pmdomain: mediatek: Add support for Hardware Voter power domains

New generation SoCs like MT8196/MT6991 feature a new type of power
domains, managed by a Hardware Voter (HWV) helper (through a SoC
internal fixed-function MCU): this is used to collect votes from
both the AP and the various other remote processors present in the
SoC and transparently power on/off various power domains, avoiding
unpowered access of registers in various internal IPs from all of
the integrated remote processors (or from the AP...!).

Add a new power domain type and differentiate between the old
SCPSYS_MTCMOS_TYPE_DIRECT_CTL - where power domains are controlled
directly by and exclusively from the Application Processor, and
the new SCPSYS_MTCMOS_TYPE_HW_VOTER, where the power domains are
voted through the HWV.

With the two needing different handling, check the power domain
type and assign a different power_{off,on} callback for pm_genpd:
for this specific reason, also move the check for the SCPD cap
MTK_SCPD_KEEP_DEFAULT_OFF after the assignment, and use the
assigned power_on function instead of calling scpsys_power_on()
directly to make that work for both HW_VOTER and DIRECT_CTL.

Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Author: AngeloGioacchino Del Regno

drivers/pmdomain/mediatek/mtk-pm-domains.c

@@ -31,6 +31,12 @@
 #define MTK_POLL_DELAY_US		10
 #define MTK_POLL_TIMEOUT		USEC_PER_SEC
 
+#define MTK_HWV_POLL_DELAY_US		5
+#define MTK_HWV_POLL_TIMEOUT		(300 * USEC_PER_MSEC)
+
+#define MTK_HWV_PREPARE_DELAY_US	1
+#define MTK_HWV_PREPARE_TIMEOUT		(3 * USEC_PER_MSEC)
+
 #define PWR_RST_B_BIT			BIT(0)
 #define PWR_ISO_BIT			BIT(1)
 #define PWR_ON_BIT			BIT(2)
@@ -48,6 +54,7 @@
 struct scpsys_domain {
 	struct generic_pm_domain genpd;
 	const struct scpsys_domain_data *data;
+	const struct scpsys_hwv_domain_data *hwv_data;
 	struct scpsys *scpsys;
 	int num_clks;
 	struct clk_bulk_data *clks;
@@ -83,6 +90,32 @@ static bool scpsys_domain_is_on(struct scpsys_domain *pd)
 	return status && status2;
 }
 
+static bool scpsys_hwv_domain_is_disable_done(struct scpsys_domain *pd)
+{
+	const struct scpsys_hwv_domain_data *hwv = pd->hwv_data;
+	u32 regs[2] = { hwv->done, hwv->clr_sta };
+	u32 val[2];
+	u32 mask = BIT(hwv->setclr_bit);
+
+	regmap_multi_reg_read(pd->scpsys->base, regs, val, 2);
+
+	/* Disable is done when the bit is set in DONE, cleared in CLR_STA */
+	return (val[0] & mask) && !(val[1] & mask);
+}
+
+static bool scpsys_hwv_domain_is_enable_done(struct scpsys_domain *pd)
+{
+	const struct scpsys_hwv_domain_data *hwv = pd->hwv_data;
+	u32 regs[3] = { hwv->done, hwv->en, hwv->set_sta };
+	u32 val[3];
+	u32 mask = BIT(hwv->setclr_bit);
+
+	regmap_multi_reg_read(pd->scpsys->base, regs, val, 3);
+
+	/* Enable is done when the bit is set in DONE and EN, cleared in SET_STA */
+	return (val[0] & mask) && (val[1] & mask) && !(val[2] & mask);
+}
+
 static int scpsys_sram_enable(struct scpsys_domain *pd)
 {
 	u32 expected_ack, pdn_ack = pd->data->sram_pdn_ack_bits;
@@ -250,6 +283,137 @@ static int scpsys_regulator_disable(struct regulator *supply)
 	return supply ? regulator_disable(supply) : 0;
 }
 
