Date: Wed, 20 Apr 2016 00:49:23 +0000 From: Howard Su <howard0su@gmail.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: Mis-use of BUS_PASS_ORDER_MIDDLE Message-ID: <CAAvnz_qGk%2BqAhVFKQEkt=OOErVz2bn1%2Bdc--=busy1gYc3qwCw@mail.gmail.com> In-Reply-To: <2291840.VrgKOUFVXv@ralph.baldwin.cx> References: <CAAvnz_rmbgM9t47eqV91ASXHddJjMyEucpF4_f-3Ed5pNoM8Bw@mail.gmail.com> <1611132.EbTME86UTe@ralph.baldwin.cx> <CAAvnz_oDM83miGcX_Qh0Rc2f8o=s_hkSiuPkwEacngpxhZS=Ew@mail.gmail.com> <2291840.VrgKOUFVXv@ralph.baldwin.cx>
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Can we only load the bus driver that is required by timer or pic? Then you don't need worry about acpi_pci or pcib. John Baldwin <jhb@freebsd.org>=E4=BA=8E2016=E5=B9=B44=E6=9C=8820=E6=97=A5= =E5=91=A8=E4=B8=89 =E4=B8=8A=E5=8D=883:26=E5=86=99=E9=81=93=EF=BC=9A > On Tuesday, April 19, 2016 03:42:40 PM Howard Su wrote: > > On Tue, Apr 19, 2016 at 2:53 AM John Baldwin <jhb@freebsd.org> wrote: > > > > > On Monday, April 18, 2016 11:10:12 PM Howard Su wrote: > > > > I noticed several places there are code like this, especially in > some arm > > > > low level drivers. > > > > EARLY_DRIVER_MODULE(aw_ccu, simplebus, aw_ccu_driver, > aw_ccu_devclass, > > > > 0, 0, BUS_PASS_BUS + BUS_PASS_ORDER_MIDDLE); > > > > > > > > =E2=80=8BI feel the usage of BUS_PASS_ORDER_MIDDLE is misused. Ther= e are > another > > > > macro EARLY_DRIVER_MODULE_ORDERED, which take an additional paramet= er > > > > "order". I believe BUS_PASS_ORDER_xxx is used for that parameter. > > > > > > No, this is actually correct. The _ORDERED variants actually accept = a > > > SI_ORDER_* value to determine how drivers contained in a single .ko > file > > > are registered (in particular if you have several drivers in a .ko fi= le > > > you typically want the "top-most" driver to attach last so that all t= he > > > other drivers are ready once the actual device is attached). > > > > > Why not use _ORDERED here to achieve same thing? _ORDERED(...., > > SI_ORDER_LAST, BUS_PASS_BUS)? > > > > I am thinking to add some macro like BUS_DRIVER_MODULE, > INT_DRIVER_MODULE, > > TIMER_DRIVER_MODULE, so that the driver can declare itself in such way. > If > > we can avoid usage of BUS_PASS_ORDER_XXX, the macro is much cleaner. > > > > I am plan to do is: in autoconf phase, first load timer, int and some > bus, > > etc low level drivers first, then set cold=3D0, then load other driver = to > > work around the problem that driver needs special handling on cold whic= h > is > > not necessary. of course, this may depends on your change of ap_startup= . > > thoughts? > > I would like to get to that, but the path on x86 is a bit messier. Ideal= ly > the order looks something like this: > > - enumerate the tree (BUS_PASS_BUS) > - reserve fixed-resources (things like acpi_sysres) (BUS_PASS_RESOURCE) > - reserve existing resources that could be moved or disabled if > their is a conflict (think PCI BARs programmed by firmware and/or > doing an initial pass of BARs) > - interrupt controllers (may need resources) (BUS_PASS_INTR) > - timers (probably need resources, need interrupts) (BUS_PASS_TIMER) > > Then all the rest. > > However, it ends up a bit messier on x86 at least. I have a WIP to at > least start doing BUS_PASS_BUS for x86, but I found that I really need > some ACPI bits to probe before the ACPI 'pcib' driver, so I've ended > up with a kind of 'BUS_PASS_PREBUS' for acpi0, and even then it turns out > that in some cases we need more granularity than just 'BUS_PASS_xxx'. > > SI_ORDER_* with ORDERED will not help as all the drivers are registered > at SI_SUB_DRIVERS during boot (which is when the SI_ORDER_* applies), > but the device tree is enumerated and attached at SI_SUB_CONFIGURE. > > And yes, the AP startup stuff is a precursor for this. > > -- > John Baldwin > --=20 -Howard
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