cxl: Check if PSL data-cache is available before issue flush request

PSL9D doesn't have a data-cache that needs to be flushed before
resetting the card. However when cxl tries to flush data-cache on such
a card, it times-out as PSL_Control register never indicates flush
operation complete due to missing data-cache. This is usually
indicated in the kernel logs with this message:

"WARNING: cache flush timed out"

To fix this the patch checks PSL_Debug register CDC-Field(BIT:27)
which indicates the absence of a data-cache and sets a flag
'no_data_cache' in 'struct cxl_native' to indicate this. When
cxl_data_cache_flush() is called it checks the flag and if set bails
out early without requesting a data-cache flush operation to the PSL.

Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 13 insertions, 6 deletions

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 9bc30c20b66b..35f486912ddc 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -456,6 +456,7 @@ static int init_implementation_adapter_regs_psl9(struct cxl *adapter,
         u64 chipid;
         u32 phb_index;
         u64 capp_unit_id;
+        u64 psl_debug;
         int rc;
 
         rc = cxl_calc_capp_routing(dev, &chipid, &phb_index, &capp_unit_id);
@@ -510,6 +511,16 @@ static int init_implementation_adapter_regs_psl9(struct cxl *adapter,
                 cxl_p1_write(adapter, CXL_PSL9_DEBUG, 0xC000000000000000ULL);
         }
 
+        /*
+         * Check if PSL has data-cache. We need to flush adapter datacache
+         * when as its about to be removed.
+         */
+        psl_debug = cxl_p1_read(adapter, CXL_PSL9_DEBUG);
+        if (psl_debug & CXL_PSL_DEBUG_CDC) {
+                dev_dbg(&dev->dev, "No data-cache present\n");
+                adapter->native->no_data_cache = true;
+        }
+
         return 0;
 }
 
@@ -1448,10 +1459,8 @@ int cxl_pci_reset(struct cxl *adapter)
 
         /*
          * The adapter is about to be reset, so ignore errors.
-         * Not supported on P9 DD1
          */
-        if ((cxl_is_power8()) || (!(cxl_is_power9_dd1())))
-                cxl_data_cache_flush(adapter);
+        cxl_data_cache_flush(adapter);
 
         /* pcie_warm_reset requests a fundamental pci reset which includes a
          * PERST assert/deassert.  PERST triggers a loading of the image
@@ -1934,10 +1943,8 @@ static void cxl_pci_remove_adapter(struct cxl *adapter)
 
         /*
          * Flush adapter datacache as its about to be removed.
-         * Not supported on P9 DD1.
          */
-        if ((cxl_is_power8()) || (!(cxl_is_power9_dd1())))
-                cxl_data_cache_flush(adapter);
+        cxl_data_cache_flush(adapter);
 
         cxl_deconfigure_adapter(adapter);