+static int scpsys_hwv_power_on(struct generic_pm_domain *genpd)
+{
+	struct scpsys_domain *pd = container_of(genpd, struct scpsys_domain, genpd);
+	const struct scpsys_hwv_domain_data *hwv = pd->hwv_data;
+	struct scpsys *scpsys = pd->scpsys;
+	u32 val;
+	int ret;
+
+	ret = scpsys_regulator_enable(pd->supply);
+	if (ret)
+		return ret;
+
+	ret = clk_bulk_prepare_enable(pd->num_clks, pd->clks);
+	if (ret)
+		goto err_reg;
+
+	/* For HWV the subsys clocks refer to the HWV low power subsystem */
+	ret = clk_bulk_prepare_enable(pd->num_subsys_clks, pd->subsys_clks);
+	if (ret)
+		goto err_disable_clks;
+
+	/* Make sure the HW Voter is idle and able to accept commands */
+	ret = regmap_read_poll_timeout_atomic(scpsys->base, hwv->done, val,
+					      val & BIT(hwv->setclr_bit),
+					      MTK_HWV_POLL_DELAY_US,
+					      MTK_HWV_POLL_TIMEOUT);
+	if (ret) {
+		dev_err(scpsys->dev, "Failed to power on: HW Voter busy.\n");
+		goto err_disable_subsys_clks;
+	}
+
+	/*
+	 * Instruct the HWV to power on the MTCMOS (power domain): after that,
+	 * the same bit will be unset immediately by the hardware.
+	 */
+	regmap_write(scpsys->base, hwv->set, BIT(hwv->setclr_bit));
+
+	/*
+	 * Wait until the HWV sets the bit again, signalling that its internal
+	 * state machine was started and it now processing the vote command.
+	 */
+	ret = regmap_read_poll_timeout_atomic(scpsys->base, hwv->set, val,
+					      val & BIT(hwv->setclr_bit),
+					      MTK_HWV_PREPARE_DELAY_US,
+					      MTK_HWV_PREPARE_TIMEOUT);
+	if (ret) {
+		dev_err(scpsys->dev, "Failed to power on: HW Voter not starting.\n");
+		goto err_disable_subsys_clks;
+	}
+
+	/* Wait for ACK, signalling that the MTCMOS was enabled */
+	ret = readx_poll_timeout_atomic(scpsys_hwv_domain_is_enable_done, pd, val, val,
+					MTK_HWV_POLL_DELAY_US, MTK_HWV_POLL_TIMEOUT);
+	if (ret) {
+		dev_err(scpsys->dev, "Failed to power on: HW Voter ACK timeout.\n");
+		goto err_disable_subsys_clks;
+	}
+
+	/* It's done! Disable the HWV low power subsystem clocks */
+	clk_bulk_disable_unprepare(pd->num_subsys_clks, pd->subsys_clks);
+
+	return 0;
+
+err_disable_subsys_clks:
+	clk_bulk_disable_unprepare(pd->num_subsys_clks, pd->subsys_clks);
+err_disable_clks:
+	clk_bulk_disable_unprepare(pd->num_clks, pd->clks);
+err_reg:
+	scpsys_regulator_disable(pd->supply);
+	return ret;
+};
+
+static int scpsys_hwv_power_off(struct generic_pm_domain *genpd)
+{
+	struct scpsys_domain *pd = container_of(genpd, struct scpsys_domain, genpd);
+	const struct scpsys_hwv_domain_data *hwv = pd->hwv_data;
+	struct scpsys *scpsys = pd->scpsys;
