Re: [PATCH] bcma: fix incorrect update of BCMA_CORE_PCI_MDIO_DATA

[Larry Finger]

On 8/22/19 11:11 AM, Colin Ian King wrote:
> On 22/08/2019 17:03, Larry Finger wrote:
> > On 8/22/19 8:35 AM, Colin King wrote:
> > > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > >
> > > An earlier commit re-worked the setting of the bitmask and is now
> > > assigning v with some bit flags rather than bitwise or-ing them
> > > into v, consequently the earlier bit-settings of v are being lost.
> > > Fix this by replacing an assignment with the bitwise or instead.
> > >
> > > Addresses-Coverity: ("Unused value")
> > > Fixes: 2be25cac8402 ("bcma: add constants for PCI and use them")
> > > Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > > ---
> > >  Â drivers/bcma/driver_pci.c | 2 +-
> > >  Â 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/bcma/driver_pci.c b/drivers/bcma/driver_pci.c
> > > index f499a469e66d..d219ee947c07 100644
> > > --- a/drivers/bcma/driver_pci.c
> > > +++ b/drivers/bcma/driver_pci.c
> > > @@ -78,7 +78,7 @@ static u16 bcma_pcie_mdio_read(struct bcma_drv_pci
> > > *pc, u16 device, u8 address)
> > >  ÂÂÂÂÂÂÂÂÂ v |= (address << BCMA_CORE_PCI_MDIODATA_REGADDR_SHF_OLD);
> > >  ÂÂÂÂÂ }
> > >  Â -ÂÂÂ v = BCMA_CORE_PCI_MDIODATA_START;
> > > +ÂÂÂ v |= BCMA_CORE_PCI_MDIODATA_START;
> > >  ÂÂÂÂÂ v |= BCMA_CORE_PCI_MDIODATA_READ;
> > >  ÂÂÂÂÂ v |= BCMA_CORE_PCI_MDIODATA_TA;
> >
> > I'm not sure the "Fixes" attribute is correct.
> >
> > The changes for this section in commit 2be25cac8402 are
> >
> > -ÂÂÂÂÂÂ v = (1 << 30); /* Start of Transaction */
> > -ÂÂÂÂÂÂ v |= (1 << 28); /* Write Transaction */
> > -ÂÂÂÂÂÂ v |= (1 << 17); /* Turnaround */
> > -ÂÂÂÂÂÂ v |= (0x1F << 18);
> > +ÂÂÂÂÂÂ v = BCMA_CORE_PCI_MDIODATA_START;
> > +ÂÂÂÂÂÂ v |= BCMA_CORE_PCI_MDIODATA_WRITE;
> > +ÂÂÂÂÂÂ v |= (BCMA_CORE_PCI_MDIODATA_DEV_ADDR <<
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ BCMA_CORE_PCI_MDIODATA_DEVADDR_SHF);
> > +ÂÂÂÂÂÂ v |= (BCMA_CORE_PCI_MDIODATA_BLK_ADDR <<
> > +ÂÂÂÂÂÂÂÂÂÂÂÂ BCMA_CORE_PCI_MDIODATA_REGADDR_SHF);
> > +ÂÂÂÂÂÂ v |= BCMA_CORE_PCI_MDIODATA_TA;
> >
> > Because the code has done quite a bit of work on v just above this
> > section, I agree that this is likely an error, but that error happened
> > in an earlier commit. Thus 2be25cac8402 did not introduce the error,
> > merely copied it.
>
> Ugh, this goes back further. I didn't spot that. I'm less confident of
> what the correct settings should be now.
>
> > Has this change been tested?
>
> Afraid not, I don't have the H/W.

I admit that I looked at this only because I found it hard to believe that the 
collective wisdom of the list would have missed the usage of "=" instead of 
"|=". At least that test was passed. :)

Larry