[PATCH v2 1/5] drm/format-helper: Add struct drm_xfrm_buf to cache format conversion

[Thomas Zimmermann <tzimmermann@suse.de>]

Hold temporary memory for format conversion in an instance of struct
drm_xfrm_buf. Update internal helpers of DRM's format-conversion code
accordingly. Drivers will later be able to keep this cache across
display updates.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/gpu/drm/drm_format_helper.c | 111 +++++++++++++++++++++++++---
 include/drm/drm_format_helper.h     |  46 ++++++++++++
 2 files changed, 146 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/drm_format_helper.c b/drivers/gpu/drm/drm_format_helper.c
index f93a4efcee909..029ca7893260a 100644
--- a/drivers/gpu/drm/drm_format_helper.c
+++ b/drivers/gpu/drm/drm_format_helper.c
@@ -17,9 +17,93 @@
 #include <drm/drm_format_helper.h>
 #include <drm/drm_framebuffer.h>
 #include <drm/drm_fourcc.h>
+#include <drm/drm_managed.h>
 #include <drm/drm_print.h>
 #include <drm/drm_rect.h>
 
+static void drm_xfrm_buf_init_release(struct drm_device *dev, void *res)
+{
+	struct drm_xfrm_buf *buf = res;
+
+	drm_xfrm_buf_release(buf);
+}
+
+/**
+ * drmm_xfrm_buf_init - Initialize xfrm buffer with managed cleanup
+ * @dev: The DRM device
+ * @buf: The xfrm buffer to initialize
+ *
+ * Clears all fields in struct drm_xfrm_buf and installs a DRM release
+ * action for the buffer. The buffer will be empty with no preallocated
+ * resources.
+ *
+ * Returns:
+ * 0 on success, or a negative errno code otherwise.
+ */
+int drmm_xfrm_buf_init(struct drm_device *dev, struct drm_xfrm_buf *buf)
+{
+	buf->mem = NULL;
+	buf->size = 0;
+	buf->preallocated = false;
+
+	return drmm_add_action_or_reset(dev, drm_xfrm_buf_init_release, buf);
+}
+EXPORT_SYMBOL(drmm_xfrm_buf_init);
+
+/**
+ * drm_xfrm_buf_reserve - Allocates storage in an xfrm buffer
+ * @buf: The xfrm buffer
+ * @new_size: The minimum allocation size
+ * @flags: Flags for kmalloc()
+ *
+ * Allocates at least @new_size bytes and returns a pointer to the memory
+ * range. After calling this function, previously returned memory blocks
+ * are invalid. It's best to collect all memory requirements of a format
+ * conversion and call this function once to allocate the range.
+ *
+ * Returns:
+ * A pointer to the allocated memory range, or a pointer-encoded errno code otherwise.
+ */
+void *drm_xfrm_buf_reserve(struct drm_xfrm_buf *buf, size_t new_size, gfp_t flags)
+{
+	void *mem;
+
+	if (new_size <= buf->size)
+		goto out;
+	else if (buf->preallocated)
+		return NULL;
+
+	mem = krealloc(buf->mem, new_size, flags);
+	if (!mem)
+		return NULL;
+
+	buf->mem = mem;
+	buf->size = new_size;
+
+out:
+	return buf->mem;
+}
+EXPORT_SYMBOL(drm_xfrm_buf_reserve);
+
+/**
+ * drm_xfrm_buf_release - Releases an xfrm buffer's storage
+ * @buf: The xfrm buffer
+ *
+ * Releases the memory range references by the xfrm buffer. After
+ * this call, all pointers to the memory are invalid. Prefer
+ * drmm_xfrm_buffer_init() for cleaning up and unloading a driver.
+ */
+void drm_xfrm_buf_release(struct drm_xfrm_buf *buf)
+{
+	if (buf->preallocated)
+		return;
+
+	kfree(buf->mem);
+	buf->mem = NULL;
+	buf->size = 0;
+}
+EXPORT_SYMBOL(drm_xfrm_buf_release);
+
 static unsigned int clip_offset(const struct drm_rect *clip, unsigned int pitch, unsigned int cpp)
 {
 	return clip->y1 * pitch + clip->x1 * cpp;
@@ -45,6 +129,7 @@ EXPORT_SYMBOL(drm_fb_clip_offset);
 static int __drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
 			 const void *vaddr, const struct drm_framebuffer *fb,
 			 const struct drm_rect *clip, bool vaddr_cached_hint,
+			 struct drm_xfrm_buf *xfrm,
 			 void (*xfrm_line)(void *dbuf, const void *sbuf, unsigned int npixels))
 {
 	unsigned long linepixels = drm_rect_width(clip);
@@ -60,7 +145,7 @@ static int __drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_p
 	 * one line at a time.
 	 */
 	if (!vaddr_cached_hint) {
-		stmp = kmalloc(sbuf_len, GFP_KERNEL);
+		stmp = drm_xfrm_buf_reserve(xfrm, sbuf_len, GFP_KERNEL);
 		if (!stmp)
 			return -ENOMEM;
 	}
@@ -79,8 +164,6 @@ static int __drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_p
 		dst += dst_pitch;
 	}
 
