[PATCH] NVMe: Add nvme subsystem reset support

[Keith Busch]

Controllers part of an NVMe subsystem may be reset by any other controller
in the subsystem. If the device is capable of subsystem resets, this
patch adds detection for such events and performs appropriate controller
initialization upon subsystem reset detection. The register bit is a
type RW1C, so the driver needs to write a 1 to the status bit to clear
the subsystem reset occured bit during initialization.

Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/block/nvme-core.c |   11 ++++++++++-
 include/linux/nvme.h      |    3 +++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
index 62a147d..e3ebd27 100644
--- a/drivers/block/nvme-core.c
+++ b/drivers/block/nvme-core.c
@@ -1625,6 +1625,12 @@ static int nvme_configure_admin_queue(struct nvme_dev *dev)
 		page_shift = dev_page_max;
 	}
 
+	dev->subsystem = readl(&dev->bar->vs) >= NVME_VS(1, 1) ?
+						NVME_CAP_NSSRC(cap) : 0;
+
+	if (dev->subsystem && (readl(&dev->bar->csts) & NVME_CSTS_NSSRO))
+		writel(NVME_CSTS_NSSRO, &dev->bar->csts);
+
 	result = nvme_disable_ctrl(dev, cap);
 	if (result < 0)
 		return result;
@@ -2068,7 +2074,10 @@ static int nvme_kthread(void *data)
 		spin_lock(&dev_list_lock);
 		list_for_each_entry_safe(dev, next, &dev_list, node) {
 			int i;
-			if (readl(&dev->bar->csts) & NVME_CSTS_CFS) {
+			u32 csts = readl(&dev->bar->csts);
+
+			if ((dev->subsystem && (csts & NVME_CSTS_NSSRO)) ||
+							csts & NVME_CSTS_CFS) {
 				if (work_busy(&dev->reset_work))
 					continue;
 				list_del_init(&dev->node);
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 409d191..1f196b8 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -37,6 +37,7 @@ struct nvme_bar {
 #define NVME_CAP_MQES(cap)	((cap) & 0xffff)
 #define NVME_CAP_TIMEOUT(cap)	(((cap) >> 24) & 0xff)
 #define NVME_CAP_STRIDE(cap)	(((cap) >> 32) & 0xf)
+#define NVME_CAP_NSSRC(cap)	(((cap) >> 36) & 0x1)
 #define NVME_CAP_MPSMIN(cap)	(((cap) >> 48) & 0xf)
 #define NVME_CAP_MPSMAX(cap)	(((cap) >> 52) & 0xf)
 
@@ -55,6 +56,7 @@ enum {
 	NVME_CC_IOCQES		= 4 << 20,
 	NVME_CSTS_RDY		= 1 << 0,
 	NVME_CSTS_CFS		= 1 << 1,
+	NVME_CSTS_NSSRO		= 1 << 4,
 	NVME_CSTS_SHST_NORMAL	= 0 << 2,
 	NVME_CSTS_SHST_OCCUR	= 1 << 2,
 	NVME_CSTS_SHST_CMPLT	= 2 << 2,
@@ -98,6 +100,7 @@ struct nvme_dev {
 	char serial[20];
 	char model[40];
 	char firmware_rev[8];
+	bool subsystem;
 	u32 max_hw_sectors;
 	u32 stripe_size;
 	u32 page_size;
-- 
1.7.10.4