drm/imagination: Get GPU resources

Acquire clock and register resources, and enable/map as appropriate.

Changes since v8:
- Corrected license identifiers

Changes since v3:
- Remove regulator resource (not used on supported platform)
- Use devm helpers
- Use devm_clk_get_optional() for optional clocks
- Don't prepare clocks on resource acquisition
- Drop pvr_device_clk_core_get_freq() helper
- Drop pvr_device_reg_fini()
- Drop NULLing of clocks in pvr_device_clk_init()
- Use dev_err_probe() on clock acquisition failure
- Remove PVR_CR_READ/WRITE helper macros
- Improve documentation for GPU clocks
- Remove regs resource (not used in this commit)

Co-developed-by: Frank Binns <frank.binns@imgtec.com>
Signed-off-by: Frank Binns <frank.binns@imgtec.com>
Co-developed-by: Matt Coster <matt.coster@imgtec.com>
Signed-off-by: Matt Coster <matt.coster@imgtec.com>
Signed-off-by: Sarah Walker <sarah.walker@imgtec.com>
Signed-off-by: Donald Robson <donald.robson@imgtec.com>
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/579027bd5be4eb3218c9784050ded2326ecbc352.1700668843.git.donald.robson@imgtec.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>

drivers/gpu/drm/imagination/pvr_device.c

@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/* Copyright (c) 2023 Imagination Technologies Ltd. */
+
+#include "pvr_device.h"
+
+#include <drm/drm_print.h>
+
+#include <linux/clk.h>
+#include <linux/compiler_attributes.h>
+#include <linux/compiler_types.h>
+#include <linux/dma-mapping.h>
+#include <linux/err.h>
+#include <linux/gfp.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+
+/**
+ * pvr_device_reg_init() - Initialize kernel access to a PowerVR device's
+ * control registers.
+ * @pvr_dev: Target PowerVR device.
+ *
+ * Sets struct pvr_device->regs.
+ *
+ * This method of mapping the device control registers into memory ensures that
+ * they are unmapped when the driver is detached (i.e. no explicit cleanup is
+ * required).
+ *
+ * Return:
+ *  * 0 on success, or
+ *  * Any error returned by devm_platform_ioremap_resource().
+ */
+static int
+pvr_device_reg_init(struct pvr_device *pvr_dev)
+{
+	struct drm_device *drm_dev = from_pvr_device(pvr_dev);
+	struct platform_device *plat_dev = to_platform_device(drm_dev->dev);
+	void __iomem *regs;
+
+	pvr_dev->regs = NULL;
+
+	regs = devm_platform_ioremap_resource(plat_dev, 0);
+	if (IS_ERR(regs))
+		return dev_err_probe(drm_dev->dev, PTR_ERR(regs),
+				     "failed to ioremap gpu registers\n");
+
+	pvr_dev->regs = regs;
+
+	return 0;
+}
+
+/**
+ * pvr_device_clk_init() - Initialize clocks required by a PowerVR device
+ * @pvr_dev: Target PowerVR device.
+ *
+ * Sets struct pvr_device->core_clk, struct pvr_device->sys_clk and
+ * struct pvr_device->mem_clk.
+ *
+ * Three clocks are required by the PowerVR device: core, sys and mem. On
+ * return, this function guarantees that the clocks are in one of the following
+ * states:
+ *
+ *  * All successfully initialized,
+ *  * Core errored, sys and mem uninitialized,
+ *  * Core deinitialized, sys errored, mem uninitialized, or
+ *  * Core and sys deinitialized, mem errored.
+ *
+ * Return:
+ *  * 0 on success,
+ *  * Any error returned by devm_clk_get(), or
+ *  * Any error returned by devm_clk_get_optional().
+ */
+static int pvr_device_clk_init(struct pvr_device *pvr_dev)
+{
+	struct drm_device *drm_dev = from_pvr_device(pvr_dev);
+	struct clk *core_clk;
+	struct clk *sys_clk;
+	struct clk *mem_clk;
+
+	core_clk = devm_clk_get(drm_dev->dev, "core");
+	if (IS_ERR(core_clk))
+		return dev_err_probe(drm_dev->dev, PTR_ERR(core_clk),
+				     "failed to get core clock\n");
+
+	sys_clk = devm_clk_get_optional(drm_dev->dev, "sys");
+	if (IS_ERR(sys_clk))
+		return dev_err_probe(drm_dev->dev, PTR_ERR(core_clk),
+				     "failed to get sys clock\n");
+
+	mem_clk = devm_clk_get_optional(drm_dev->dev, "mem");
+	if (IS_ERR(mem_clk))
+		return dev_err_probe(drm_dev->dev, PTR_ERR(core_clk),
+				     "failed to get mem clock\n");
+
+	pvr_dev->core_clk = core_clk;
+	pvr_dev->sys_clk = sys_clk;
+	pvr_dev->mem_clk = mem_clk;
+
+	return 0;
+}
+
+/**
+ * pvr_device_init() - Initialize a PowerVR device
+ * @pvr_dev: Target PowerVR device.
+ *
+ * If this function returns successfully, the device will have been fully
+ * initialized. Otherwise, any parts of the device initialized before an error
+ * occurs will be de-initialized before returning.
+ *
+ * NOTE: The initialization steps currently taken are the bare minimum required
+ *       to read from the control registers. The device is unlikely to function
+ *       until further initialization steps are added. [This note should be
+ *       removed when that happens.]
+ *
+ * Return:
+ *  * 0 on success,
+ *  * Any error returned by pvr_device_reg_init(),
+ *  * Any error returned by pvr_device_clk_init(), or
+ *  * Any error returned by pvr_device_gpu_init().
+ */
+int
+pvr_device_init(struct pvr_device *pvr_dev)
+{
+	int err;
+
+	/* Enable and initialize clocks required for the device to operate. */
+	err = pvr_device_clk_init(pvr_dev);
+	if (err)
+		return err;
+
+	/* Map the control registers into memory. */
+	return pvr_device_reg_init(pvr_dev);
+}
+
+/**
+ * pvr_device_fini() - Deinitialize a PowerVR device
+ * @pvr_dev: Target PowerVR device.
+ */
+void
+pvr_device_fini(struct pvr_device *pvr_dev)
+{
+	/*
+	 * Deinitialization stages are performed in reverse order compared to
+	 * the initialization stages in pvr_device_init().
+	 */
+}