[PATCH v1 0/2] ata: Fixes related to edge trigger latch for ahci_xgene driver.

[PATCH v1 0/2] ata: Fixes related to edge trigger latch for ahci_xgene driver.

[Suman Tripathi]

This patch set implements a workaround for an errate in the APM
X-Gene SATA host controller with edge interrupt. The HOST_IRQ_STAT
misses the edge interrupt from the PORT_IRQ_STAT when clearing the
HOST_IRQ_STAT and reporting the PORT_IRQ_STAT happens in same clock
cycle. It also implements the capability to override generic interrupt
handler.

v1 change:
* Implement the capability for LDD to override interrupt handler.

* ahci_xgene driver implements the edge trigger interrupt handler.

Signed-off-by: Suman Tripathi <stripathi@apm.com>


Suman Tripathi (2):
  libahci: Implement the capability to override the generic ahci
    interrupt handler
  ahci_xgene: Implement the workaround to fix the missing of edge
    interrupt for HOST_IRQ_STAT

 drivers/ata/ahci.h       |    2 +
 drivers/ata/ahci_xgene.c |   84 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/ata/libahci.c    |   18 ++++++---
 3 files changed, 98 insertions(+), 6 deletions(-)

[PATCH v1 1/2] libahci: Implement the capability to override the generic ahci interrupt handler

[Suman Tripathi]

This patch implements the capability to override the generic
ahci interrupt handler so that LDD drivers can implement there
own interrupt handler routines.

Signed-off-by: Suman Tripathi <stripathi-qTEPVZfXA3Y@public.gmane.org>
---
 drivers/ata/ahci.h    |    2 ++
 drivers/ata/libahci.c |   18 ++++++++++++------
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/ata/ahci.h b/drivers/ata/ahci.h
index 45586c1..f59d517 100644
--- a/drivers/ata/ahci.h
+++ b/drivers/ata/ahci.h
@@ -352,6 +352,7 @@ struct ahci_host_priv {
 	 * be overridden anytime before the host is activated.
 	 */
 	void			(*start_engine)(struct ata_port *ap);
+	irqreturn_t 		(*ahci_irq_intr)(int irq, void *dev_instance);
 };

 extern int ahci_ignore_sss;
@@ -400,6 +401,7 @@ int ahci_reset_em(struct ata_host *host);
 void ahci_print_info(struct ata_host *host, const char *scc_s);
 int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht);
 void ahci_error_handler(struct ata_port *ap);
+u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked);

 static inline void __iomem *__ahci_port_base(struct ata_host *host,
 					     unsigned int port_no)
diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
index 096064c..cc1f774 100644
--- a/drivers/ata/libahci.c
+++ b/drivers/ata/libahci.c
@@ -1832,7 +1832,7 @@ static irqreturn_t ahci_multi_irqs_intr(int irq, void *dev_instance)
 	return IRQ_WAKE_THREAD;
 }

-static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
+u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)
 {
 	unsigned int i, handled = 0;

@@ -1858,6 +1858,7 @@ static u32 ahci_handle_port_intr(struct ata_host *host, u32 irq_masked)

 	return handled;
 }
+EXPORT_SYMBOL_GPL(ahci_handle_port_intr);

 static irqreturn_t ahci_single_edge_irq_intr(int irq, void *dev_instance)
 {
@@ -2517,16 +2518,21 @@ int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht)
 {
 	struct ahci_host_priv *hpriv = host->private_data;
 	int irq = hpriv->irq;
+	irqreturn_t (*ahci_irq_handler)(int irq, void *dev_instance);
 	int rc;

