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

[Matthew Brost]

On Fri, Jan 24, 2025 at 09:19:41AM +0200, Gwan-gyeong Mun wrote:
> 
> 
> On 12/18/24 1:33 AM, Matthew Brost wrote:
> > From: Thomas Hellström <thomas.hellstrom at 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 at intel.com>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom at 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.
> 

Thanks. There a couple of kernel doc errors here too. Will fix.

Matt

> 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
>