Re: [PATCH] PCI: aardvark: fix big endian support

[Russell King - ARM Linux admin <linux@armlinux.org.uk>]

On Mon, Jul 15, 2019 at 05:08:40PM +0200, Thomas Petazzoni wrote:
> Hello Grzegorz,
> 
> Thanks for this work. I indeed never tested this code on BE platforms,
> and it is very possible that I overlooked endianness issues, so thanks
> for having a look at this and proposing some patches. See some
> questions/comments below.
> 
> On Mon, 15 Jul 2019 16:15:22 +0200
> Grzegorz Jaszczyk <jaz@semihalf.com> wrote:
> 
> > Initialise every not-byte wide fields of emulated pci bridge config
> > space with proper cpu_to_le* macro. This is required since the structure
> > describing config space of emulated bridge assumes little-endian
> > convention.
> > 
> > Signed-off-by: Grzegorz Jaszczyk <jaz@semihalf.com>
> > ---
> >  drivers/pci/controller/pci-aardvark.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
> > index 134e030..06a12749 100644
> > --- a/drivers/pci/controller/pci-aardvark.c
> > +++ b/drivers/pci/controller/pci-aardvark.c
> > @@ -479,8 +479,10 @@ static void advk_sw_pci_bridge_init(struct advk_pcie *pcie)
> >  {
> >  	struct pci_bridge_emul *bridge = &pcie->bridge;
> >  
> > -	bridge->conf.vendor = advk_readl(pcie, PCIE_CORE_DEV_ID_REG) & 0xffff;
> > -	bridge->conf.device = advk_readl(pcie, PCIE_CORE_DEV_ID_REG) >> 16;
> > +	bridge->conf.vendor =
> > +		cpu_to_le16(advk_readl(pcie, PCIE_CORE_DEV_ID_REG) & 0xffff);
> > +	bridge->conf.device =
> > +		cpu_to_le16(advk_readl(pcie, PCIE_CORE_DEV_ID_REG) >> 16);
> >  	bridge->conf.class_revision =
> >  		advk_readl(pcie, PCIE_CORE_DEV_REV_REG) & 0xff;
> 
> So conf.vendor and conf.device and stored as little-endian in the
> emulated config address space, but conf.class_revision is stored in the
> CPU endianness ?
> 
> >  
> > @@ -489,8 +491,8 @@ static void advk_sw_pci_bridge_init(struct advk_pcie *pcie)
> >  	bridge->conf.iolimit = PCI_IO_RANGE_TYPE_32;
> 
> >  
> >  	/* Support 64 bits memory pref */
> > -	bridge->conf.pref_mem_base = PCI_PREF_RANGE_TYPE_64;
> > -	bridge->conf.pref_mem_limit = PCI_PREF_RANGE_TYPE_64;
> > +	bridge->conf.pref_mem_base = cpu_to_le16(PCI_PREF_RANGE_TYPE_64);
> > +	bridge->conf.pref_mem_limit = cpu_to_le16(PCI_PREF_RANGE_TYPE_64);
> 
> Same here: why are conf.pref_mem_{base,limit} converted to LE, but not
> conf.iolimit ?
> 
> Also, the advk_pci_bridge_emul_pcie_conf_read() and
> advk_pci_bridge_emul_pcie_conf_write() return values that are in the
> CPU endianness.
> 
> Am I missing something ?

Getting the types correct and then using Sparse to validate the code
will help to identify issues exactly like this.

-- 
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