linux-kernel - Re: [PATCH v5 06/12] PCI: designware-ep: Make dw_pcie_ep_set

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Message-ID: <20180403125312.GA18128@e107981-ln.cambridge.arm.com>
Date:   Tue, 3 Apr 2018 13:53:12 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Niklas Cassel <nks@...wful.org>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Niklas Cassel <niklas.cassel@...s.com>,
        cyrille.pitchen@...e-electrons.com,
        Jingoo Han <jingoohan1@...il.com>,
        Joao Pinto <Joao.Pinto@...opsys.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Niklas Cassel <niklass@...s.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 06/12] PCI: designware-ep: Make dw_pcie_ep_set_bar()
 handle 64-bit BARs properly

On Mon, Apr 02, 2018 at 09:37:03PM +0200, Niklas Cassel wrote:
> On Thu, Mar 29, 2018 at 03:17:11PM +0530, Kishon Vijay Abraham I wrote:
> > Hi,
> > 
> > On Wednesday 28 March 2018 05:20 PM, Niklas Cassel wrote:
> > > Since a 64-bit BAR consists of a BAR pair, we need to write to both
> > > BARs in the BAR pair to setup the BAR properly.
> > > 
> > > Signed-off-by: Niklas Cassel <niklas.cassel@...s.com>
> > > ---
> > >  drivers/pci/dwc/pcie-designware-ep.c | 11 +++++++++--
> > >  1 file changed, 9 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/pci/dwc/pcie-designware-ep.c b/drivers/pci/dwc/pcie-designware-ep.c
> > > index 5a0bb53c795c..571b90f88d84 100644
> > > --- a/drivers/pci/dwc/pcie-designware-ep.c
> > > +++ b/drivers/pci/dwc/pcie-designware-ep.c
> > > @@ -138,8 +138,15 @@ static int dw_pcie_ep_set_bar(struct pci_epc *epc, u8 func_no,
> > >  		return ret;
> > >  
> > >  	dw_pcie_dbi_ro_wr_en(pci);
> > > -	dw_pcie_writel_dbi2(pci, reg, size - 1);
> > > -	dw_pcie_writel_dbi(pci, reg, flags);
> > > +	if (flags & PCI_BASE_ADDRESS_MEM_TYPE_64) {
> > > +		dw_pcie_writel_dbi2(pci, reg, lower_32_bits(size - 1));
> > > +		dw_pcie_writel_dbi(pci, reg, flags);
> > > +		dw_pcie_writel_dbi2(pci, reg + 4, upper_32_bits(size - 1));
> > > +		dw_pcie_writel_dbi(pci, reg + 4, 0);
> > > +	} else {
> > > +		dw_pcie_writel_dbi2(pci, reg, size - 1);
> > > +		dw_pcie_writel_dbi(pci, reg, flags);
> > > +	}
> > 
> > 
> > I think this should work too?
> > 	dw_pcie_writel_dbi2(pci, reg, lower_32_bits(size - 1));
> > 	dw_pcie_writel_dbi(pci, reg, flags);
> > 
> > 	if (flags & PCI_BASE_ADDRESS_MEM_TYPE_64) {
> > 		dw_pcie_writel_dbi2(pci, reg + 4, upper_32_bits(size - 1));
> > 		dw_pcie_writel_dbi(pci, reg + 4, 0);
> > 	}
> > 
> 
> Hello Kishon,
> 
> I agree, your suggestion is more neat.
> 
> 
> Kishon, please tell me if you insist that the long if-statement
> in pci_epc_set_bar() should be split, since there are 5 different
> conditions. Because imho, having 5 succeeding if-statements isn't
> clearer than having 1 long if-statement.
> 
> If Kishon agrees with me, then the review comment in this mail
> seems to be the only review comment.
> And in that case, perhaps Lorenzo wouldn't mind fixing this up.
> Or perhaps Lorenzo prefers if I reroll the whole patch series?

I updated it myself in my pci/endpoint branch, please have a look, I
can't guarantee we can merge this for this cycle though, I will ask
Bjorn; apologies I could not be online for a while.

Lorenzo

> Kind regards,
> Niklas