Re: [PATCH v6 04/32] drm/pagemap: Add DRM pagemap

[Matthew Brost <matthew.brost@intel.com>]

On Tue, Feb 25, 2025 at 03:06:34PM +0000, Matthew Auld wrote:
> On 25/02/2025 04:42, 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
> > v4:
> >   - Fix kernel doc (G.G.)
> > v5:
> >   - s/map_dma/device_map (Thomas)
> >   - s/unmap_dma/device_unmap (Thomas)
> > 
> > Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> > Reviewed-by: Matthew Brost <matthew.brost@intel.com>
> > Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
> > ---
> >   include/drm/drm_pagemap.h | 105 ++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 105 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..2634abb1e8bf
> > --- /dev/null
> > +++ b/include/drm/drm_pagemap.h
> > @@ -0,0 +1,105 @@
> > +/* 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.
> > + */
> 
> Getting some build failures here. I think just needs something like:
> 
>  /**
>   * enum drm_interconnect_protocol - Used to identify an 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.
>   */
> 

Thanks! Will fix.

Matt

> > +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_device_addr - Device address representation.
> > + * @addr: The dma address or driver-defined address for driver private interconnects.
> > + * @proto: The interconnect protocol.
> > + * @order: The page order of the device 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_device_addr {
> > +	dma_addr_t addr;
> > +	u64 proto : 54;
> > +	u64 order : 8;
> > +	u64 dir : 2;
> > +};
> > +
> > +/**
> > + * drm_pagemap_device_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_device_addr encoding the above information.
> > + */
> > +static inline struct drm_pagemap_device_addr
> > +drm_pagemap_device_addr_encode(dma_addr_t addr,
> > +			       enum drm_interconnect_protocol proto,
> > +			       unsigned int order,
> > +			       enum dma_data_direction dir)
> > +{
> > +	return (struct drm_pagemap_device_addr) {
> > +		.addr = addr,
> > +		.proto = proto,
> > +		.order = order,
> > +		.dir = dir,
> > +	};
> > +}
> > +
> > +/**
> > + * struct drm_pagemap_ops: Ops for a drm-pagemap.
> > + */
> > +struct drm_pagemap_ops {
> > +	/**
> > +	 * @device_map: Map for device access or provide a virtual address suitable for
> > +	 *
> > +	 * @dpagemap: The struct drm_pagemap for the page.
> > +	 * @dev: The device mapper.
> > +	 * @page: The page to map.
> > +	 * @order: The page order of the device mapping. (Size is PAGE_SIZE << order).
> > +	 * @dir: The transfer direction.
> > +	 */
> > +	struct drm_pagemap_device_addr (*device_map)(struct drm_pagemap *dpagemap,
> > +						     struct device *dev,
> > +						     struct page *page,
> > +						     unsigned int order,
> > +						     enum dma_data_direction dir);
> > +
> > +	/**
> > +	 * @device_unmap: Unmap a device address previously obtained using @device_map.
> > +	 *
> > +	 * @dpagemap: The struct drm_pagemap for the mapping.
> > +	 * @dev: The device unmapper.
> > +	 * @addr: The device address obtained when mapping.
> > +	 */
> > +	void (*device_unmap)(struct drm_pagemap *dpagemap,
> > +			     struct device *dev,
> > +			     struct drm_pagemap_device_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
>