[Skiboot] [PATCH] core: Add explicit 1:1 mappings in ranges properties

[Benjamin Herrenschmidt]

On Wed, 2016-02-17 at 16:18 +1100, Sam Mendoza-Jonas wrote:
> Currently skiboot adds an empty ranges property for each PCI bridge,
> representing a 1:1 mapping, which the kernel can later update if
> needed.
> However this does not appear to be the case, which leads to an issue
> in
> the kernel where the translation of assigned-addresses properties is
> mishandled and prematurely drops the PCI memory flags (ie. the first
> cell of an address).
> 
> Instead, explicitly describe a 1:1 mapping in each bridge's ranges
> property, allowing assigned-addresses to be properly handled.
> 
> Signed-off-by: Sam Mendoza-Jonas <sam at mendozajonas.com>
> ---
>  core/pci.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/core/pci.c b/core/pci.c
> index 03d5a35..3d817c7 100644
> --- a/core/pci.c
> +++ b/core/pci.c
> @@ -1321,6 +1321,15 @@ static void pci_add_one_node(struct phb *phb,
> struct pci_device *pd,
>  	uint32_t rev_class, vdid;
>  	uint32_t reg[5];
>  	uint8_t intpin;
> +	const uint32_t ranges_direct[] = {
> +				/* 32-bit direct mapping */
> +				0x02000000, 0x0, 0x0,
> +				0x02000000, 0x0, 0x0,
> +				0xf, 0x0,

0xf_00000000 doens't look like a valid 32-bit size. It should be
something like 0x1_00000000

+				/* 64-bit direct mapping */
> +				0x03000000, 0x0, 0x0,
> +				0x03000000, 0x0, 0x0,
> +				0xf, 0x0};

And here it's not enough, I thought of using 0xf0000000_00000000.

But your 64-bit range here overlaps your 32-bit one, so why not just do
a single 64-bit one ? Also put a comment saying that we know our
bridges don't cover the entire address space, so 0xf0000_* is a good
compromise.
 
>  	pci_cfg_read32(phb, pd->bdfn, 0, &vdid);
>  	pci_cfg_read32(phb, pd->bdfn, PCI_CFG_REV_ID, &rev_class);
> @@ -1414,12 +1423,12 @@ static void pci_add_one_node(struct phb *phb,
> struct pci_device *pd,
>  	 */
>  	pci_std_swizzle_irq_map(np, pd, lstate, swizzle);
>  
> -	/* We do an empty ranges property for now, we haven't setup
> any
> -	 * bridge windows, the kernel will deal with that
> -	 *
> -	 * XXX The kernel should probably fix that up
> +	/* Parts of the OF address translation in the kernel will
> fail to
> +	 * correctly translate a PCI address if translating a 1:1
> mapping
> +	 * (ie. an empty ranges property).
> +	 * Instead add a ranges property that explicitly translates
> 1:1.
>  	 */
> -	dt_add_property(np, "ranges", NULL, 0);
> +	dt_add_property(np, "ranges", ranges_direct,
> sizeof(ranges_direct));
>  
>  	list_for_each(&pd->children, child, link)
>  		pci_add_one_node(phb, child, np, lstate, swizzle);