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From: Bjorn Helgaas <helgaas@kernel.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Sinan Kaya <okaya@kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	"Zilberman, Zeev" <zeev@amazon.com>,
	"Saidi, Ali" <alisaidi@amazon.com>
Subject: Re: [PATCH/RESEND] arm64: acpi/pci: invoke _DSM whether to preserve firmware PCI setup
Date: Wed, 12 Jun 2019 08:27:30 -0500	[thread overview]
Message-ID: <20190612132730.GB13533@google.com> (raw)
In-Reply-To: <97fd2516fdde7f9f01688af426c103806f68dd2c.camel@kernel.crashing.org>

On Wed, Jun 12, 2019 at 10:06:06AM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2019-06-11 at 18:39 -0500, Bjorn Helgaas wrote:

> > This is fine, but can we make a tiny step toward doing this in generic
> > code instead of adding more arch-specific stuff?
> > 
> > E.g., evaluate the _DSM in the generic acpi_pci_root_add(), set a
> > "preserve_config" bit in the struct acpi_pci_root, and test the bit
> > here?
> 
> I'd rather have the flag in the host bridge no ?

Oh, of course, that would make more sense.

> Talking of which, look at the ongoing discussion I have with Lorenzo
> when it comes to pci_bus_claim_resources vs. what x86 does, I'd love
> for you to chime in. I'd like to try to consolidate things further
> accross architectures but there might be reasons I don't see as to why
> things are different in that area, so ...

I don't know any reasons why things are different per arch.  In most
cases I suspect FUD.

Speaking of which, *this* patch looks like FUD because it essentially
says "Linux shouldn't change the PCI configuration on this system" but
it offers no explanation of *why* the config needs to be preserved.  I
would really like some note like "run-time firmware depends on the
addresses of device X".

Bjorn

WARNING: multiple messages have this Message-ID (diff)
From: Bjorn Helgaas <helgaas@kernel.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-pci@vger.kernel.org, Sinan Kaya <okaya@kernel.org>,
	"Zilberman, Zeev" <zeev@amazon.com>,
	"Saidi, Ali" <alisaidi@amazon.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH/RESEND] arm64: acpi/pci: invoke _DSM whether to preserve firmware PCI setup
Date: Wed, 12 Jun 2019 08:27:30 -0500	[thread overview]
Message-ID: <20190612132730.GB13533@google.com> (raw)
In-Reply-To: <97fd2516fdde7f9f01688af426c103806f68dd2c.camel@kernel.crashing.org>

On Wed, Jun 12, 2019 at 10:06:06AM +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2019-06-11 at 18:39 -0500, Bjorn Helgaas wrote:

> > This is fine, but can we make a tiny step toward doing this in generic
> > code instead of adding more arch-specific stuff?
> > 
> > E.g., evaluate the _DSM in the generic acpi_pci_root_add(), set a
> > "preserve_config" bit in the struct acpi_pci_root, and test the bit
> > here?
> 
> I'd rather have the flag in the host bridge no ?

Oh, of course, that would make more sense.

> Talking of which, look at the ongoing discussion I have with Lorenzo
> when it comes to pci_bus_claim_resources vs. what x86 does, I'd love
> for you to chime in. I'd like to try to consolidate things further
> accross architectures but there might be reasons I don't see as to why
> things are different in that area, so ...

I don't know any reasons why things are different per arch.  In most
cases I suspect FUD.

Speaking of which, *this* patch looks like FUD because it essentially
says "Linux shouldn't change the PCI configuration on this system" but
it offers no explanation of *why* the config needs to be preserved.  I
would really like some note like "run-time firmware depends on the
addresses of device X".

Bjorn

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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2019-06-12 13:27 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-03 23:41 [RFC] ARM64 PCI resource survey issue(s) Benjamin Herrenschmidt
2019-06-03 23:41 ` Benjamin Herrenschmidt
2019-06-04  1:49 ` Bjorn Helgaas
2019-06-04  1:49   ` Bjorn Helgaas
2019-06-04  3:32   ` Benjamin Herrenschmidt
2019-06-04  3:32     ` Benjamin Herrenschmidt
2019-06-04  3:37     ` Benjamin Herrenschmidt
2019-06-04  3:37       ` Benjamin Herrenschmidt
2019-06-04  6:56     ` Benjamin Herrenschmidt
2019-06-04  6:56       ` Benjamin Herrenschmidt
2019-06-04 12:49     ` Bjorn Helgaas
2019-06-04 12:49       ` Bjorn Helgaas
2019-06-04 20:41       ` Benjamin Herrenschmidt
2019-06-04 20:41         ` Benjamin Herrenschmidt
2019-06-06  9:00         ` [PATCH/RESEND] arm64: acpi/pci: invoke _DSM whether to preserve firmware PCI setup Benjamin Herrenschmidt
2019-06-06  9:00           ` Benjamin Herrenschmidt
2019-06-06  9:13           ` Ard Biesheuvel
2019-06-06  9:13             ` Ard Biesheuvel
2019-06-06 10:55             ` Benjamin Herrenschmidt
2019-06-06 10:55               ` Benjamin Herrenschmidt
2019-06-11 14:31               ` Lorenzo Pieralisi
2019-06-11 14:31                 ` Lorenzo Pieralisi
2019-06-11 22:09                 ` Benjamin Herrenschmidt
2019-06-11 22:09                   ` Benjamin Herrenschmidt
2019-06-11 22:34                   ` Ard Biesheuvel
2019-06-11 22:34                     ` Ard Biesheuvel
2019-06-11 22:40                     ` Benjamin Herrenschmidt
2019-06-11 22:40                       ` Benjamin Herrenschmidt
2019-06-12 10:21                   ` Lorenzo Pieralisi
2019-06-12 10:21                     ` Lorenzo Pieralisi
2019-06-12 22:05                     ` Benjamin Herrenschmidt
2019-06-12 22:05                       ` Benjamin Herrenschmidt
2019-06-11 14:58           ` Lorenzo Pieralisi
2019-06-11 14:58             ` Lorenzo Pieralisi
2019-06-11 22:19             ` Benjamin Herrenschmidt
2019-06-11 22:19               ` Benjamin Herrenschmidt
2019-06-12 10:08               ` Lorenzo Pieralisi
2019-06-12 10:08                 ` Lorenzo Pieralisi
2019-06-12 10:58                 ` Benjamin Herrenschmidt
2019-06-12 10:58                   ` Benjamin Herrenschmidt
2019-06-11 23:39           ` Bjorn Helgaas
2019-06-11 23:39             ` Bjorn Helgaas
2019-06-12  0:06             ` Benjamin Herrenschmidt
2019-06-12  0:06               ` Benjamin Herrenschmidt
2019-06-12 13:27               ` Bjorn Helgaas [this message]
2019-06-12 13:27                 ` Bjorn Helgaas
2019-06-12 21:46                 ` Benjamin Herrenschmidt
2019-06-12 21:46                   ` Benjamin Herrenschmidt
2019-06-12 23:58                 ` Benjamin Herrenschmidt
2019-06-12 23:58                   ` Benjamin Herrenschmidt
2019-06-10 10:11         ` [RFC] ARM64 PCI resource survey issue(s) Lorenzo Pieralisi
2019-06-10 10:11           ` Lorenzo Pieralisi
2019-06-11  5:46           ` Benjamin Herrenschmidt
2019-06-11  5:46             ` Benjamin Herrenschmidt

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