drm/imagination: Add skeleton PowerVR driver

This adds the basic skeleton of the driver. The driver registers
itself with DRM on probe. Ioctl handlers are currently implemented
as stubs.

Changes since v8:
- Corrected license identifiers

Changes since v5:
- Update compatible string & description to match marketing name
- Checkpatch fixes in to/from_pvr_device/file macros

Changes since v3:
- Clarify supported GPU generations in driver description
- Use drm_dev_unplug() when removing device
- Change from_* and to_* functions to macros
- Fix IS_PTR/PTR_ERR confusion in pvr_probe()
- Remove err_out labels in favour of direct returning
- Remove specific am62 compatible match string
- Drop MODULE_FIRMWARE()

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/fed8a77e29620a61aed2684f802339759082cf1b.1700668843.git.donald.robson@imgtec.com
Signed-off-by: Maxime Ripard <mripard@kernel.org>

1 files changed, 153 insertions, 0 deletions

diff --git a/drivers/gpu/drm/imagination/pvr_device.h b/drivers/gpu/drm/imagination/pvr_device.h
new file mode 100644
index 000000000000..d3629164a629
--- /dev/null
+++ b/drivers/gpu/drm/imagination/pvr_device.h
@@ -0,0 +1,153 @@
+/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
+/* Copyright (c) 2023 Imagination Technologies Ltd. */
+
+#ifndef PVR_DEVICE_H
+#define PVR_DEVICE_H
+
+#include <drm/drm_device.h>
+#include <drm/drm_file.h>
+#include <drm/drm_mm.h>
+
+#include <linux/bits.h>
+#include <linux/compiler_attributes.h>
+#include <linux/compiler_types.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+
+/**
+ * struct pvr_device - powervr-specific wrapper for &struct drm_device
+ */
+struct pvr_device {
+	/**
+	 * @base: The underlying &struct drm_device.
+	 *
+	 * Do not access this member directly, instead call
+	 * from_pvr_device().
+	 */
+	struct drm_device base;
+};
+
+/**
+ * struct pvr_file - powervr-specific data to be assigned to &struct
+ * drm_file.driver_priv
+ */
+struct pvr_file {
+	/**
+	 * @file: A reference to the parent &struct drm_file.
+	 *
+	 * Do not access this member directly, instead call from_pvr_file().
+	 */
+	struct drm_file *file;
+
+	/**
+	 * @pvr_dev: A reference to the powervr-specific wrapper for the
+	 *           associated device. Saves on repeated calls to
+	 *           to_pvr_device().
+	 */
+	struct pvr_device *pvr_dev;
+};
+
+#define from_pvr_device(pvr_dev) (&(pvr_dev)->base)
+
+#define to_pvr_device(drm_dev) container_of_const(drm_dev, struct pvr_device, base)
+
+#define from_pvr_file(pvr_file) ((pvr_file)->file)
+
+#define to_pvr_file(file) ((file)->driver_priv)
+
+/**
+ * DOC: IOCTL validation helpers
+ *
+ * To validate the constraints imposed on IOCTL argument structs, a collection
+ * of macros and helper functions exist in ``pvr_device.h``.
+ *
+ * Of the current helpers, it should only be necessary to call
+ * PVR_IOCTL_UNION_PADDING_CHECK() directly. This macro should be used once in
+ * every code path which extracts a union member from a struct passed from
+ * userspace.
+ */
+
+/**
+ * pvr_ioctl_union_padding_check() - Validate that the implicit padding between
+ * the end of a union member and the end of the union itself is zeroed.
+ * @instance: Pointer to the instance of the struct to validate.
+ * @union_offset: Offset into the type of @instance of the target union. Must
+ * be 64-bit aligned.
+ * @union_size: Size of the target union in the type of @instance. Must be
+ * 64-bit aligned.
+ * @member_size: Size of the target member in the target union specified by
+ * @union_offset and @union_size. It is assumed that the offset of the target
+ * member is zero relative to @union_offset. Must be 64-bit aligned.
+ *
+ * You probably want to use PVR_IOCTL_UNION_PADDING_CHECK() instead of calling
+ * this function directly, since that macro abstracts away much of the setup,
+ * and also provides some static validation. See its docs for details.
+ *
+ * Return:
+ *  * %true if every byte between the end of the used member of the union and
+ *    the end of that union is zeroed, or
+ *  * %false otherwise.
+ */
+static __always_inline bool
+pvr_ioctl_union_padding_check(void *instance, size_t union_offset,
+			      size_t union_size, size_t member_size)
+{
+	/*
+	 * void pointer arithmetic is technically illegal - cast to a byte
+	 * pointer so this addition works safely.
+	 */
+	void *padding_start = ((u8 *)instance) + union_offset + member_size;
+	size_t padding_size = union_size - member_size;
+
+	return !memchr_inv(padding_start, 0, padding_size);
+}
+
+/**
+ * PVR_STATIC_ASSERT_64BIT_ALIGNED() - Inline assertion for 64-bit alignment.
+ * @static_expr_: Target expression to evaluate.
+ *
+ * If @static_expr_ does not evaluate to a constant integer which would be a
+ * 64-bit aligned address (i.e. a multiple of 8), compilation will fail.
+ *
+ * Return:
+ * The value of @static_expr_.
+ */
+#define PVR_STATIC_ASSERT_64BIT_ALIGNED(static_expr_)                     \
+	({                                                                \
+		static_assert(((static_expr_) & (sizeof(u64) - 1)) == 0); \
+		(static_expr_);                                           \
+	})
+
+/**
+ * PVR_IOCTL_UNION_PADDING_CHECK() - Validate that the implicit padding between
+ * the end of a union member and the end of the union itself is zeroed.
+ * @struct_instance_: An expression which evaluates to a pointer to a UAPI data
+ * struct.
+ * @union_: The name of the union member of @struct_instance_ to check. If the
+ * union member is nested within the type of @struct_instance_, this may
+ * contain the member access operator (".").
+ * @member_: The name of the member of @union_ to assess.
+ *
+ * This is a wrapper around pvr_ioctl_union_padding_check() which performs
+ * alignment checks and simplifies things for the caller.
+ *
+ * Return:
+ *  * %true if every byte in @struct_instance_ between the end of @member_ and
+ *    the end of @union_ is zeroed, or
+ *  * %false otherwise.
+ */
+#define PVR_IOCTL_UNION_PADDING_CHECK(struct_instance_, union_, member_)     \
+	({                                                                   \
+		typeof(struct_instance_) __instance = (struct_instance_);    \
+		size_t __union_offset = PVR_STATIC_ASSERT_64BIT_ALIGNED(     \
+			offsetof(typeof(*__instance), union_));              \
+		size_t __union_size = PVR_STATIC_ASSERT_64BIT_ALIGNED(       \
+			sizeof(__instance->union_));                         \
+		size_t __member_size = PVR_STATIC_ASSERT_64BIT_ALIGNED(      \
+			sizeof(__instance->union_.member_));                 \
+		pvr_ioctl_union_padding_check(__instance, __union_offset,    \
+					      __union_size, __member_size);  \
+	})
+
+#endif /* PVR_DEVICE_H */