scsi: ufs: ufs-mediatek: Support clk-scaling to optimize power consumption

Provide clk-scaling feature in MediaTek UFS platforms.

MediaTek platform supports clk-scaling by switching parent clock mux of
UFSHCI main clocks: ufs_sel.

The driver needs to prevent changing the rate of ufs_sel because its parent
PLL clock may be shared between multiple IPs. In order to achieve this
goal, the maximum and minimum clock rates of ufs_sel defined in dts should
match the rate of "ufs_sel_max_src" and "ufs_sel_min_src" respectively.

Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Stanley Chu <[e-mail]>
Signed-off-by: Po-Wen Kao <[e-mail]>
Signed-off-by: Stanley Chu <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/ufs/host/ufs-mediatek-trace.h

···
 		__entry->data = data;
 	),
 
-	TP_printk("ufs:event=%u data=%u",
+	TP_printk("ufs: event=%u data=%u",
 		  __entry->type, __entry->data)
-	);
+);
+
+TRACE_EVENT(ufs_mtk_clk_scale,
+	TP_PROTO(const char *name, bool scale_up, unsigned long clk_rate),
+	TP_ARGS(name, scale_up, clk_rate),
+
+	TP_STRUCT__entry(
+		__field(const char*, name)
+		__field(bool, scale_up)
+		__field(unsigned long, clk_rate)
+	),
+
+	TP_fast_assign(
+		__entry->name = name;
+		__entry->scale_up = scale_up;
+		__entry->clk_rate = clk_rate;
+	),
+
+	TP_printk("ufs: clk (%s) scaled %s @ %lu",
+		  __entry->name,
+		  __entry->scale_up ? "up" : "down",
+		  __entry->clk_rate)
+);
+
 #endif
 
 #undef TRACE_INCLUDE_PATH

drivers/ufs/host/ufs-mediatek.c

···
 	return hba->ufs_version;
 }
 
+/**
+ * ufs_mtk_init_clocks - Init mtk driver private clocks
+ *
+ * @hba: per adapter instance
+ */
+static void ufs_mtk_init_clocks(struct ufs_hba *hba)
+{
+	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
+	struct list_head *head = &hba->clk_list_head;
+	struct ufs_mtk_clk *mclk = &host->mclk;
+	struct ufs_clk_info *clki, *clki_tmp;
+
+	/*
+	 * Find private clocks and store them in struct ufs_mtk_clk.
+	 * Remove "ufs_sel_min_src" and "ufs_sel_min_src" from list to avoid
+	 * being switched on/off in clock gating.
+	 */
+	list_for_each_entry_safe(clki, clki_tmp, head, list) {
+		if (!strcmp(clki->name, "ufs_sel")) {
+			host->mclk.ufs_sel_clki = clki;
+		} else if (!strcmp(clki->name, "ufs_sel_max_src")) {
+			host->mclk.ufs_sel_max_clki = clki;
+			clk_disable_unprepare(clki->clk);
+			list_del(&clki->list);
+		} else if (!strcmp(clki->name, "ufs_sel_min_src")) {
+			host->mclk.ufs_sel_min_clki = clki;
+			clk_disable_unprepare(clki->clk);
+			list_del(&clki->list);
+		}
+	}
+
+	if (!mclk->ufs_sel_clki || !mclk->ufs_sel_max_clki ||
+	    !mclk->ufs_sel_min_clki) {
+		hba->caps &= ~UFSHCD_CAP_CLK_SCALING;
+		dev_info(hba->dev,
+			 "%s: Clk-scaling not ready. Feature disabled.",
+			 __func__);
+	}
+}
+
 #define MAX_VCC_NAME 30
 static int ufs_mtk_vreg_fix_vcc(struct ufs_hba *hba)
 {
···
 
 	/* Enable WriteBooster */
 	hba->caps |= UFSHCD_CAP_WB_EN;
+
+	/* Enable clk scaling*/
+	hba->caps |= UFSHCD_CAP_CLK_SCALING;
+
 	hba->quirks |= UFSHCI_QUIRK_SKIP_MANUAL_WB_FLUSH_CTRL;
 	hba->vps->wb_flush_threshold = UFS_WB_BUF_REMAIN_PERCENT(80);
 
 	if (host->caps & UFS_MTK_CAP_DISABLE_AH8)
 		hba->caps |= UFSHCD_CAP_HIBERN8_WITH_CLK_GATING;
+
+	ufs_mtk_init_clocks(hba);
 
