[PATCH] cxl: Allow PSL timebase to not sync

[Frederic Barrat]

CXL driver synchronizes the PSL timebase with the CAPP during
initialization. If it can't synchronize, then the driver currently
fails and the cxl adapter is not usable. That behavior is a bit
extreme for the time being, as some adapters are known to have
troubles syncing their PSL timebase and there are no known use of it.

Introduce a psl_timebase module parameter to control whether PSL
timebase is required or not. Default is to allow initializaton even if
syncing failed.
Default behavior will be changed when current issues with some cxl
adapters are resolved.

Signed-off-by: Frederic Barrat <fbarrat at linux.vnet.ibm.com>
---
 drivers/misc/cxl/cxl.h  | 1 +
 drivers/misc/cxl/main.c | 4 ++++
 drivers/misc/cxl/pci.c  | 7 +++++--
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index a521bc7..c67f2c2 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -27,6 +27,7 @@
 #include <uapi/misc/cxl.h>
 
 extern uint cxl_verbose;
+extern uint cxl_psl_timebase;
 
 #define CXL_TIMEOUT 5
 
diff --git a/drivers/misc/cxl/main.c b/drivers/misc/cxl/main.c
index 9fde75e..2915c59 100644
--- a/drivers/misc/cxl/main.c
+++ b/drivers/misc/cxl/main.c
@@ -32,6 +32,10 @@ uint cxl_verbose;
 module_param_named(verbose, cxl_verbose, uint, 0600);
 MODULE_PARM_DESC(verbose, "Enable verbose dmesg output");
 
+uint cxl_psl_timebase;
+module_param_named(psl_timebase, cxl_psl_timebase, uint, 0600);
+MODULE_PARM_DESC(psl_timebase, "Require PSL timebase synchronization");
+
 static inline void _cxl_slbia(struct cxl_context *ctx, struct mm_struct *mm)
 {
 	struct task_struct *task;
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 0c6c17a1..3360cdd 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1189,8 +1189,11 @@ static int cxl_configure_adapter(struct cxl *adapter, struct pci_dev *dev)
 	if ((rc = pnv_phb_to_cxl_mode(dev, OPAL_PHB_CAPI_MODE_SNOOP_ON)))
 		goto err;
 
-	if ((rc = cxl_setup_psl_timebase(adapter, dev)))
-		goto err;
+	if ((rc = cxl_setup_psl_timebase(adapter, dev))) {
+		if (cxl_psl_timebase)
+			goto err;
+		pr_err("PSL: Timebase sync: ignoring error\n");
+	}
 
 	if ((rc = cxl_register_psl_err_irq(adapter)))
 		goto err;
-- 
1.9.1