+	u32 val;
+	int ret;
+
+	ret = clk_bulk_prepare_enable(pd->num_subsys_clks, pd->subsys_clks);
+	if (ret)
+		return ret;
+
+	/* Make sure the HW Voter is idle and able to accept commands */
+	ret = regmap_read_poll_timeout_atomic(scpsys->base, hwv->done, val,
+					      val & BIT(hwv->setclr_bit),
+					      MTK_HWV_POLL_DELAY_US,
+					      MTK_HWV_POLL_TIMEOUT);
+	if (ret)
+		goto err_disable_subsys_clks;
+
+
+	/*
+	 * Instruct the HWV to power off the MTCMOS (power domain): differently
+	 * from poweron, the bit will be kept set.
+	 */
+	regmap_write(scpsys->base, hwv->clr, BIT(hwv->setclr_bit));
+
+	/*
+	 * Wait until the HWV clears the bit, signalling that its internal
+	 * state machine was started and it now processing the clear command.
+	 */
+	ret = regmap_read_poll_timeout_atomic(scpsys->base, hwv->clr, val,
+					      !(val & BIT(hwv->setclr_bit)),
+					      MTK_HWV_PREPARE_DELAY_US,
+					      MTK_HWV_PREPARE_TIMEOUT);
+	if (ret)
+		goto err_disable_subsys_clks;
+
+	/* Poweroff needs 100us for the HW to stabilize */
+	udelay(100);
+
+	/* Wait for ACK, signalling that the MTCMOS was disabled */
+	ret = readx_poll_timeout_atomic(scpsys_hwv_domain_is_disable_done, pd, val, val,
+					MTK_HWV_POLL_DELAY_US, MTK_HWV_POLL_TIMEOUT);
+	if (ret)
+		goto err_disable_subsys_clks;
+
+	clk_bulk_disable_unprepare(pd->num_subsys_clks, pd->subsys_clks);
+	clk_bulk_disable_unprepare(pd->num_clks, pd->clks);
+
+	scpsys_regulator_disable(pd->supply);
+
+	return 0;
+
+err_disable_subsys_clks:
+	clk_bulk_disable_unprepare(pd->num_subsys_clks, pd->subsys_clks);
+	return ret;
+};
+
 static int scpsys_ctl_pwrseq_on(struct scpsys_domain *pd)
 {
 	struct scpsys *scpsys = pd->scpsys;
@@ -514,6 +678,7 @@ static struct
 generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_node *node)
 {
 	const struct scpsys_domain_data *domain_data;
+	const struct scpsys_hwv_domain_data *hwv_domain_data;
 	struct scpsys_domain *pd;
 	struct property *prop;
 	const char *clk_name;
@@ -529,14 +694,33 @@ generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_no
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (id >= scpsys->soc_data->num_domains) {
-		dev_err(scpsys->dev, "%pOF: invalid domain id %d\n", node, id);
-		return ERR_PTR(-EINVAL);
-	}
+	switch (scpsys->soc_data->type) {
+	case SCPSYS_MTCMOS_TYPE_DIRECT_CTL:
+		if (id >= scpsys->soc_data->num_domains) {
+			dev_err(scpsys->dev, "%pOF: invalid domain id %d\n", node, id);
+			return ERR_PTR(-EINVAL);
+		}
+
+		domain_data = &scpsys->soc_data->domains_data[id];
+		hwv_domain_data = NULL;
 
