy Linton
2021-01-28 23:31 ` Bjorn Helgaas
[not found] ` <CACCGGCc3zULqHgUh3Q9wA5WtPBnQ4eq_v2+1qA8bOBCQZJ5YoQ@mail.gmail.com>
2021-02-25 9:30 ` Lorenzo Pieralisi
2021-02-25 22:31 ` Jeremy Linton
2021-01-26 17:08 ` Vikram Sethi
2021-01-26 22:53 ` Will Deacon
2021-03-25 13:12 ` Lorenzo Pieralisi
2021-03-25 20:45 ` Marcin Wojtas
2021-03-25 21:12 ` Jon Masters
2021-03-26 9:27 ` Marcin Wojtas
2021-06-16 17:36 ` Jason Gunthorpe
[not found] ` <CA+kK7ZijdNERQSauEvAffR7JLbfZ512na2-9cJrU0vFbNnDGwQ@mail.gmail.com>
2021-06-18 14:05 ` Jason Gunthorpe
2021-06-19 16:34 ` Jon Masters
2021-06-19 16:38 ` Jon Masters
2021-06-20 0:26 ` Jason Gunthorpe
2021-06-18 15:10 ` Jeremy Linton
2021-01-12 16:16 ` Vidya Sagar
2021-01-12 16:57 ` Jeremy Linton
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