From 6aa41144e7f1a624062f1e66a4744c168ade1f31 Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Mon, 6 Jun 2022 13:32:01 -0700 Subject: [PATCH] cxl/acpi: Add a host-bridge index lookup mechanism 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 Link: https://lore.kernel.org/r/20220624041950.559155-14-dan.j.williams@intel.com Signed-off-by: Dan Williams --- 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 ff6ea869fcc9..1bec38385a71 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 5e84aa2d09e2..8f39cfb0d972 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; };