ipmi: kcs_bmc: Allow clients to control KCS IRQ state

Add a mechanism for controlling whether the client associated with a
KCS device will receive Input Buffer Full (IBF) and Output Buffer Empty
(OBE) events. This enables an abstract implementation of poll() for KCS
devices.

A wart in the implementation is that the ASPEED KCS devices don't
support an OBE interrupt for the BMC. Instead we pretend it has one by
polling the status register waiting for the Output Buffer Full (OBF) bit
to clear, and generating an event when OBE is observed.

Cc: CS20 KWLiu <KWLIU@nuvoton.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Zev Weiss <zweiss@equinix.com>
Message-Id: <20210608104757.582199-10-andrew@aj.id.au>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/kcs_bmc.c

@@ -182,6 +182,12 @@ void kcs_bmc_unregister_driver(struct kcs_bmc_driver *drv)
 }
 EXPORT_SYMBOL(kcs_bmc_unregister_driver);
 
+void kcs_bmc_update_event_mask(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 events)
+{
+	kcs_bmc->ops->irq_mask_update(kcs_bmc, mask, events);
+}
+EXPORT_SYMBOL(kcs_bmc_update_event_mask);
+
 MODULE_LICENSE("GPL v2");
 MODULE_AUTHOR("Haiyue Wang <haiyue.wang@linux.intel.com>");
 MODULE_AUTHOR("Andrew Jeffery <andrew@aj.id.au>");

drivers/char/ipmi/kcs_bmc.h

@@ -8,6 +8,9 @@
 
 #include <linux/list.h>
 
+#define KCS_BMC_EVENT_TYPE_OBE	BIT(0)
+#define KCS_BMC_EVENT_TYPE_IBF	BIT(1)
+
 #define KCS_BMC_STR_OBF		BIT(0)
 #define KCS_BMC_STR_IBF		BIT(1)
 #define KCS_BMC_STR_CMD_DAT	BIT(3)

drivers/char/ipmi/kcs_bmc_aspeed.c

@@ -60,10 +60,18 @@
 #define LPC_ODR4             0x118
 #define LPC_STR4             0x11C
 
+#define OBE_POLL_PERIOD	     (HZ / 2)
+
 struct aspeed_kcs_bmc {
 	struct kcs_bmc_device kcs_bmc;
 
 	struct regmap *map;
+
+	struct {
+		spinlock_t lock;
+		bool remove;
+		struct timer_list timer;
+	} obe;
 };
 
 struct aspeed_kcs_of_ops {
@@ -159,68 +167,89 @@ static void aspeed_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enabl
 
 	switch (kcs_bmc->channel) {
 	case 1:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF1, LPC_HICR2_IBFIF1);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC1E, LPC_HICR0_LPC1E);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC1E, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF1, 0);
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC1E, enable * LPC_HICR0_LPC1E);
+		return;
+	case 2:
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC2E, enable * LPC_HICR0_LPC2E);
+		return;
+	case 3:
+		regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC3E, enable * LPC_HICR0_LPC3E);
+		regmap_update_bits(priv->map, LPC_HICR4,
+				   LPC_HICR4_KCSENBL, enable * LPC_HICR4_KCSENBL);
+		return;
+	case 4:
+		regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_LPC4E, enable * LPC_HICRB_LPC4E);
+		return;
+	default:
+		pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+		return;
 	}
-		break;
+}
 
-	case 2:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF2, LPC_HICR2_IBFIF2);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC2E, LPC_HICR0_LPC2E);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC2E, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF2, 0);
+static void aspeed_kcs_check_obe(struct timer_list *timer)
+{
+	struct aspeed_kcs_bmc *priv = container_of(timer, struct aspeed_kcs_bmc, obe.timer);
+	unsigned long flags;
+	u8 str;
+
+	spin_lock_irqsave(&priv->obe.lock, flags);
+	if (priv->obe.remove) {
+		spin_unlock_irqrestore(&priv->obe.lock, flags);
+		return;
 	}
-		break;
 
