ata: ahci_platform: Add shutdown handler

The newly introduced ahci_platform_shutdown() method is called during
system shutdown to disable host controller DMA and interrupts in order
to avoid potentially corrupting or otherwise interfering with a new
kernel being started with kexec.
Signed-off-by: Nate Watterson <nwatters@codeaurora.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

drivers/ata/ahci_platform.c

@@ -93,6 +93,7 @@ MODULE_DEVICE_TABLE(acpi, ahci_acpi_match);
 static struct platform_driver ahci_driver = {
 	.probe = ahci_probe,
 	.remove = ata_platform_remove_one,
+	.shutdown = ahci_platform_shutdown,
 	.driver = {
 		.name = DRV_NAME,
 		.of_match_table = ahci_of_match,

drivers/ata/libahci_platform.c

@@ -602,6 +602,40 @@ static void ahci_host_stop(struct ata_host *host)
 	ahci_platform_disable_resources(hpriv);
 }
 
+/**
+ * ahci_platform_shutdown - Disable interrupts and stop DMA for host ports
+ * @dev: platform device pointer for the host
+ *
+ * This function is called during system shutdown and performs the minimal
+ * deconfiguration required to ensure that an ahci_platform host cannot
+ * corrupt or otherwise interfere with a new kernel being started with kexec.
+ */
+void ahci_platform_shutdown(struct platform_device *pdev)
+{
+	struct ata_host *host = platform_get_drvdata(pdev);
+	struct ahci_host_priv *hpriv = host->private_data;
+	void __iomem *mmio = hpriv->mmio;
+	int i;
+
+	for (i = 0; i < host->n_ports; i++) {
+		struct ata_port *ap = host->ports[i];
+
+		/* Disable port interrupts */
+		if (ap->ops->freeze)
+			ap->ops->freeze(ap);
+
+		/* Stop the port DMA engines */
+		if (ap->ops->port_stop)
+			ap->ops->port_stop(ap);
+	}
+
+	/* Disable and clear host interrupts */
+	writel(readl(mmio + HOST_CTL) & ~HOST_IRQ_EN, mmio + HOST_CTL);
+	readl(mmio + HOST_CTL); /* flush */
+	writel(GENMASK(host->n_ports, 0), mmio + HOST_IRQ_STAT);
+}
+EXPORT_SYMBOL_GPL(ahci_platform_shutdown);
+
 #ifdef CONFIG_PM_SLEEP
 /**
  * ahci_platform_suspend_host - Suspend an ahci-platform host

include/linux/ahci_platform.h

@@ -36,6 +36,8 @@ int ahci_platform_init_host(struct platform_device *pdev,
 			    const struct ata_port_info *pi_template,
 			    struct scsi_host_template *sht);
 
+void ahci_platform_shutdown(struct platform_device *pdev);
+
 int ahci_platform_suspend_host(struct device *dev);
 int ahci_platform_resume_host(struct device *dev);
 int ahci_platform_suspend(struct device *dev);