cxl/pci: Skip reset detection for DVSEC emulated decoders

HDM decoders are emulated from the DVSEC range registers in two cases:
(a) the component registers expose no HDM decoder capability, or (b) the
capability is present but the DVSEC ranges were the ones in use at driver
load.

After an FLR or SBR, __cxl_endpoint_decoder_reset_detected() reads the HDM
decoder Committed bit for every decoder marked enabled, emulated ones
included. In case (a) regs.hdm_decoder is NULL and the read oopses. In case
(b) the Committed bit was never set, so a reset gets reported that never
happened.

Use the absence of cxld->commit to elide the check for emulated decoders.

Case (b) tested under QEMU: a reset on an endpoint driven down the DVSEC
emulation path no longer reports a reset or strips the decoder flags.

Fixes: 934edcd436dc ("cxl: Add post-reset warning if reset results in loss of previously committed HDM decoders")
Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
Link: https://lore.kernel.org/linux-cxl/20260811113608.2815625-1-kanie@linux.alibaba.com/
Link: https://patch.msgid.link/20260831110449.719086-1-kanie@linux.alibaba.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
index 9d807c1a002c..43b9b7afff29 100644
--- a/drivers/cxl/core/pci.c
+++ b/drivers/cxl/core/pci.c
@@ -683,6 +683,15 @@ static int __cxl_endpoint_decoder_reset_detected(struct device *dev, void *data)
 	if ((cxld->flags & CXL_DECODER_F_ENABLE) == 0)
 		return 0;
 
+	/*
+	 * Decoders emulated from the DVSEC range registers have no commit
+	 * callback and no HDM decoder registers to consult.
+	 */
+	if (!cxld->commit) {
+		dev_warn(dev, "DVSEC emulated decode may have been cleared by reset\n");
+		return 0;
+	}
+
 	cxlhdm = dev_get_drvdata(&port->dev);
 	hdm = cxlhdm->regs.hdm_decoder;
 	ctrl = readl(hdm + CXL_HDM_DECODER0_CTRL_OFFSET(cxld->id));