linux-kernel - Re: [RFC Patch 14/19] ACPI: Translate resource into master side address for bridge window resources

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Message-ID: <1713566.DBAG4gnLzK@vostro.rjw.lan>
Date:	Wed, 21 Jan 2015 15:48:09 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>,
	Tony Luck <tony.luck@...el.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [RFC Patch 14/19] ACPI: Translate resource into master side address for bridge window resources

On Wednesday, January 21, 2015 01:36:21 PM Jiang Liu wrote:
> On 2015/1/21 8:50, Rafael J. Wysocki wrote:
> > On Thursday, January 08, 2015 10:33:01 AM Jiang Liu wrote:
> >> Add translation_offset into the result address for bridge window
> >> resources to form the master side address.
> >>
> >> Currently acpi_dev_resource_{ext_}address_space() are only used for
> >> devices instead of bridges, so it won't break current users. Later
> >> it will be used to support PCI host bridge drivers.
> >>
> >> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
> >> ---
> >>  drivers/acpi/resource.c |   14 ++++++++++++++
> >>  1 file changed, 14 insertions(+)
> >>
> >> diff --git a/drivers/acpi/resource.c b/drivers/acpi/resource.c
> >> index d3aa56674bd4..16d334a1ee25 100644
> >> --- a/drivers/acpi/resource.c
> >> +++ b/drivers/acpi/resource.c
> >> @@ -203,6 +203,20 @@ static bool acpi_decode_space(struct resource *res, resource_size_t *offset,
> >>  	res->start = addr->minimum;
> >>  	res->end = addr->maximum;
> >>  
> >> +	/*
> >> +	 * For bridges that translate addresses across the bridge,
> >> +	 * translation_offset is the offset that must be added to the
> >> +	 * address on the secondary side to obtain the address on the
> >> +	 * primary side. Non-bridge devices must list 0 for all Address
> >> +	 * Translation offset bits.
> >> +	 */
> >> +	if (base->producer_consumer == ACPI_PRODUCER) {
> > 
> > OK, so the assumption is that this check is never true in the current code, right?
> Yes.
> > 
> >> +		res->start += addr->translation_offset;
> >> +		res->end += addr->translation_offset;
> >> +	} else if (addr->translation_offset) {
> > 
> > And won't this break anything even if so?
> I'm trying to follow the spec, how about giving a warning here
> instead of failure?

Yes, that would be safer IMO.


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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