Date: Fri, 21 May 2004 02:04:12 -0600 (MDT) From: "M. Warner Losh" <imp@bsdimp.com> To: scottl@freebsd.org Cc: cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/pci pci.c Message-ID: <20040521.020412.118756775.imp@bsdimp.com> In-Reply-To: <40ADAF07.2070909@freebsd.org> References: <200405210636.i4L6aadV059034@repoman.freebsd.org> <40ADAF07.2070909@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
In message: <40ADAF07.2070909@freebsd.org>
Scott Long <scottl@freebsd.org> writes:
: Warner Losh wrote:
: > imp 2004/05/20 23:36:36 PDT
: >
: > FreeBSD src repository
: >
: > Modified files:
: > sys/dev/pci pci.c
: > Log:
: > MFp4: o save/restore subvendor, subdevice, vendor, device, baseclass,
: > subclass, progif and revid. While these are typically read
: > only fields, they aren't always read-only. progif is writable
: > for ata devices, for example. It does no harm when they are
: > read only, and helps when they aren't.
: >
: > Revision Changes Path
: > 1.252 +16 -0 src/sys/dev/pci/pci.c
:
: Shouldn't it be left up to the device drivers to decide if a buggy piece
: of silicon needs to be touched like this? I really don't like the bus
: unilaterally enforcing this on everything.
This just preserves the values across a D3 -> D0 state transition.
This seems to be required by the 1.1 version of the pci power spec:
Section 5.4: "When a function is brought back to D0...,
software will need to perform a full initialization of the
function, including its PCI Configuration space."
Section 8.3.3: For example, reinitialization includes, but is
not necessarily limited to, restoring the Base Address
registers, re-enabling the I/O and memory spaces, re-enabling
bus master capabilities, and unmasking any IRQs or PCI
Interrupts as well as restoring the INT Line
register. Furthermore, if the function has the DSI bit set,
the operating system is required to execute whatever
initialization code is necessary, either via the device
driver's initialization code or by executing POST.
My reading of these two sections lead me to save this information.
Warner
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20040521.020412.118756775.imp>