[PATCH 4.16 179/272] cxl: Check if PSL data-cache is available before issue flush request

Greg Kroah-Hartman
2018-05-28T11:12:23Z

From: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>

[ Upstream commit 94322ed8e857e3b2a33cf75118051af9baaa110f ]

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>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/misc/cxl/cxl.h | 4 ++++
drivers/misc/cxl/native.c | 11 ++++++++++-
drivers/misc/cxl/pci.c | 19 +++++++++++++------
3 files changed, 27 insertions(+), 7 deletions(-)

--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -369,6 +369,9 @@ static const cxl_p2n_reg_t CXL_PSL_WED_A
#define CXL_PSL_TFC_An_AE (1ull << (63-30)) /* Restart PSL with address error */
#define CXL_PSL_TFC_An_R (1ull << (63-31)) /* Restart PSL transaction */

+/****** CXL_PSL_DEBUG *****************************************************/
+#define CXL_PSL_DEBUG_CDC (1ull << (63-27)) /* Coherent Data cache support */
+
/****** CXL_XSL9_IERAT_ERAT - CAIA 2 **********************************/
#define CXL_XSL9_IERAT_MLPID (1ull << (63-0)) /* Match LPID */
#define CXL_XSL9_IERAT_MPID (1ull << (63-1)) /* Match PID */
@@ -669,6 +672,7 @@ struct cxl_native {
irq_hw_number_t err_hwirq;
unsigned int err_virq;
u64 ps_off;
+ bool no_data_cache; /* set if no data cache on the card */
const struct cxl_service_layer_ops *sl_ops;
};

--- a/drivers/misc/cxl/native.c
+++ b/drivers/misc/cxl/native.c
@@ -353,8 +353,17 @@ int cxl_data_cache_flush(struct cxl *ada
u64 reg;
unsigned long timeout = jiffies + (HZ * CXL_TIMEOUT);

- pr_devel("Flushing data cache\n");
+ /*
+ * Do a datacache flush only if datacache is available.
+ * In case of PSL9D datacache absent hence flush operation.
+ * would timeout.
+ */
+ if (adapter->native->no_data_cache) {
+ pr_devel("No PSL data cache. Ignoring cache flush req.\n");
+ return 0;
+ }

+ pr_devel("Flushing data cache\n");
reg = cxl_p1_read(adapter, CXL_PSL_Control);
reg |= CXL_PSL_Control_Fr;
cxl_p1_write(adapter, CXL_PSL_Control, reg);
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -456,6 +456,7 @@ static int init_implementation_adapter_r
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);
@@ -506,6 +507,16 @@ static int init_implementation_adapter_r
} else
cxl_p1_write(adapter, CXL_PSL9_DEBUG, 0x4000000000000000ULL);

+ /*
+ * 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;
}

@@ -1449,10 +1460,8 @@ 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
@@ -1936,10 +1945,8 @@ static void cxl_pci_remove_adapter(struc

/*
* 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);