 	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI)
 		rc = ahci_host_activate_multi_irqs(host, irq, sht);
-	else if (hpriv->flags & AHCI_HFLAG_EDGE_IRQ)
-		rc = ata_host_activate(host, irq, ahci_single_edge_irq_intr,
-				       IRQF_SHARED, sht);
-	else
-		rc = ata_host_activate(host, irq, ahci_single_level_irq_intr,
+	else {
+		ahci_irq_handler = hpriv->ahci_irq_intr ? hpriv->ahci_irq_intr :
+				   (hpriv->flags & AHCI_HFLAG_EDGE_IRQ ?
+				   ahci_single_edge_irq_intr :
+				   ahci_single_level_irq_intr);
+
+		rc = ata_host_activate(host, irq, ahci_irq_handler,
 				       IRQF_SHARED, sht);
+	}
+
 	return rc;
 }
 EXPORT_SYMBOL_GPL(ahci_host_activate);
--
1.7.1

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[PATCH v1 2/2] ahci_xgene: Implement the workaround to fix the missing of edge interrupt for HOST_IRQ_STAT

[Suman Tripathi]

Due to H/W errata, the HOST_IRQ_STAT register misses the edge interrupt
when clearing the HOST_IRQ_STAT register and hardware reporting the
PORT_IRQ_STAT register at the same clock cycle.

Signed-off-by: Suman Tripathi <stripathi@apm.com>
---
 drivers/ata/ahci_xgene.c |   84 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 84 insertions(+), 0 deletions(-)

diff --git a/drivers/ata/ahci_xgene.c b/drivers/ata/ahci_xgene.c
index e2c6d9e..4df7a00 100644
--- a/drivers/ata/ahci_xgene.c
+++ b/drivers/ata/ahci_xgene.c
@@ -548,6 +548,89 @@ softreset_retry:
 	return rc;
 }

+/**
+ * xgene_ahci_handle_broken_edge_irq - Handle the broken irq.
+ * @ata_host: Host that recieved the irq
+ * @irq_masked: HOST_IRQ_STAT value
+ *
+ * For hardware with broken edge trigger latch
+ * the HOST_IRQ_STAT register misses the edge interrupt
+ * when clearing of HOST_IRQ_STAT register and hardware
+ * reporting the PORT_IRQ_STAT register at the
+ * same clock cycle.
+ * As such, the algorithm below outlines the workaround.
+ *
+ * 1. Read HOST_IRQ_STAT register and save the state.
+ * 2. Clear the HOST_IRQ_STAT register.
+ * 3. Read back the HOST_IRQ_STAT register.
+ * 4. If HOST_IRQ_STAT register equals to zero, then
+ *    traverse the rest of port's PORT_IRQ_STAT register
+ *    to check if an interrupt is triggered at that point else
+ *    go to step 6.
+ * 5. If PORT_IRQ_STAT register of rest ports is not equal to zero
+ *    then update the state of HOST_IRQ_STAT saved in step 1.
+ * 6. Handle port interrupts.
+ * 7. Exit
+ */
+static int xgene_ahci_handle_broken_edge_irq(struct ata_host *host,
+					     u32 irq_masked)
+{
+	struct ahci_host_priv *hpriv = host->private_data;
+	void __iomem *port_mmio;
+	int i;
+
+	if (!readl(hpriv->mmio + HOST_IRQ_STAT)) {
+		for (i = 0; i < host->n_ports; i++) {
+			if (irq_masked & (1 << i))
+				continue;
+
+			port_mmio = ahci_port_base(host->ports[i]);
+			if (readl(port_mmio + PORT_IRQ_STAT))
+				irq_masked |= (1 << i);
+		}
+	}
+
+	return ahci_handle_port_intr(host, irq_masked);
+}
+
+static irqreturn_t xgene_ahci_irq_intr(int irq, void *dev_instance)
+{
+	struct ata_host *host = dev_instance;
+	struct ahci_host_priv *hpriv;
+	unsigned int rc = 0;
+	void __iomem *mmio;
+	u32 irq_stat, irq_masked;
+
+	VPRINTK("ENTER\n");
+
+	hpriv = host->private_data;
+	mmio = hpriv->mmio;
+
+	/* sigh.  0xffffffff is a valid return from h/w */
+	irq_stat = readl(mmio + HOST_IRQ_STAT);
+	if (!irq_stat)
+		return IRQ_NONE;
+
+	irq_masked = irq_stat & hpriv->port_map;
+
+	spin_lock(&host->lock);
+
+	/*
+	 * HOST_IRQ_STAT behaves as edge triggered latch meaning that
+	 * it should be cleared before all the port events are cleared.
+	 */
+	writel(irq_stat, mmio + HOST_IRQ_STAT);
+
+	rc = xgene_ahci_handle_broken_edge_irq(host, irq_masked);
+
+	spin_unlock(&host->lock);
+
+	VPRINTK("EXIT\n");
+
+	return IRQ_RETVAL(rc);
+
+}
+
 static struct ata_port_operations xgene_ahci_v1_ops = {
 	.inherits = &ahci_ops,
 	.host_stop = xgene_ahci_host_stop,
@@ -780,6 +863,7 @@ skip_clk_phy:
 		break;
 	case XGENE_AHCI_V2:
 		hpriv->flags |= AHCI_HFLAG_YES_FBS | AHCI_HFLAG_EDGE_IRQ;
+		hpriv->ahci_irq_intr = xgene_ahci_irq_intr;
 		break;
 	default:
 		break;
--
1.7.1