-	case 3:
-		if (enable) {
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF3, LPC_HICR2_IBFIF3);
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC3E, LPC_HICR0_LPC3E);
-			regmap_update_bits(priv->map, LPC_HICR4,
-					LPC_HICR4_KCSENBL, LPC_HICR4_KCSENBL);
-		} else {
-			regmap_update_bits(priv->map, LPC_HICR0,
-					LPC_HICR0_LPC3E, 0);
-			regmap_update_bits(priv->map, LPC_HICR4,
-					LPC_HICR4_KCSENBL, 0);
-			regmap_update_bits(priv->map, LPC_HICR2,
-					LPC_HICR2_IBFIF3, 0);
+	str = aspeed_kcs_inb(&priv->kcs_bmc, priv->kcs_bmc.ioreg.str);
+	if (str & KCS_BMC_STR_OBF) {
+		mod_timer(timer, jiffies + OBE_POLL_PERIOD);
+		spin_unlock_irqrestore(&priv->obe.lock, flags);
+		return;
 	}
-		break;
+	spin_unlock_irqrestore(&priv->obe.lock, flags);
 
-	case 4:
-		if (enable)
-			regmap_update_bits(priv->map, LPC_HICRB,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E);
+	kcs_bmc_handle_event(&priv->kcs_bmc);
+}
+
+static void aspeed_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 state)
+{
+	struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
+
+	/* We don't have an OBE IRQ, emulate it */
+	if (mask & KCS_BMC_EVENT_TYPE_OBE) {
+		if (KCS_BMC_EVENT_TYPE_OBE & state)
+			mod_timer(&priv->obe.timer, jiffies + OBE_POLL_PERIOD);
 		else
-			regmap_update_bits(priv->map, LPC_HICRB,
-					LPC_HICRB_IBFIF4 | LPC_HICRB_LPC4E,
-					0);
-		break;
+			del_timer(&priv->obe.timer);
+	}
+
+	if (mask & KCS_BMC_EVENT_TYPE_IBF) {
+		const bool enable = !!(state & KCS_BMC_EVENT_TYPE_IBF);
 
+		switch (kcs_bmc->channel) {
+		case 1:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIF1,
+					   enable * LPC_HICR2_IBFIF1);
+			return;
+		case 2:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIF2,
+					   enable * LPC_HICR2_IBFIF2);
+			return;
+		case 3:
+			regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIF3,
+					   enable * LPC_HICR2_IBFIF3);
+			return;
+		case 4:
+			regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_IBFIF4,
+					   enable * LPC_HICRB_IBFIF4);
+			return;
 		default:
-		break;
+			pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+			return;
+		}
 	}
 }
 
 static const struct kcs_bmc_device_ops aspeed_kcs_ops = {
+	.irq_mask_update = aspeed_kcs_irq_mask_update,
 	.io_inputb = aspeed_kcs_inb,
 	.io_outputb = aspeed_kcs_outb,
 	.io_updateb = aspeed_kcs_updateb,
@@ -375,6 +404,10 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	spin_lock_init(&priv->obe.lock);
+	priv->obe.remove = false;
+	timer_setup(&priv->obe.timer, aspeed_kcs_check_obe, 0);
+
 	aspeed_kcs_set_address(kcs_bmc, addr);
 
 	rc = aspeed_kcs_config_irq(kcs_bmc, pdev);
@@ -383,6 +416,8 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, priv);
 
+	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
+				   KCS_BMC_EVENT_TYPE_IBF);
 	aspeed_kcs_enable_channel(kcs_bmc, true);
 
 	rc = kcs_bmc_add_device(&priv->kcs_bmc);
@@ -403,6 +438,15 @@ static int aspeed_kcs_remove(struct platform_device *pdev)
 
 	kcs_bmc_remove_device(kcs_bmc);
 
+	aspeed_kcs_enable_channel(kcs_bmc, false);
+	aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
+
+	/* Make sure it's proper dead */
+	spin_lock_irq(&priv->obe.lock);
+	priv->obe.remove = true;
+	spin_unlock_irq(&priv->obe.lock);
+	del_timer_sync(&priv->obe.timer);
+
 	return 0;
 }
 

drivers/char/ipmi/kcs_bmc_client.h

@@ -35,6 +35,8 @@ void kcs_bmc_unregister_driver(struct kcs_bmc_driver *drv);
 int kcs_bmc_enable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client);
 void kcs_bmc_disable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client);
 
