nvme-pci: allow use of cmb on v1.4 controllers

Since NVMe v1.4 the Controller Memory Buffer must be explicitly enabled
by the host.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
[hch: avoid a local variable and add a comment]
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/pci.c

@@ -23,6 +23,7 @@
 #include <linux/t10-pi.h>
 #include <linux/types.h>
 #include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/io-64-nonatomic-hi-lo.h>
 #include <linux/sed-opal.h>
 #include <linux/pci-p2pdma.h>
 
@@ -1795,6 +1796,9 @@ static void nvme_map_cmb(struct nvme_dev *dev)
 	if (dev->cmb_size)
 		return;
 
+	if (NVME_CAP_CMBS(dev->ctrl.cap))
+		writel(NVME_CMBMSC_CRE, dev->bar + NVME_REG_CMBMSC);
+
 	dev->cmbsz = readl(dev->bar + NVME_REG_CMBSZ);
 	if (!dev->cmbsz)
 		return;
@@ -1808,6 +1812,16 @@ static void nvme_map_cmb(struct nvme_dev *dev)
 	if (offset > bar_size)
 		return;
 
+	/*
+	 * Tell the controller about the host side address mapping the CMB,
+	 * and enable CMB decoding for the NVMe 1.4+ scheme:
+	 */
+	if (NVME_CAP_CMBS(dev->ctrl.cap)) {
+		hi_lo_writeq(NVME_CMBMSC_CRE | NVME_CMBMSC_CMSE |
+			     (pci_bus_address(pdev, bar) + offset),
+			     dev->bar + NVME_REG_CMBMSC);
+	}
+
 	/*
 	 * Controllers may support a CMB size larger than their BAR,
 	 * for example, due to being behind a bridge. Reduce the CMB to

include/linux/nvme.h

@@ -116,6 +116,9 @@ enum {
 	NVME_REG_BPMBL	= 0x0048,	/* Boot Partition Memory Buffer
 					 * Location
 					 */
+	NVME_REG_CMBMSC = 0x0050,	/* Controller Memory Buffer Memory
+					 * Space Control
+					 */
 	NVME_REG_PMRCAP	= 0x0e00,	/* Persistent Memory Capabilities */
 	NVME_REG_PMRCTL	= 0x0e04,	/* Persistent Memory Region Control */
 	NVME_REG_PMRSTS	= 0x0e08,	/* Persistent Memory Region Status */
@@ -135,6 +138,7 @@ enum {
 #define NVME_CAP_CSS(cap)	(((cap) >> 37) & 0xff)
 #define NVME_CAP_MPSMIN(cap)	(((cap) >> 48) & 0xf)
 #define NVME_CAP_MPSMAX(cap)	(((cap) >> 52) & 0xf)
+#define NVME_CAP_CMBS(cap)	(((cap) >> 57) & 0x1)
 
 #define NVME_CMB_BIR(cmbloc)	((cmbloc) & 0x7)
 #define NVME_CMB_OFST(cmbloc)	(((cmbloc) >> 12) & 0xfffff)
@@ -192,6 +196,8 @@ enum {
 	NVME_CSTS_SHST_OCCUR	= 1 << 2,
 	NVME_CSTS_SHST_CMPLT	= 2 << 2,
 	NVME_CSTS_SHST_MASK	= 3 << 2,
+	NVME_CMBMSC_CRE		= 1 << 0,
+	NVME_CMBMSC_CMSE	= 1 << 1,
 };
 
 struct nvme_id_power_state {