Re: [PATCH v1 1/2] libahci: Implement the capability to override the generic ahci interrupt handler

[Tejun Heo]

Hello, Suman.

Your mails ended up in spam again and it looks to be from SPF failure.

  Received-SPF: softfail (google.com: domain of transitioning stripath@apm.com does not designate 198.145.29.136 as permitted sender) client-ip=198.145.29.136;
  Authentication-Results: mx.google.com;
	 spf=softfail (google.com: domain of transitioning stripath@apm.com does not designate 198.145.29.136 as permitted sender) smtp.mailfrom=stripath@apm.com;
	 dmarc=fail (p=QUARANTINE dis=NONE) header.from=apm.com

Can you please look into it?

On Thu, Jan 14, 2016 at 11:00:23AM +0530, Suman Tripathi wrote:
>  static irqreturn_t ahci_single_edge_irq_intr(int irq, void *dev_instance)
>  {
> @@ -2517,16 +2518,21 @@ int ahci_host_activate(struct ata_host *host, struct scsi_host_template *sht)
>  {
>  	struct ahci_host_priv *hpriv = host->private_data;
>  	int irq = hpriv->irq;
> +	irqreturn_t (*ahci_irq_handler)(int irq, void *dev_instance);
>  	int rc;
> 
>  	if (hpriv->flags & AHCI_HFLAG_MULTI_MSI)
>  		rc = ahci_host_activate_multi_irqs(host, irq, sht);
> -	else if (hpriv->flags & AHCI_HFLAG_EDGE_IRQ)
> -		rc = ata_host_activate(host, irq, ahci_single_edge_irq_intr,
> -				       IRQF_SHARED, sht);
> -	else
> -		rc = ata_host_activate(host, irq, ahci_single_level_irq_intr,
> +	else {
> +		ahci_irq_handler = hpriv->ahci_irq_intr ? hpriv->ahci_irq_intr :
> +				   (hpriv->flags & AHCI_HFLAG_EDGE_IRQ ?
> +				   ahci_single_edge_irq_intr :
> +				   ahci_single_level_irq_intr);
> +
> +		rc = ata_host_activate(host, irq, ahci_irq_handler,
>  				       IRQF_SHARED, sht);
> +	}
> +

So, if we have ->ahci_irq_intr, we don't need AHCI_HFLAG_EDGE_IRQ at
all, right?  Just initialize ->ahci_irq_intr to
ahci_single_level_irq_intr and let specific drivers overrie it?

Thanks.

-- 
tejun