[PATCH 2/4] mpt3sas: Add separate function for aero doorbell reads.

[Suganath Prabu <suganath-prabu.subramani@xxxxxxxxxxxx>]

Sometimes Aero controllers appears to be returning bad data (0)
for doorbell register read and if retries are performed immediately
after the bad read, they return good data.

Workaround is added to retry read from doorbell registers
for maximum three times if driver get the zero.
Added functions base_readl_aero for Aero IOC and base_readl for
gen35 and other controllers.

Signed-off-by: Suganath Prabu <suganath-prabu.subramani@xxxxxxxxxxxx>
---
 drivers/scsi/mpt3sas/mpt3sas_base.c | 30 ++++++++++++++++++++++++++++++
 drivers/scsi/mpt3sas/mpt3sas_base.h |  2 ++
 2 files changed, 32 insertions(+)

diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
index 9254b52..d371c8e 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.c
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
@@ -157,6 +157,32 @@ module_param_call(mpt3sas_fwfault_debug, _scsih_set_fwfault_debug,
 	param_get_int, &mpt3sas_fwfault_debug, 0644);
 
 /**
+ * _base_readl_aero - retry readl for max three times.
+ * @addr - MPT Fusion system interface register address
+ *
+ * Retry the readl() for max three times if it gets zero value
+ * while reading the system interface register.
+ */
+static inline u32
+_base_readl_aero(const volatile void __iomem *addr)
+{
+	u32 i = 0, ret_val;
+
+	do {
+		ret_val = readl(addr);
+		i++;
+	} while (ret_val == 0 && i < 3);
+
+	return ret_val;
+}
+
+static inline u32
+_base_readl(const volatile void __iomem *addr)
+{
+	return readl(addr);
+}
+
+/**
  * _base_clone_reply_to_sys_mem - copies reply to reply free iomem
  *				  in BAR0 space.
  *
@@ -6398,6 +6424,10 @@ mpt3sas_base_attach(struct MPT3SAS_ADAPTER *ioc)
 
 	ioc->rdpq_array_enable_assigned = 0;
 	ioc->dma_mask = 0;
+	if (ioc->is_aero_ioc)
+		ioc->base_readl = &_base_readl_aero;
+	else
+		ioc->base_readl = &_base_readl;
 	r = mpt3sas_base_map_resources(ioc);
 	if (r)
 		goto out_free_resources;
diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.h b/drivers/scsi/mpt3sas/mpt3sas_base.h
index f200929..3a294b9 100644
--- a/drivers/scsi/mpt3sas/mpt3sas_base.h
+++ b/drivers/scsi/mpt3sas/mpt3sas_base.h
@@ -912,6 +912,7 @@ typedef void (*NVME_BUILD_PRP)(struct MPT3SAS_ADAPTER *ioc, u16 smid,
 typedef void (*PUT_SMID_IO_FP_HIP) (struct MPT3SAS_ADAPTER *ioc, u16 smid,
 	u16 funcdep);
 typedef void (*PUT_SMID_DEFAULT) (struct MPT3SAS_ADAPTER *ioc, u16 smid);
+typedef u32 (*BASE_READ_REG) (const volatile void __iomem *addr);
 
 /* IOC Facts and Port Facts converted from little endian to cpu */
 union mpi3_version_union {
@@ -1392,6 +1393,7 @@ struct MPT3SAS_ADAPTER {
 	u8		hide_drives;
 	spinlock_t	diag_trigger_lock;
 	u8		diag_trigger_active;
+	BASE_READ_REG	base_readl;
 	struct SL_WH_MASTER_TRIGGER_T diag_trigger_master;
 	struct SL_WH_EVENT_TRIGGERS_T diag_trigger_event;
 	struct SL_WH_SCSI_TRIGGERS_T diag_trigger_scsi;
-- 
1.8.3.1