ufs: Add support for clock gating

The UFS controller clocks can be gated after certain period of
inactivity, which is typically less than runtime suspend timeout.
In addition to clocks the link will also be put into Hibern8 mode
to save more power.

The clock gating can be turned on by enabling the capability
UFSHCD_CAP_CLK_GATING. To enable entering into Hibern8 mode as part of
clock gating, set the capability UFSHCD_CAP_HIBERN8_WITH_CLK_GATING.

The tracing events for clock gating can be enabled through debugfs as:
echo 1 > /sys/kernel/debug/tracing/events/ufs/ufshcd_clk_gating/enable
cat /sys/kernel/debug/tracing/trace_pipe
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Dolev Raviv <draviv@codeaurora.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/ufs/ufshcd.h

@@ -269,6 +269,38 @@ struct ufs_hba_variant_ops {
 	int     (*resume)(struct ufs_hba *, enum ufs_pm_op);
 };
 
+/* clock gating state  */
+enum clk_gating_state {
+	CLKS_OFF,
+	CLKS_ON,
+	REQ_CLKS_OFF,
+	REQ_CLKS_ON,
+};
+
+/**
+ * struct ufs_clk_gating - UFS clock gating related info
+ * @gate_work: worker to turn off clocks after some delay as specified in
+ * delay_ms
+ * @ungate_work: worker to turn on clocks that will be used in case of
+ * interrupt context
+ * @state: the current clocks state
+ * @delay_ms: gating delay in ms
+ * @is_suspended: clk gating is suspended when set to 1 which can be used
+ * during suspend/resume
+ * @delay_attr: sysfs attribute to control delay_attr
+ * @active_reqs: number of requests that are pending and should be waited for
+ * completion before gating clocks.
+ */
+struct ufs_clk_gating {
+	struct delayed_work gate_work;
+	struct work_struct ungate_work;
+	enum clk_gating_state state;
+	unsigned long delay_ms;
+	bool is_suspended;
+	struct device_attribute delay_attr;
+	int active_reqs;
+};
+
 /**
  * struct ufs_init_prefetch - contains data that is pre-fetched once during
  * initialization
@@ -414,8 +446,25 @@ struct ufs_hba {
 
 	struct ufs_pa_layer_attr pwr_info;
 	struct ufs_pwr_mode_info max_pwr_info;
+
+	struct ufs_clk_gating clk_gating;
+	/* Control to enable/disable host capabilities */
+	u32 caps;
+	/* Allow dynamic clk gating */
+#define UFSHCD_CAP_CLK_GATING	(1 << 0)
+	/* Allow hiberb8 with clk gating */
+#define UFSHCD_CAP_HIBERN8_WITH_CLK_GATING (1 << 1)
 };
 
+/* Returns true if clocks can be gated. Otherwise false */
+static inline bool ufshcd_is_clkgating_allowed(struct ufs_hba *hba)
+{
+	return hba->caps & UFSHCD_CAP_CLK_GATING;
+}
+static inline bool ufshcd_can_hibern8_during_gating(struct ufs_hba *hba)
+{
+	return hba->caps & UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
+}
 #define ufshcd_writel(hba, val, reg)	\
 	writel((val), (hba)->mmio_base + (reg))
 #define ufshcd_readl(hba, reg)	\
@@ -497,4 +546,6 @@ static inline int ufshcd_dme_peer_get(struct ufs_hba *hba,
 	return ufshcd_dme_get_attr(hba, attr_sel, mib_val, DME_PEER);
 }
 
+int ufshcd_hold(struct ufs_hba *hba, bool async);
+void ufshcd_release(struct ufs_hba *hba);
 #endif /* End of Header */