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

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Message-ID: <20160407163443.291fbd49@xhacker>
Date:	Thu, 7 Apr 2016 16:34:43 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	Gabriele Paoloni <gabriele.paoloni@...wei.com>
CC:	"jingoohan1@...il.com" <jingoohan1@...il.com>,
	"pratyush.anand@...il.com" <pratyush.anand@...il.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"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 Gabriele,

On Thu, 7 Apr 2016 08:20:28 +0000 Gabriele Paoloni wrote:

> 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...

make sense! This commit is intend to re-setup the rc when waken from s2ram (in
s2ram state, the host lost power)

I have no good solution but to introduce one function e.g 
dw_pcie_setup_rc_after_linkup(), then move related code from dw_pcie_host_init
to it, then let my host driver resume hook to call.

Hi Pratyush, Jingoo and Bjorn etc.

any suggestions are appreciated!

Thanks,
Jisheng