 	/*
 	 * ufshcd_vops_init() is invoked after
···
 	}
 }
 
+static void ufs_mtk_config_scaling_param(struct ufs_hba *hba,
+				struct devfreq_dev_profile *profile,
+				struct devfreq_simple_ondemand_data *data)
+{
+	/* Customize min gear in clk scaling */
+	hba->clk_scaling.min_gear = UFS_HS_G4;
+
+	hba->vps->devfreq_profile.polling_ms = 200;
+	hba->vps->ondemand_data.upthreshold = 50;
+	hba->vps->ondemand_data.downdifferential = 20;
+}
+
+/**
+ * ufs_mtk_clk_scale - Internal clk scaling operation
+ *
+ * MTK platform supports clk scaling by switching parent of ufs_sel(mux).
+ * The ufs_sel downstream to ufs_ck which feeds directly to UFS hardware.
+ * Max and min clocks rate of ufs_sel defined in dts should match rate of
+ * "ufs_sel_max_src" and "ufs_sel_min_src" respectively.
+ * This prevent changing rate of pll clock that is shared between modules.
+ *
+ * @hba: per adapter instance
+ * @scale_up: True for scaling up and false for scaling down
+ */
+static void ufs_mtk_clk_scale(struct ufs_hba *hba, bool scale_up)
+{
+	struct ufs_mtk_host *host = ufshcd_get_variant(hba);
+	struct ufs_mtk_clk *mclk = &host->mclk;
+	struct ufs_clk_info *clki = mclk->ufs_sel_clki;
+	int ret = 0;
+
+	ret = clk_prepare_enable(clki->clk);
+	if (ret) {
+		dev_info(hba->dev,
+			 "clk_prepare_enable() fail, ret: %d\n", ret);
+		return;
+	}
+
+	if (scale_up) {
+		ret = clk_set_parent(clki->clk, mclk->ufs_sel_max_clki->clk);
+		clki->curr_freq = clki->max_freq;
+	} else {
+		ret = clk_set_parent(clki->clk, mclk->ufs_sel_min_clki->clk);
+		clki->curr_freq = clki->min_freq;
+	}
+
+	if (ret) {
+		dev_info(hba->dev,
+			 "Failed to set ufs_sel_clki, ret: %d\n", ret);
+	}
+
+	clk_disable_unprepare(clki->clk);
+
+	trace_ufs_mtk_clk_scale(clki->name, scale_up, clk_get_rate(clki->clk));
+}
+
+static int ufs_mtk_clk_scale_notify(struct ufs_hba *hba, bool scale_up,
+				    enum ufs_notify_change_status status)
+{
+	if (!ufshcd_is_clkscaling_supported(hba))
+		return 0;
+
+	if (status == PRE_CHANGE) {
+		/* Switch parent before clk_set_rate() */
+		ufs_mtk_clk_scale(hba, scale_up);
+	} else {
+		/* Request interrupt latency QoS accordingly */
+		ufs_mtk_scale_perf(hba, scale_up);
+	}
+
+	return 0;
+}
+
 /*
  * struct ufs_hba_mtk_vops - UFS MTK specific variant operations
  *
···
 	.dbg_register_dump   = ufs_mtk_dbg_register_dump,
 	.device_reset        = ufs_mtk_device_reset,
 	.event_notify        = ufs_mtk_event_notify,
+	.config_scaling_param = ufs_mtk_config_scaling_param,
+	.clk_scale_notify    = ufs_mtk_clk_scale_notify,
 };
 
 /**

drivers/ufs/host/ufs-mediatek.h

···
 	int vcore_volt;
 };
 
+struct ufs_mtk_clk {
+	struct ufs_clk_info *ufs_sel_clki; /* Mux */
+	struct ufs_clk_info *ufs_sel_max_clki; /* Max src */
+	struct ufs_clk_info *ufs_sel_min_clki; /* Min src */
+};
+
 struct ufs_mtk_hw_ver {
 	u8 step;
 	u8 minor;
···
 	struct reset_control *crypto_reset;
 	struct ufs_hba *hba;
 	struct ufs_mtk_crypt_cfg *crypt;
+	struct ufs_mtk_clk mclk;
 	struct ufs_mtk_hw_ver hw_ver;
 	enum ufs_mtk_host_caps caps;
 	bool mphy_powered_on;