Date: Sat, 22 May 2004 10:38:02 -0700 (PDT) From: Nate Lawson <nate@root.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: cvs-all@freebsd.org Subject: Re: cvs commit: src/sys/dev/pci pci.c Message-ID: <20040522103658.P58631@root.org> In-Reply-To: <20040521.020412.118756775.imp@bsdimp.com> References: <200405210636.i4L6aadV059034@repoman.freebsd.org> <40ADAF07.2070909@freebsd.org> <20040521.020412.118756775.imp@bsdimp.com>
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On Fri, 21 May 2004, M. Warner Losh wrote: > 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. I didn't know the code didn't do this fully before. Yes, it is important to save/restore all the headers across a D3 transition. I don't know of any devices this breaks. -Nate
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