From 8818e865aa35493baf7326f9335b8ec6b7d77df7 Mon Sep 17 00:00:00 2001
From: Icenowy Zheng <icenowy@aosc.io>
Date: Fri, 22 Jun 2018 20:45:36 +0800
Subject: [PATCH] bus: add bus driver for accessing Allwinner A64 DE2

The "Display Engine 2.0" (usually called DE2) on the Allwinner A64 SoC
is different from the ones on other Allwinner SoCs. It requires a SRAM
region to be claimed, otherwise all DE2 subblocks won't be accessible.

Add a bus driver for the Allwinner A64 DE2 part which claims the SRAM
region when probing.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
---
 drivers/bus/Kconfig      | 10 +++++++++
 drivers/bus/Makefile     |  1 +
 drivers/bus/sun50i-de2.c | 48 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+)
 create mode 100644 drivers/bus/sun50i-de2.c

diff --git a/drivers/bus/Kconfig b/drivers/bus/Kconfig
index d1c0b60e9326..1851112ccc29 100644
--- a/drivers/bus/Kconfig
+++ b/drivers/bus/Kconfig
@@ -103,6 +103,16 @@ config SIMPLE_PM_BUS
 	  Controller (BSC, sometimes called "LBSC within Bus Bridge", or
 	  "External Bus Interface") as found on several Renesas ARM SoCs.
 
+config SUN50I_DE2_BUS
+	bool "Allwinner A64 DE2 Bus Driver"
+	  default ARM64
+	  depends on ARCH_SUNXI
+	  select SUNXI_SRAM
+	  help
+	  Say y here to enable support for Allwinner A64 DE2 bus driver. It's
+	  mostly transparent, but a SRAM region needs to be claimed in the SRAM
+	  controller to make the all blocks in the DE2 part accessible.
+
 config SUNXI_RSB
 	tristate "Allwinner sunXi Reduced Serial Bus Driver"
 	  default MACH_SUN8I || MACH_SUN9I || ARM64
diff --git a/drivers/bus/Makefile b/drivers/bus/Makefile
index b8f036cca7ff..ca300b1914ce 100644
--- a/drivers/bus/Makefile
+++ b/drivers/bus/Makefile
@@ -21,6 +21,7 @@ obj-$(CONFIG_OMAP_INTERCONNECT)	+= omap_l3_smx.o omap_l3_noc.o
 
 obj-$(CONFIG_OMAP_OCP2SCP)	+= omap-ocp2scp.o
 obj-$(CONFIG_QCOM_EBI2)		+= qcom-ebi2.o
+obj-$(CONFIG_SUN50I_DE2_BUS)	+= sun50i-de2.o
 obj-$(CONFIG_SUNXI_RSB)		+= sunxi-rsb.o
 obj-$(CONFIG_SIMPLE_PM_BUS)	+= simple-pm-bus.o
 obj-$(CONFIG_TEGRA_ACONNECT)	+= tegra-aconnect.o
diff --git a/drivers/bus/sun50i-de2.c b/drivers/bus/sun50i-de2.c
new file mode 100644
index 000000000000..672518741f86
--- /dev/null
+++ b/drivers/bus/sun50i-de2.c
@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Allwinner A64 Display Engine 2.0 Bus Driver
+ *
+ * Copyright (C) 2018 Icenowy Zheng <icenowy@aosc.io>
+ */
+
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/soc/sunxi/sunxi_sram.h>
+
+static int sun50i_de2_bus_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+
+	ret = sunxi_sram_claim(&pdev->dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Error couldn't map SRAM to device\n");
+		return ret;
+	}
+
+	of_platform_populate(np, NULL, NULL, &pdev->dev);
+
+	return 0;
+}
+
+static int sun50i_de2_bus_remove(struct platform_device *pdev)
+{
+	sunxi_sram_release(&pdev->dev);
+	return 0;
+}
+
+static const struct of_device_id sun50i_de2_bus_of_match[] = {
+	{ .compatible = "allwinner,sun50i-a64-de2", },
+	{ /* sentinel */ }
+};
+
+static struct platform_driver sun50i_de2_bus_driver = {
+	.probe = sun50i_de2_bus_probe,
+	.remove = sun50i_de2_bus_remove,
+	.driver = {
+		.name = "sun50i-de2-bus",
+		.of_match_table = sun50i_de2_bus_of_match,
+	},
+};
+
+builtin_platform_driver(sun50i_de2_bus_driver);