MALI Panfrost 驱动

代码路径在: src/gallium/drivers/panfrost下，官网目前还不太支持Vulkan

最新的开发活动都在：https://gitlab.freedesktop.org/panfrost/mesa
里面有部分Vulkan的支持。

主要还是实现pipe screen和pipe context，screen主要体现硬件的能力，创建和管理资源；
context可以认为是硬件的一个pipe line的实例，涉及到state的设置，fence等。
另外让pipe loader选择我们新创建的pipe driver。

文件说明

主要有两个文件夹：

src/gallium/drivers/panfrost：

pan_screen: 实现了pipe_screen
pan_context: 实现了pipe_context
pan_resource: 资源相关的放在这里
pan_job: 和硬件相关的job放在这里

src/panfrost/lib, 由于当前Vulkan还没有公共框架，所以和Vulkan公共的代码放在这个文件夹下：

pan_device: 设备管理
pan_bo: buffer object管理
pan_shader: shader管理
pan_tiler:tile管理
pan_texture: texture管理

pan_screen

定义很简单，主要继承下Gallium和device

struct panfrost_screen {
    struct pipe_screen base;
    struct panfrost_device dev;
};

pan_context

关键实现如下：

struct panfrost_context {
    /* Gallium context */
    struct pipe_context base;

    /* Upload manager for small resident GPU-internal data structures, like
     * sampler descriptors. We use an upload manager since the minimum BO
     * size from the kernel is 4kb */
    struct u_upload_mgr *state_uploader;

    /* Sync obj used to keep track of in-flight jobs. */
    uint32_t syncobj;

    /* Bound job batch and map of panfrost_batch_key to job batches */
    struct panfrost_batch *batch;
    struct hash_table *batches;

    /* panfrost_bo -> panfrost_bo_access */
    struct hash_table *accessed_bos;
    struct pipe_framebuffer_state pipe_framebuffer;
    struct panfrost_streamout streamout;
    struct panfrost_constant_buffer constant_buffer[PIPE_SHADER_TYPES];
    struct panfrost_rasterizer *rasterizer;
    struct panfrost_shader_variants *shader[PIPE_SHADER_TYPES];
    struct panfrost_vertex_state *vertex;
    struct pipe_vertex_buffer vertex_buffers[PIPE_MAX_ATTRIBS];
    struct pipe_shader_buffer ssbo[PIPE_SHADER_TYPES][PIPE_MAX_SHADER_BUFFERS];
    struct pipe_image_view images[PIPE_SHADER_TYPES][PIPE_MAX_SHADER_IMAGES];
    struct panfrost_sampler_state *samplers[PIPE_SHADER_TYPES][PIPE_MAX_SAMPLERS];
    struct panfrost_sampler_view *sampler_views[PIPE_SHADER_TYPES][PIPE_MAX_SHADER_SAMPLER_VIEWS];
    struct primconvert_context *primconvert;
    struct blitter_context *blitter;
    struct panfrost_blend_state *blend;
    struct pipe_viewport_state pipe_viewport;
    struct pipe_scissor_state scissor;
    struct pipe_blend_color blend_color;
    struct panfrost_zsa_state *depth_stencil;
    struct pipe_stencil_ref stencil_ref;
    ...
};

基本严格按照渲染的pipeline来的，直观一点如下图：

pan_resource

引用下pipe_resource，通过pipe_screen的pipe_resource和pan_screen关联起来

struct panfrost_resource {
    struct pipe_resource base;
    ...
};

void panfrost_resource_screen_init(struct pipe_screen *pscreen)
{
    struct panfrost_device *dev = pan_device(pscreen);

    bool fake_rgtc = !panfrost_supports_compressed_format(dev, MALI_BC4_UNORM);

    pscreen->resource_create_with_modifiers =
        panfrost_resource_create_with_modifiers;
    pscreen->resource_create = u_transfer_helper_resource_create;
    pscreen->resource_destroy = u_transfer_helper_resource_destroy;
    pscreen->resource_from_handle = panfrost_resource_from_handle;
    pscreen->resource_get_handle = panfrost_resource_get_handle;
    pscreen->transfer_helper = u_transfer_helper_create(&transfer_vtbl,
            true, false,
            fake_rgtc, true);
}

pipe_context类似：

void panfrost_resource_context_init(struct pipe_context *pctx)
{
    pctx->transfer_map = u_transfer_helper_transfer_map;
    pctx->transfer_unmap = u_transfer_helper_transfer_unmap;
    pctx->create_surface = panfrost_create_surface;
    pctx->surface_destroy = panfrost_surface_destroy;
    pctx->resource_copy_region = util_resource_copy_region;
    pctx->blit = panfrost_blit;
    pctx->generate_mipmap = panfrost_generate_mipmap;
    pctx->flush_resource = panfrost_flush_resource;
    pctx->invalidate_resource = panfrost_invalidate_resource;
    pctx->transfer_flush_region = u_transfer_helper_transfer_flush_region;
    pctx->buffer_subdata = u_default_buffer_subdata;
    pctx->texture_subdata = u_default_texture_subdata;
}

pan_job

job都是一批一批提交的，所以主要是panfrost_batch结构，一般属于某个context，实现和硬件强相关。

struct panfrost_batch {
    struct panfrost_context *ctx;
    ...
}

winsys 接口

winsys/panfrost/drm，只用对接drm，创建并返回pipe screen。