Re: [PATCH v3 04/30] drm/pagemap: Add DRM pagemap

[Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>]

On 12/18/24 1:33 AM, Matthew Brost wrote:
> From: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> Introduce drm_pagemap ops to map and unmap dma to VRAM resources. In the
> local memory case it's a matter of merely providing an offset into the
> device's physical address. For future p2p the map and unmap functions may
> encode as needed.
> 
> Similar to how dma-buf works, let the memory provider (drm_pagemap) provide
> the mapping functionality.
> 
> v3:
>   - Move to drm level include
> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>   include/drm/drm_pagemap.h | 103 ++++++++++++++++++++++++++++++++++++++
>   1 file changed, 103 insertions(+)
>   create mode 100644 include/drm/drm_pagemap.h
> 
> diff --git a/include/drm/drm_pagemap.h b/include/drm/drm_pagemap.h
> new file mode 100644
> index 000000000000..b6b387b81479
> --- /dev/null
> +++ b/include/drm/drm_pagemap.h
> @@ -0,0 +1,103 @@
> +/* SPDX-License-Identifier: MIT */
> +#ifndef _DRM_PAGEMAP_H_
> +#define _DRM_PAGEMAP_H_
> +
> +#include <linux/dma-direction.h>
> +#include <linux/hmm.h>
> +#include <linux/types.h>
> +
> +struct drm_pagemap;
> +struct device;
> +
> +/**
> + * enum drm_interconnect_protocol - Used to identify an interconnect protocol.
> + */
> +enum drm_interconnect_protocol {
> +	DRM_INTERCONNECT_SYSTEM,    /* DMA map is system pages. */
> +	DRM_INTERCONNECT_PCIE_P2P,  /* DMA map is PCIE P2P */
> +	DRM_INTERCONNECT_DRIVER,    /* DMA map is driver defined */
> +	/* A driver can add private values beyond DRM_INTERCONNECT_DRIVER */
> +};
> +
> +/**
> + * struct drm_pagemap_dma_addr - DMA address representation.
> + * @addr: The dma address or driver-defined address for driver private interconnects.
> + * @proto: The interconnect protocol.
> + * @order: The page order of the dma mapping. (Size is PAGE_SIZE << order).
> + * @dir: The DMA direction.
> + *
> + * Note: There is room for improvement here. We should be able to pack into
> + * 64 bits.
> + */
> +struct drm_pagemap_dma_addr {
> +	dma_addr_t addr;
> +	u64 proto : 54;
> +	u64 order : 8;
> +	u64 dir : 2;
> +};
> +
> +/**
> + * drm_pagemap_dma_addr_encode() - Encode a dma address with metadata
> + * @addr: The dma address or driver-defined address for driver private interconnects.
> + * @proto: The interconnect protocol.
> + * @order: The page order of the dma mapping. (Size is PAGE_SIZE << order).
> + * @dir: The DMA direction.
> + *
> + * Return: A struct drm_pagemap_dma_addr encoding the above information.
> + */
> +static inline struct drm_pagemap_dma_addr
> +drm_pagemap_dma_addr_encode(dma_addr_t addr,
> +			    enum drm_interconnect_protocol proto,
> +			    unsigned int order,
> +			    enum dma_data_direction dir)
> +{
> +	return (struct drm_pagemap_dma_addr) {
> +		.addr = addr,
> +		.proto = proto,
> +		.order = order,
> +		.dir = dir,
> +	};
> +}
> +
> +/**
> + * struct drm_pagemap_ops: Ops for a drm-pagemap.
> + */
Hi,
In the following comment, the protocol should be removed and an 
explanation of order should be added.

Br,
G.G.
> +struct drm_pagemap_ops {
> +	/**
> +	 * @map_dma: Map for dma access or provide a virtual address suitable for
> +	 * @dev.
> +	 * @dpagemap: The struct drm_pagemap for the page.
> +	 * @dev: The dma mapper.
> +	 * @page: The page to map.
> +	 * @dir: The transfer direction.
> +	 * @protocol: The protocol to use.
> +	 */
> +	struct drm_pagemap_dma_addr (*map_dma)(struct drm_pagemap *dpagemap,
> +					       struct device *dev,
> +					       struct page *page,
> +					       unsigned int order,
> +					       enum dma_data_direction dir);
> +
> +	/**
> +	 * @unmap_dma: Unmap a dma address previously obtained using  @map_dma.
> +	 * @dev: The dma unmapper.
> +	 * @addr: The dma address obtained when mapping.
> +	 */
> +	void (*unmap_dma)(struct drm_pagemap *dpagemap,
> +			  struct device *dev,
> +			  struct drm_pagemap_dma_addr addr);
> +
> +};
> +
> +/**
> + * struct drm_pagemap: Additional information for a struct dev_pagemap
> + * used for device p2p handshaking.
> + * @ops: The struct drm_pagemap_ops.
> + * @dev: The struct drevice owning the device-private memory.
> + */
> +struct drm_pagemap {
> +	const struct drm_pagemap_ops *ops;
> +	struct device *dev;
> +};
> +
> +#endif