[PATCH V6] cxl: Fix timebase synchronization status on P9

[Christophe Lombard]

The PSL Timebase register is updated by the PSL to maintain the
timebase.
On P9, the Timebase value is only provided by the CAPP as received
the last time a timebase request was performed.
The timebase requests are initiated through the adapter configuration or
application registers.
The specific sysfs entry "/sys/class/cxl/cardxx/psl_timebase_synced" is
now dynamically updated according the content of the PSL Timebase
register.

Signed-off-by: Christophe Lombard <clombard at linux.vnet.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>

---
This patch applies on top of this patch:
 http://patchwork.ozlabs.org/patch/873663/

Changelog[v6]
 - Rebased to latest upstream.
 - Recompute the status only in native mode.

Changelog[v5]
 - Rebased to latest upstream.
 - Changed the type of 'delta'

Changelog[v4]
 - Rebased to latest upstream.
 - Added log message.

Changelog[v3]
 - Rebased to latest upstream.
 - Dynamic update is now applied to P8.

Changelog[v2]
 - Missing Signed-off-by.
 - Spaces required around the ':'.
---
 drivers/misc/cxl/pci.c   | 17 -----------------
 drivers/misc/cxl/sysfs.c | 12 ++++++++++++
 2 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 66eed6a..3247eaf 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -606,9 +606,6 @@ static u64 timebase_read_xsl(struct cxl *adapter)
 
 static void cxl_setup_psl_timebase(struct cxl *adapter, struct pci_dev *dev)
 {
-	u64 psl_tb;
-	int delta;
-	unsigned int retry = 0;
 	struct device_node *np;
 
 	adapter->psl_timebase_synced = false;
@@ -636,20 +633,6 @@ static void cxl_setup_psl_timebase(struct cxl *adapter, struct pci_dev *dev)
 	cxl_p1_write(adapter, CXL_PSL_Control, 0x0000000000000000);
 	cxl_p1_write(adapter, CXL_PSL_Control, CXL_PSL_Control_tb);
 
-	/* Wait until CORE TB and PSL TB difference <= 16usecs */
-	do {
-		msleep(1);
-		if (retry++ > 5) {
-			dev_info(&dev->dev, "PSL timebase can't synchronize\n");
-			return;
-		}
-		psl_tb = adapter->native->sl_ops->timebase_read(adapter);
-		delta = mftb() - psl_tb;
-		if (delta < 0)
-			delta = -delta;
-	} while (tb_to_ns(delta) > 16000);
-
-	adapter->psl_timebase_synced = true;
 	return;
 }
 
diff --git a/drivers/misc/cxl/sysfs.c b/drivers/misc/cxl/sysfs.c
index a8b6d6a..95285b7 100644
--- a/drivers/misc/cxl/sysfs.c
+++ b/drivers/misc/cxl/sysfs.c
@@ -62,7 +62,19 @@ static ssize_t psl_timebase_synced_show(struct device *device,
 					char *buf)
 {
 	struct cxl *adapter = to_cxl_adapter(device);
+	u64 psl_tb, delta;
 
+	/* Recompute the status only in native mode */
+	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+		psl_tb = adapter->native->sl_ops->timebase_read(adapter);
+		delta = abs(mftb() - psl_tb);
+
+		/* CORE TB and PSL TB difference <= 16usecs ? */
+		adapter->psl_timebase_synced = (tb_to_ns(delta) < 16000) ? true : false;
+		pr_devel("PSL timebase %s - delta: 0x%016llx\n",
+			 (tb_to_ns(delta) < 16000) ? "synchronized" :
+			 "not synchronized", tb_to_ns(delta));
+	}
 	return scnprintf(buf, PAGE_SIZE, "%i\n", adapter->psl_timebase_synced);
 }
 
-- 
2.7.4