-	domain_data = &scpsys->soc_data->domains_data[id];
-	if (domain_data->sta_mask == 0) {
-		dev_err(scpsys->dev, "%pOF: undefined domain id %d\n", node, id);
+		if (domain_data->sta_mask == 0) {
+			dev_err(scpsys->dev, "%pOF: undefined domain id %d\n", node, id);
+			return ERR_PTR(-EINVAL);
+		}
+
+		break;
+	case SCPSYS_MTCMOS_TYPE_HW_VOTER:
+		if (id >= scpsys->soc_data->num_hwv_domains) {
+			dev_err(scpsys->dev, "%pOF: invalid HWV domain id %d\n", node, id);
+			return ERR_PTR(-EINVAL);
+		}
+
+		domain_data = NULL;
+		hwv_domain_data = &scpsys->soc_data->hwv_domains_data[id];
+
+		break;
+	default:
 		return ERR_PTR(-EINVAL);
 	}
 
@@ -545,6 +729,7 @@ generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_no
 		return ERR_PTR(-ENOMEM);
 
 	pd->data = domain_data;
+	pd->hwv_data = hwv_domain_data;
 	pd->scpsys = scpsys;
 
 	if (MTK_SCPD_CAPS(pd, MTK_SCPD_DOMAIN_SUPPLY)) {
@@ -604,6 +789,31 @@ generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_no
 		pd->subsys_clks[i].clk = clk;
 	}
 
+	if (scpsys->domains[id]) {
+		ret = -EINVAL;
+		dev_err(scpsys->dev,
+			"power domain with id %d already exists, check your device-tree\n", id);
+		goto err_put_subsys_clocks;
+	}
+
+	if (pd->data && pd->data->name)
+		pd->genpd.name = pd->data->name;
+	else if (pd->hwv_data && pd->hwv_data->name)
+		pd->genpd.name = pd->hwv_data->name;
+	else
+		pd->genpd.name = node->name;
+
+	if (scpsys->soc_data->type == SCPSYS_MTCMOS_TYPE_DIRECT_CTL) {
+		pd->genpd.power_off = scpsys_power_off;
+		pd->genpd.power_on = scpsys_power_on;
+	} else {
+		pd->genpd.power_off = scpsys_hwv_power_off;
+		pd->genpd.power_on = scpsys_hwv_power_on;
+
+		/* HW-Voter code can be invoked in atomic context */
+		pd->genpd.flags |= GENPD_FLAG_IRQ_SAFE;
+	}
+
 	/*
 	 * Initially turn on all domains to make the domains usable
 	 * with !CONFIG_PM and to get the hardware in sync with the
@@ -615,7 +825,7 @@ generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_no
 			dev_warn(scpsys->dev,
 				 "%pOF: A default off power domain has been ON\n", node);
 	} else {
-		ret = scpsys_power_on(&pd->genpd);
+		ret = pd->genpd.power_on(&pd->genpd);
 		if (ret < 0) {
 			dev_err(scpsys->dev, "%pOF: failed to power on domain: %d\n", node, ret);
 			goto err_put_subsys_clocks;
@@ -625,21 +835,6 @@ generic_pm_domain *scpsys_add_one_domain(struct scpsys *scpsys, struct device_no
 			pd->genpd.flags |= GENPD_FLAG_ALWAYS_ON;
 	}
 
-	if (scpsys->domains[id]) {
-		ret = -EINVAL;
-		dev_err(scpsys->dev,
-			"power domain with id %d already exists, check your device-tree\n", id);
-		goto err_put_subsys_clocks;
-	}
-
-	if (!pd->data->name)
-		pd->genpd.name = node->name;
-	else
-		pd->genpd.name = pd->data->name;
-
-	pd->genpd.power_off = scpsys_power_off;
-	pd->genpd.power_on = scpsys_power_on;
-
 	if (MTK_SCPD_CAPS(pd, MTK_SCPD_ACTIVE_WAKEUP))
 		pd->genpd.flags |= GENPD_FLAG_ACTIVE_WAKEUP;
 
@@ -934,15 +1129,17 @@ static int scpsys_probe(struct platform_device *pdev)
 	struct device_node *node;
 	struct device *parent;
 	struct scpsys *scpsys;
-	int ret;
+	int num_domains, ret;
 
 	soc = of_device_get_match_data(&pdev->dev);
 	if (!soc) {
 		dev_err(&pdev->dev, "no power controller data\n");
 		return -EINVAL;
 	}
 
-	scpsys = devm_kzalloc(dev, struct_size(scpsys, domains, soc->num_domains), GFP_KERNEL);
+	num_domains = soc->num_domains + soc->num_hwv_domains;
+
+	scpsys = devm_kzalloc(dev, struct_size(scpsys, domains, num_domains), GFP_KERNEL);
 	if (!scpsys)
 		return -ENOMEM;