irqchip/qcom-pdc: Allow QCOM_PDC to be loadable as a permanent module

Allows qcom-pdc driver to be loaded as a permanent module

Also, due to the fact that IRQCHIP_DECLARE becomes a no-op when
building as a module, we have to replace it with platform driver
hooks explicitly.

Thanks to Saravana for his help on pointing out the
IRQCHIP_DECLARE issue and guidance on a solution.

Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: Andy Gross <agross@kernel.org>
Cc: Bjorn Andersson <bjorn.andersson@linaro.org>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Maulik Shah <mkshah@codeaurora.org>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Todd Kjos <tkjos@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-arm-msm@vger.kernel.org
Cc: iommu@lists.linux-foundation.org
Cc: linux-gpio@vger.kernel.org
Link: https://lore.kernel.org/r/20200710231824.60699-4-john.stultz@linaro.org

drivers/irqchip/Kconfig

@@ -425,7 +425,7 @@ config GOLDFISH_PIC
          for Goldfish based virtual platforms.
 
 config QCOM_PDC
-	bool "QCOM PDC"
+	tristate "QCOM PDC"
 	depends on ARCH_QCOM
 	select IRQ_DOMAIN_HIERARCHY
 	help

drivers/irqchip/qcom-pdc.c

@@ -11,9 +11,11 @@
 #include <linux/irqdomain.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
+#include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>
+#include <linux/of_irq.h>
 #include <linux/soc/qcom/irq.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
@@ -430,4 +432,28 @@ fail:
 	return ret;
 }
 
-IRQCHIP_DECLARE(qcom_pdc, "qcom,pdc", qcom_pdc_init);
+static int qcom_pdc_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *parent = of_irq_find_parent(np);
+
+	return qcom_pdc_init(np, parent);
+}
+
+static const struct of_device_id qcom_pdc_match_table[] = {
+	{ .compatible = "qcom,pdc" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, qcom_pdc_match_table);
+
+static struct platform_driver qcom_pdc_driver = {
+	.probe = qcom_pdc_probe,
+	.driver = {
+		.name = "qcom-pdc",
+		.of_match_table = qcom_pdc_match_table,
+		.suppress_bind_attrs = true,
+	},
+};
+module_platform_driver(qcom_pdc_driver);
+MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Power Domain Controller");
+MODULE_LICENSE("GPL v2");