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.
I merged this from Lorenzo's branch, but I updated the commit log like
this because the undefined behavior is the real problem:
PCI: tegra194: Fix tegra_pcie_ep_raise_msi_irq() ill-defined shift
tegra_pcie_ep_raise_msi_irq() shifted a signed 32-bit value left by 31
bits. The behavior of this is implementation-defined.
Replace the shift by BIT(), which is well-defined.
Found by cppcheck:
$ 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);
^
[bhelgaas: commit log]
Link: https://lore.kernel.org/r/20210618160219.303092-1-jonathanh@xxxxxxxxxx
Fixes: c57247f940e8 ("PCI: tegra: Add support for PCIe endpoint mode in Tegra194")
Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> > Fixes: c57247f940e8 PCI: tegra: Add support for PCIe endpoint mode in Tegra194
> > Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> > ---
> > 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
> >
