linux-kernel - RE: [PATCH v2] PCI: designware: move remaining rc setup code to dw_pcie_setup

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Date:	Thu, 7 Apr 2016 08:20:28 +0000
From:	Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:	Jisheng Zhang <jszhang@...vell.com>,
	"jingoohan1@...il.com" <jingoohan1@...il.com>,
	"pratyush.anand@...il.com" <pratyush.anand@...il.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v2] PCI: designware: move remaining rc setup code to
 dw_pcie_setup_rc()

Hi Jisheng

Thanks for your reply

> -----Original Message-----
> From: Jisheng Zhang [mailto:jszhang@...vell.com]
> Sent: 07 April 2016 03:38
> To: Gabriele Paoloni; jingoohan1@...il.com; pratyush.anand@...il.com;
> bhelgaas@...gle.com
> Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org
> Subject: Re: [PATCH v2] PCI: designware: move remaining rc setup code
> to dw_pcie_setup_rc()
> 
> Hi Gabriele,
> 
> On Wed, 6 Apr 2016 14:50:29 +0000 Gabriele Paoloni wrote:
> 
> > Hi, sorry to be late on this
> >
> > > -----Original Message-----
> > > From: linux-kernel-owner@...r.kernel.org [mailto:linux-kernel-
> > > owner@...r.kernel.org] On Behalf Of Jisheng Zhang
> > > Sent: 16 March 2016 11:41
> > > To: jingoohan1@...il.com; pratyush.anand@...il.com;
> bhelgaas@...gle.com
> > > Cc: linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org; linux-
> arm-
> > > kernel@...ts.infradead.org; Jisheng Zhang
> > > Subject: [PATCH v2] PCI: designware: move remaining rc setup code
> to
> > > dw_pcie_setup_rc()
> > >
> > > dw_pcie_setup_rc(), as its name indicates, setups the RC. But
> current
> > > dw_pcie_host_init() also contains some necessary rc setup code.
> > >
> > > Another reason: the host may lost power during suspend to ram, the
> RC
> > > need to be re-setup after resume. The rc can't be correctly resumed
> > > without the rc setup code in dw_pcie_host_init().
> > >
> > > So this patch moves the code to dw_pcie_setup_rc() to address the
> above
> > > two issues. After this patch, each pcie designware driver users
> could
> > > call dw_pcie_setup_rc() to re-setup rc when resume back.
> >
> > I think this patch breaks the Hisilicon driver...
> >
> > Our driver performs linkup setup in UEFI therefore we do not call
> > dw_pcie_setup_rc(), we only call dw_pcie_host_init().
> 
> Thanks for the information. So pcie-hisi rely on UEFI to do something
> similar
> in dw_pcie_setup_rc(), this comes to a common driver implement
> question: should
> linux device driver rely on bootloader to configure HW device?

I don't see any issue with this...

> 
> Is it acceptable that pcie-hisi adds a call to dw_pcie_setup_rc() in
> hisi_add_pcie_port()?

I don't think so...that would try to overwrite what is already set by
the bootloader; so it is wrong in principle and maybe it can lead to
undefined behaviours...

Thanks

Gab

> 
> Thanks,
> Jisheng
> 
> >
> > Maybe better to group the part of code to be moved in as separate
> > function...
> >
> > Thanks and sorry for late reply.
> >
> > Gab
> >
> >