On Sat, Apr 30, 2022 at 04:48:43PM +0800, Huacai Chen wrote:
> On LS2K/LS7A, some unexisting devices don't return 0xffffffff when
> scanning. This is a hardware flaw but we can only avoid it by software
> now.
s/unexisting/non-existant/ (many occurrences: subject line, commit
log, comments below)
What happens in other situations that normally cause Unsupported
Request or similar errors? For example, memory reads/writes to a
device in D3hot should cause an Unsupported Request error. I'm
wondering whether other error handling assumptions might be broken
on LS2K/LS7A.
> Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> ---
> drivers/pci/controller/pci-loongson.c | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
> index adbfa4a2330f..48316daa1f23 100644
> --- a/drivers/pci/controller/pci-loongson.c
> +++ b/drivers/pci/controller/pci-loongson.c
> @@ -138,6 +138,8 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
> int where)
> {
> unsigned char busnum = bus->number;
> + unsigned int device = PCI_SLOT(devfn);
> + unsigned int function = PCI_FUNC(devfn);
> struct loongson_pci *priv = pci_bus_to_loongson_pci(bus);
>
> if (pci_is_root_bus(bus))
> @@ -147,8 +149,13 @@ static void __iomem *pci_loongson_map_bus(struct pci_bus *bus, unsigned int devf
> * Do not read more than one device on the bus other than
> * the host bus. For our hardware the root bus is always bus 0.
> */
> - if (priv->data->flags & FLAG_DEV_FIX &&
> - !pci_is_root_bus(bus) && PCI_SLOT(devfn) > 0)
> + if ((priv->data->flags & FLAG_DEV_FIX) && bus->self) {
> + if (!pci_is_root_bus(bus) && (device > 0))
> + return NULL;
> + }
> +
> + /* Don't access unexisting devices */
> + if (pci_is_root_bus(bus) && (device >= 9 && device <= 20 && function > 0))
Yuck. This is pretty nasty magic. If this is something that might be
fixed in future versions of the hardware, maybe you should factor this
out into a function pointer in loongson_pci_data or something.
> return NULL;
>
> /* CFG0 can only access standard space */
> --
> 2.27.0
>
