Re: [PATCH] PCI: tegra: Fix shiftTooManyBitsSigned warning for Tegra194

[Bjorn Helgaas <helgaas@kernel.org>]

On Wed, Jun 23, 2021 at 09:52:14AM +0100, Lorenzo Pieralisi wrote:
> On Fri, Jun 18, 2021 at 06:04:28PM -0500, Bjorn Helgaas wrote:
> > On Fri, Jun 18, 2021 at 05:02:19PM +0100, Jon Hunter wrote:
> > > The cppcheck tool issues the following warning for the Tegra194 PCIe
> > > driver ...
> > > 
> > >  $ cppcheck --enable=all drivers/pci/controller/dwc/pcie-tegra194.c
> > >  Checking drivers/pci/controller/dwc/pcie-tegra194.c ...
> > > 
> > >  drivers/pci/controller/dwc/pcie-tegra194.c:1829:23: portability:
> > > 	Shifting signed 32-bit value by 31 bits is
> > > 	implementation-defined behaviour. See condition at line 1826.
> > > 	[shiftTooManyBitsSigned]
> > > 
> > >   appl_writel(pcie, (1 << irq), APPL_MSI_CTRL_1);
> > >                       ^
> > > The above warning occurs because the '1' is treated as a signed type
> > > and so fix this by using the 'BIT' macro to ensure that this is defined
> > > as a unsigned type.
> > 
> > The subject and commit log should describe the problem we're fixing.
> > The *warning* is not the problem; the problem is the undefined
> > behavior.
> > 
> > I'll fix this up, no need to repost for this.
> 
> Hi Bjorn,
> 
> I can fix it up myself, just wanted to ask if you merged it already, it
> does not look like but I thought I'd check.

Oops, sorry, I guess I dropped the ball on this one and didn't get it
merged.  When you do, can you update the subject as well, e.g.,

  s/PCI: tegra/PCI: tegra194/

to differentiate from the other "tegra" driver?

> > > Fixes: c57247f940e8 PCI: tegra: Add support for PCIe endpoint mode in Tegra194
> > > Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-tegra194.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/pci/controller/dwc/pcie-tegra194.c b/drivers/pci/controller/dwc/pcie-tegra194.c
> > > index 8fc08336f76e..3c1feeab104f 100644
> > > --- a/drivers/pci/controller/dwc/pcie-tegra194.c
> > > +++ b/drivers/pci/controller/dwc/pcie-tegra194.c
> > > @@ -1826,7 +1826,7 @@ static int tegra_pcie_ep_raise_msi_irq(struct tegra_pcie_dw *pcie, u16 irq)
> > >  	if (unlikely(irq > 31))
> > >  		return -EINVAL;
> > >  
> > > -	appl_writel(pcie, (1 << irq), APPL_MSI_CTRL_1);
> > > +	appl_writel(pcie, BIT(irq), APPL_MSI_CTRL_1);
> > >  
> > >  	return 0;
> > >  }
> > > -- 
> > > 2.25.1
> > >