The ACPI CXL Fixed Memory Window Structure (CFMWS) defines multiple methods to determine which host bridge provides access to a given endpoint relative to that device's position in the interleave. The "Interleave Arithmetic" defines either a "standard modulo" / round-random algorithm, or "xormap" based algorithm which can be defined as a non-linear transform. Given that there are already more options beyond "standard modulo" and that "xormap" may turn out to be ACPI CXL specific, provide a callback for the region provisioning code to map endpoint positions back to expected host bridge id (cxl_dport target).
For now just support the simple modulo math case and save the xormap for a follow-on change. Reviewed-by: Jonathan Cameron <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Dan Williams <[email protected]> --- drivers/cxl/core/port.c | 16 ++++++++++++++++ drivers/cxl/cxl.h | 2 ++ 2 files changed, 18 insertions(+) diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c index bd0673821d28..2f0b47db53da 100644 --- a/drivers/cxl/core/port.c +++ b/drivers/cxl/core/port.c @@ -1421,6 +1421,20 @@ static int decoder_populate_targets(struct cxl_switch_decoder *cxlsd, return rc; } +static struct cxl_dport *cxl_hb_modulo(struct cxl_root_decoder *cxlrd, int pos) +{ + struct cxl_switch_decoder *cxlsd = &cxlrd->cxlsd; + struct cxl_decoder *cxld = &cxlsd->cxld; + int iw; + + iw = cxld->interleave_ways; + if (dev_WARN_ONCE(&cxld->dev, iw != cxlsd->nr_targets, + "misconfigured root decoder\n")) + return NULL; + + return cxlrd->cxlsd.target[pos % iw]; +} + static struct lock_class_key cxl_decoder_key; /** @@ -1510,6 +1524,8 @@ struct cxl_root_decoder *cxl_root_decoder_alloc(struct cxl_port *port, return ERR_PTR(rc); } + cxlrd->calc_hb = cxl_hb_modulo; + cxld = &cxlsd->cxld; cxld->dev.type = &cxl_decoder_root_type; /* diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h index 95d74cf425a4..cd81e642e900 100644 --- a/drivers/cxl/cxl.h +++ b/drivers/cxl/cxl.h @@ -322,11 +322,13 @@ struct cxl_switch_decoder { * struct cxl_root_decoder - Static platform CXL address decoder * @res: host / parent resource for region allocations * @region_id: region id for next region provisioning event + * @calc_hb: which host bridge covers the n'th position by granularity * @cxlsd: base cxl switch decoder */ struct cxl_root_decoder { struct resource *res; atomic_t region_id; + struct cxl_dport *(*calc_hb)(struct cxl_root_decoder *cxlrd, int pos); struct cxl_switch_decoder cxlsd; };
