[PATCH 0/6] Description for PCI patches using platform driver

[Bhushan Bharat-R65777]

Hello Ben, Kumar, others

Please provide your comments/thoughts on this ?

Thanks
-Bharat

> > > >
> > > > > -----Original Message-----
> > > > > From: Jia Hongtao-B38951
> > > > > Sent: Friday, June 08, 2012 3:12 PM
> > > > > To: linuxppc-dev at lists.ozlabs.org; galak at kernel.crashing.org
> > > > > Cc: Li Yang-R58472; benh at kernel.crashing.org; Wood Scott-B07421;
> > > > Bhushan Bharat-
> > > > > R65777; Jia Hongtao-B38951
> > > > > Subject: [PATCH 0/6] Description for PCI patches using platform
> > > > > driver
> > > > >
> > > > > This series of patches are to unify pci initialization code and
> > > > > add PM
> > > > support
> > > > > for all 85xx/86xx powerpc boards. But two side effects are
> > > > > introduced
> > > > by this
> > > > > mechanism which listed below:
> > > > >
> > > > > 1. of_platform_bus_probe() will be called twice but in some
> > > > > cases
> > > > duplication
> > > > >    warning occured. We fix this in [PATCH 5/6].
> > > > >
> > > > > 2. Edac driver failed to register pci nodes as platform devices.
> > > > > We fix
> > > > this
> > > > >    in [PATCH 6/6].
> > > >
> > > > With these patches will not the SWIOTLB will not be initialized
> > > > even if PCI/PCIe demanded?
> > > >
> > > > Thanks
> > > > -Bharat
> > > >
> > >
> > > These patches still have the swiotlb init problem if
> > "ppc_swiotlb_enable" is
> > > only demanded by PCI/PCIe. One of the purposes of sending out these
> > patches is
> > > to let us start a discussion for this problem in upstream.
> >
> > Ok, I did not find any mention of that, so I thought that you have
> > resolved the issue by some means in these patches which I did not catch.
> >
> > So, these patches introduces the issue, that SWIOTLB will not be
> > initialized if requested by pci/pcie. The request is raised by setting
> > the flag ppc_swiotlb_enable. The swiotlb_init() will be called in
> > mem_init() if ppc_swiotlb_enable is set. Now with these patches, the
> > request is raised after mem_init() is called. So request not handled :).
> >
> > Following are the solutions we have thought of during our internal
> > discussions (if I did not missed any):
> >
> > 1. These patches move the code from platform init to device init
> > (arch_initcall()). Rather than moving the whole code, let us divide
> > the code into two. First, which is needed to raise the swiotlb init
> > request and second the rest. Define this first as an function in
> > arch/powerpc/sysdev/fsl_pci.c and call this from platform init code of
> > the SOCs.
> >
> > 2. All known devices, the lowest PCIe outbound range starts at
> > 0x80000000, but there's nothing above 0xc0000000. So the inbound of
> > size 0x8000_0000 is always availbe on all devices. Hardcode the check
> > in platform code to check memblock_end_of_DRAM() to 0x80000000.
> >
> > Something like this:
> >
> > diff --git a/arch/powerpc/platforms/85xx/corenet_ds.c
> > b/arch/powerpc/platforms/85xx/corenet_ds.c
> > index 1f7028e..ef4e215 100644
> > --- a/arch/powerpc/platforms/85xx/corenet_ds.c
> > +++ b/arch/powerpc/platforms/85xx/corenet_ds.c
> > @@ -79,7 +79,7 @@ void __init corenet_ds_setup_arch(void)  #endif
> >
> > #ifdef CONFIG_SWIOTLB
> > -       if (memblock_end_of_DRAM() > 0xffffffff)
> > +       if (memblock_end_of_DRAM() > 0xff000000)
> >                  ppc_swiotlb_enable = 1;  #endif
> >          pr_info("%s board from Freescale Semiconductor\n",
> > ppc_md.name);
> >
> > -------------
> >
> > 3. Always do swiotlb_init() in mem_init() and later after PCI init, if
> > the swiotlb is not needed then free it (swiotlb_free()).
> >
> > 4. etc, please provide some other better way.
> >
> > Thanks
> > -Bharat
> 
> Thanks.
> In my point of view the 2nd solution is better for it does not treat PCI/PCIe as
> the special kind of devices from others.
> 
> -Jia Hongtao.