[PATCH] drivers: pci: initialise class to 0 before reading

[Hugh Cole-Baker]

Hi Bin,

> On 1 Jan 2020, at 13:25, Bin Meng <bmeng.cn at gmail.com> wrote:
> 
> On Wed, Jan 1, 2020 at 7:15 PM Hugh Cole-Baker <sigmaris at gmail.com> wrote:
>> 
>> Otherwise, uninitialised memory from the upper 32 bits can end up in
>> find_id.class, and this causes bugs later when looking for a driver for
>> the class.
>> 
>> Signed-off-by: Hugh Cole-Baker <sigmaris at gmail.com>
>> ---
>> drivers/pci/pci-uclass.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/pci/pci-uclass.c b/drivers/pci/pci-uclass.c
>> index fab20fc60e..c28a1cc363 100644
>> --- a/drivers/pci/pci-uclass.c
>> +++ b/drivers/pci/pci-uclass.c
>> @@ -773,7 +773,7 @@ int pci_bind_bus_devices(struct udevice *bus)
>>             bdf += PCI_BDF(0, 0, 1)) {
>>                struct pci_child_platdata *pplat;
>>                struct udevice *dev;
>> -               ulong class;
>> +               ulong class = 0;
>> 
>>                if (!PCI_FUNC(bdf))
>>                        found_multi = false;
>> --
> 
> I see class is initialized in the call to:
> 
> pci_bus_read_config(bus, bdf, PCI_CLASS_REVISION, &class,
>    PCI_SIZE_32);
> class >>= 8;
> 

Maybe the driver I'm working with is doing its read_config wrongly? I'm
trying to use this Rockchip PCIe driver [1] with upstream u-boot. The
driver casts &class to u32*, uses readl() and only sets the lower 32
bits. I was assuming that this was normal for a read of PCI_SIZE_32.
However, looking at some of the other drivers, it seems like it should
be using pci_conv_32_to_size() instead?

[1] https://github.com/radxa/u-boot/blob/rk3399-pie-gms-express-baseline/drivers/pci/pcie_rockchip.c#L435

Thanks,
Hugh

> Regards,
> Bin