diff mbox series

[v2,3/4] cxl/region: Verify target positions using the ordered target list

Message ID 562c5e2097f32567bf7aa505d7952d9c068d830b.1715192606.git.alison.schofield@intel.com
State Superseded
Headers show
Series XOR Math Fixups: translation & position | expand

Commit Message

Alison Schofield May 8, 2024, 6:47 p.m. UTC 
From: Alison Schofield <alison.schofield@intel.com>

When a root decoder is configured the interleave target list is read
from the BIOS populated CFMWS structure. Per the CXL spec 3.1 Table
9-22 the target list is in interleave order. The CXL driver populates
its decoder target list in the same order and stores it in 'struct
cxl_switch_decoder' field "@target: active ordered target list in
current decoder configuration"

Given the promise of an ordered list, the driver can stop duplicating
the work of BIOS and simply check target positions against the ordered
list during region configuration.

The simplified check against the ordered list is presented here.
A follow-on patch will remove the unused code.

For Modulo arithmetic this is not a fix, only a simplification.
For XOR arithmetic this is a fix for HB IW of 3,6,12.

Fixes: f9db85bfec0d ("cxl/acpi: Support CXL XOR Interleave Math (CXIMS)")
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---
 drivers/cxl/core/region.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Jonathan Cameron June 7, 2024, 3:04 p.m. UTC | #1 
On Wed,  8 May 2024 11:47:52 -0700
alison.schofield@intel.com wrote:

> From: Alison Schofield <alison.schofield@intel.com>
> 
> When a root decoder is configured the interleave target list is read
> from the BIOS populated CFMWS structure. Per the CXL spec 3.1 Table
> 9-22 the target list is in interleave order. The CXL driver populates
> its decoder target list in the same order and stores it in 'struct
> cxl_switch_decoder' field "@target: active ordered target list in
> current decoder configuration"
> 
> Given the promise of an ordered list, the driver can stop duplicating
> the work of BIOS and simply check target positions against the ordered
> list during region configuration.
> 
> The simplified check against the ordered list is presented here.
> A follow-on patch will remove the unused code.
> 
> For Modulo arithmetic this is not a fix, only a simplification.
> For XOR arithmetic this is a fix for HB IW of 3,6,12.
> 
> Fixes: f9db85bfec0d ("cxl/acpi: Support CXL XOR Interleave Math (CXIMS)")
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Dan Williams June 11, 2024, 9:50 p.m. UTC | #2 
alison.schofield@ wrote:
> From: Alison Schofield <alison.schofield@intel.com>
> 
> When a root decoder is configured the interleave target list is read
> from the BIOS populated CFMWS structure. Per the CXL spec 3.1 Table
> 9-22 the target list is in interleave order. The CXL driver populates
> its decoder target list in the same order and stores it in 'struct
> cxl_switch_decoder' field "@target: active ordered target list in
> current decoder configuration"
> 
> Given the promise of an ordered list, the driver can stop duplicating
> the work of BIOS and simply check target positions against the ordered
> list during region configuration.
> 
> The simplified check against the ordered list is presented here.
> A follow-on patch will remove the unused code.
> 
> For Modulo arithmetic this is not a fix, only a simplification.
> For XOR arithmetic this is a fix for HB IW of 3,6,12.
> 
> Fixes: f9db85bfec0d ("cxl/acpi: Support CXL XOR Interleave Math (CXIMS)")
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>

LGTM

Reviewed-by: Dan Williams <dan.j.williams@intel.com>
diff mbox series

Patch

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 2fe93c5a8072..6aa2c981f1c4 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1559,10 +1559,13 @@  static int cxl_region_attach_position(struct cxl_region *cxlr,
 				      const struct cxl_dport *dport, int pos)
 {
 	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_switch_decoder *cxlsd = &cxlrd->cxlsd;
+	struct cxl_decoder *cxld = &cxlsd->cxld;
+	int iw = cxld->interleave_ways;
 	struct cxl_port *iter;
 	int rc;
 
-	if (cxlrd->calc_hb(cxlrd, pos) != dport) {
+	if (dport != cxlrd->cxlsd.target[pos % iw]) {
 		dev_dbg(&cxlr->dev, "%s:%s invalid target position for %s\n",
 			dev_name(&cxlmd->dev), dev_name(&cxled->cxld.dev),
 			dev_name(&cxlrd->cxlsd.cxld.dev));