linux-kernel - Re: [PATCH] PCI: qcom: Fix warning generated due to the incorrect data type

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Message-ID: <20211130160338.GA2739234@bhelgaas>
Date:   Tue, 30 Nov 2021 10:03:38 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc:     lorenzo.pieralisi@....com, bhelgaas@...gle.com,
        svarbanov@...sol.com, bjorn.andersson@...aro.org, robh@...nel.org,
        linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>,
        Marc Zyngier <maz@...nel.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Sven Peter <sven@...npeter.dev>
Subject: Re: [PATCH] PCI: qcom: Fix warning generated due to the incorrect
 data type

[+cc Marc, Alyssa, Sven for RID-to-SID mapping insight.  The patch at
https://lore.kernel.org/all/20211130062137.GD205712@thinkpad/ merely
fixes a warning.  My meta-question is about the qcom BDF-to-SID
mapping.]

On Tue, Nov 30, 2021 at 11:51:37AM +0530, Manivannan Sadhasivam wrote:
> On Mon, Nov 29, 2021 at 09:36:14PM -0600, Bjorn Helgaas wrote:
> > ...
> > I'm also curious why pcie-qcom.c is the only driver that does this.
> > "iommu-map" is not specific to qcom, but no other drivers do similar
> > things with it.
> 
> Yes, on the recent qcom platforms starting from sm8250 we need to program
> the BDF to SID mapping in the controller and that's the reason we are
> extracting the "iommu-map" property in DT.

This sounds like something that may not really be specific to sm8250.

It looks vaguely similar to apple_pcie_add_device().  Compare the qcom
code at [1] with the Apple code at [2].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/dwc/pcie-qcom.c?id=v5.16-rc1#n1308
[2] https://git.kernel.org/linus/468c8d52c332

> > > sparse warnings: (new ones prefixed by >>)
> > > >> drivers/pci/controller/dwc/pcie-qcom.c:1305:30: sparse: sparse: incorrect type in initializer (different base types) @@     expected unsigned short [usertype] bdf_be @@     got restricted __be16 [usertype] @@
> > >    drivers/pci/controller/dwc/pcie-qcom.c:1305:30: sparse:     expected unsigned short [usertype] bdf_be
> > >    drivers/pci/controller/dwc/pcie-qcom.c:1305:30: sparse:     got restricted __be16 [usertype]
> > > 
> > > Reported-by: kernel test robot <lkp@...el.com>
> > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-qcom.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> > > index 8a7a300163e5..6c3b034e9946 100644
> > > --- a/drivers/pci/controller/dwc/pcie-qcom.c
> > > +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> > > @@ -1312,7 +1312,7 @@ static int qcom_pcie_config_sid_sm8250(struct qcom_pcie *pcie)
> > >  
> > >  	/* Look for an available entry to hold the mapping */
> > >  	for (i = 0; i < nr_map; i++) {
> > > -		u16 bdf_be = cpu_to_be16(map[i].bdf);
> > > +		__be16 bdf_be = cpu_to_be16(map[i].bdf);
> > >  		u32 val;
> > >  		u8 hash;
> > >  
> > > -- 
> > > 2.25.1
> > >