-	kfree(stmp);
-
 	return 0;
 }
 
@@ -88,6 +171,7 @@ static int __drm_fb_xfrm(void *dst, unsigned long dst_pitch, unsigned long dst_p
 static int __drm_fb_xfrm_toio(void __iomem *dst, unsigned long dst_pitch, unsigned long dst_pixsize,
 			      const void *vaddr, const struct drm_framebuffer *fb,
 			      const struct drm_rect *clip, bool vaddr_cached_hint,
+			      struct drm_xfrm_buf *xfrm,
 			      void (*xfrm_line)(void *dbuf, const void *sbuf, unsigned int npixels))
 {
 	unsigned long linepixels = drm_rect_width(clip);
@@ -101,9 +185,9 @@ static int __drm_fb_xfrm_toio(void __iomem *dst, unsigned long dst_pitch, unsign
 	void *dbuf;
 
 	if (vaddr_cached_hint) {
-		dbuf = kmalloc(dbuf_len, GFP_KERNEL);
+		dbuf = drm_xfrm_buf_reserve(xfrm, dbuf_len, GFP_KERNEL);
 	} else {
-		dbuf = kmalloc(stmp_off + sbuf_len, GFP_KERNEL);
+		dbuf = drm_xfrm_buf_reserve(xfrm, stmp_off + sbuf_len, GFP_KERNEL);
 		stmp = dbuf + stmp_off;
 	}
 	if (!dbuf)
@@ -124,8 +208,6 @@ static int __drm_fb_xfrm_toio(void __iomem *dst, unsigned long dst_pitch, unsign
 		dst += dst_pitch;
 	}
 
-	kfree(dbuf);
-
 	return 0;
 }
 
@@ -139,17 +221,24 @@ static int drm_fb_xfrm(struct iosys_map *dst,
 	static const unsigned int default_dst_pitch[DRM_FORMAT_MAX_PLANES] = {
 		0, 0, 0, 0
 	};
+	struct drm_xfrm_buf tmp = DRM_XFRM_BUF_INIT;
+	int ret;
 
 	if (!dst_pitch)
 		dst_pitch = default_dst_pitch;
 
 	/* TODO: handle src in I/O memory here */
 	if (dst[0].is_iomem)
-		return __drm_fb_xfrm_toio(dst[0].vaddr_iomem, dst_pitch[0], dst_pixsize[0],
-					  src[0].vaddr, fb, clip, vaddr_cached_hint, xfrm_line);
+		ret = __drm_fb_xfrm_toio(dst[0].vaddr_iomem, dst_pitch[0], dst_pixsize[0],
+					 src[0].vaddr, fb, clip, vaddr_cached_hint, &tmp,
+					 xfrm_line);
 	else
-		return __drm_fb_xfrm(dst[0].vaddr, dst_pitch[0], dst_pixsize[0],
-				     src[0].vaddr, fb, clip, vaddr_cached_hint, xfrm_line);
+		ret = __drm_fb_xfrm(dst[0].vaddr, dst_pitch[0], dst_pixsize[0],
+				    src[0].vaddr, fb, clip, vaddr_cached_hint, &tmp,
+				    xfrm_line);
+	drm_xfrm_buf_release(&tmp);
+
+	return ret;
 }
 
 /**
diff --git a/include/drm/drm_format_helper.h b/include/drm/drm_format_helper.h
index 291deb09475bb..245a5edc4735a 100644
--- a/include/drm/drm_format_helper.h
+++ b/include/drm/drm_format_helper.h
@@ -15,6 +15,52 @@ struct drm_rect;
 
 struct iosys_map;
 
+/**
+ * struct drm_xfrm_buf - Stores transformation and conversion state
+ *
+ * DRM helpers for format conversion store temporary state in
+ * struct drm_xfrm_buf. The buffer's resources can be reused
+ * among multiple conversion operations.
+ *
+ * All fields are considered private.
+ */
+struct drm_xfrm_buf {
+	void *mem;
+	size_t size;
+	bool preallocated;
+};
+
+/**
+ * DRM_XFRM_BUF_INIT - Initializer for struct drm_xfrm_buf
+ *
+ * Initializes an instance of struct drm_xfrm_buf to default
+ * values.
+ */
+#define DRM_XFRM_BUF_INIT { \
+		.mem = NULL, \
+		.size = 0, \
+		.preallocated = false, \
+	}
+
+/**
+ * DRM_XFRM_BUF_INIT_PREALLOCATED - Initializer for struct drm_xfrm_buf
+ * @_mem: The preallocated memory area
+ * @_size: The number of bytes in _mem
+ *
+ * Initializes an instance of struct drm_xfrm_buf to preallocated
+ * storage. The caller is responsible for a releases the provided
+ * memory range.
+ */
+#define DRM_XFRM_BUF_INIT_PREALLOCATED(_mem, _size) { \
+		.mem = (_mem), \
+		.size = (_size), \
+		.preallocated = true, \
+	}
+
+int drmm_xfrm_buf_init(struct drm_device *dev, struct drm_xfrm_buf *buf);
+void *drm_xfrm_buf_reserve(struct drm_xfrm_buf *buf, size_t new_size, gfp_t flags);
+void drm_xfrm_buf_release(struct drm_xfrm_buf *buf);
+
 unsigned int drm_fb_clip_offset(unsigned int pitch, const struct drm_format_info *format,
 				const struct drm_rect *clip);
 
-- 
2.42.0