On Wed, Jan 29, 2020 at 02:54:19PM +1100, Oliver O'Halloran wrote:
> On Wed, Jan 29, 2020 at 2:09 PM David Gibson
> <da...@gibson.dropbear.id.au> wrote:
> >
> > On Mon, Jan 27, 2020 at 03:45:05PM +0100, Cédric Le Goater wrote:
> > > From: Benjamin Herrenschmidt <b...@kernel.crashing.org>
> > >
>
> *snip*
>
> > > +
> > > +/*
> > > + * The CONFIG_DATA register expects little endian accesses, but as the
> > > + * region is big endian, we have to swap the value.
> > > + */
> > > +static void pnv_phb4_config_write(PnvPHB4 *phb, unsigned off,
> > > + unsigned size, uint64_t val)
> > > +{
> > > + uint32_t cfg_addr, limit;
> > > + PCIDevice *pdev;
> > > +
> > > + pdev = pnv_phb4_find_cfg_dev(phb);
> > > + if (!pdev) {
> > > + return;
> > > + }
> > > + cfg_addr = (phb->regs[PHB_CONFIG_ADDRESS >> 3] >> 32) & 0xffc;
> > > + cfg_addr |= off;
> > > + limit = pci_config_size(pdev);
> > > + if (limit <= cfg_addr) {
> > > + /*
> > > + * conventional pci device can be behind pcie-to-pci bridge.
> > > + * 256 <= addr < 4K has no effects.
> > > + */
> > > + return;
> > > + }
> > > + switch (size) {
> > > + case 1:
> > > + break;
> > > + case 2:
> > > + val = bswap16(val);
> >
> > I'm a little confused by these byteswaps. As I see below the device
> > is set to big endian, so the values passed in here should already be
> > in host-native endian. Why do you need the swap? Are some of the
> > registers in the bank BE and some LE?
>
> All the registers are BE except for CONFIG_DATA, which isn't actually
> a register. It's really a window into the config space of the device
> specified in CONFIG_ADDR so it doesn't do any byte-swapping.
Ah, right, that makes sense.
>
> > > + break;
> > > + case 4:
> > > + val = bswap32(val);
> > > + break;
> > > + default:
> > > + g_assert_not_reached();
> > > + }
> > > + pci_host_config_write_common(pdev, cfg_addr, limit, val, size);
> > > +}
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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