+void kcs_bmc_update_event_mask(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 events);
+
 u8 kcs_bmc_read_data(struct kcs_bmc_device *kcs_bmc);
 void kcs_bmc_write_data(struct kcs_bmc_device *kcs_bmc, u8 data);
 u8 kcs_bmc_read_status(struct kcs_bmc_device *kcs_bmc);

drivers/char/ipmi/kcs_bmc_device.h

@@ -9,6 +9,7 @@
 #include "kcs_bmc.h"
 
 struct kcs_bmc_device_ops {
+	void (*irq_mask_update)(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 enable);
 	u8 (*io_inputb)(struct kcs_bmc_device *kcs_bmc, u32 reg);
 	void (*io_outputb)(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 b);
 	void (*io_updateb)(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 mask, u8 b);

drivers/char/ipmi/kcs_bmc_npcm7xx.c

@@ -38,6 +38,7 @@
 #define KCS2CTL		0x2A
 #define KCS3CTL		0x3C
 #define    KCS_CTL_IBFIE	BIT(0)
+#define    KCS_CTL_OBEIE	BIT(1)
 
 #define KCS1IE		0x1C
 #define KCS2IE		0x2E
@@ -117,13 +118,23 @@ static void npcm7xx_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enab
 {
 	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
 
-	regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_IBFIE,
-			   enable ? KCS_CTL_IBFIE : 0);
-
 	regmap_update_bits(priv->map, priv->reg->ie, KCS_IE_IRQE | KCS_IE_HIRQE,
 			   enable ? KCS_IE_IRQE | KCS_IE_HIRQE : 0);
 }
 
+static void npcm7xx_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask, u8 state)
+{
+	struct npcm7xx_kcs_bmc *priv = to_npcm7xx_kcs_bmc(kcs_bmc);
+
+	if (mask & KCS_BMC_EVENT_TYPE_OBE)
+		regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_OBEIE,
+				   !!(state & KCS_BMC_EVENT_TYPE_OBE) * KCS_CTL_OBEIE);
+
+	if (mask & KCS_BMC_EVENT_TYPE_IBF)
+		regmap_update_bits(priv->map, priv->reg->ctl, KCS_CTL_IBFIE,
+				   !!(state & KCS_BMC_EVENT_TYPE_IBF) * KCS_CTL_IBFIE);
+}
+
 static irqreturn_t npcm7xx_kcs_irq(int irq, void *arg)
 {
 	struct kcs_bmc_device *kcs_bmc = arg;
@@ -146,6 +157,7 @@ static int npcm7xx_kcs_config_irq(struct kcs_bmc_device *kcs_bmc,
 }
 
 static const struct kcs_bmc_device_ops npcm7xx_kcs_ops = {
+	.irq_mask_update = npcm7xx_kcs_irq_mask_update,
 	.io_inputb = npcm7xx_kcs_inb,
 	.io_outputb = npcm7xx_kcs_outb,
 	.io_updateb = npcm7xx_kcs_updateb,
@@ -186,11 +198,14 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, priv);
 
-	npcm7xx_kcs_enable_channel(kcs_bmc, true);
 	rc = npcm7xx_kcs_config_irq(kcs_bmc, pdev);
 	if (rc)
 		return rc;
 
+	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
+				    KCS_BMC_EVENT_TYPE_IBF);
+	npcm7xx_kcs_enable_channel(kcs_bmc, true);
+
 	rc = kcs_bmc_add_device(kcs_bmc);
 	if (rc) {
 		dev_warn(&pdev->dev, "Failed to register channel %d: %d\n", kcs_bmc->channel, rc);
@@ -211,6 +226,9 @@ static int npcm7xx_kcs_remove(struct platform_device *pdev)
 
 	kcs_bmc_remove_device(kcs_bmc);
 
+	npcm7xx_kcs_enable_channel(kcs_bmc, false);
+	npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
+
 	return 0;
 }