Re: [PATCH v2 08/29] drm/xe: Add dma_addr res cursor

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

On Tue, 2024-10-15 at 20:24 -0700, Matthew Brost wrote:
> From: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> 
> Useful for SVM ranges in SRAM and programing page tables.

We should look at providing a better commit message.

> 
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/xe/xe_res_cursor.h | 116
> ++++++++++++++++++++++++++++-
>  drivers/gpu/drm/xe/xe_svm.h        |   4 +
>  2 files changed, 118 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_res_cursor.h
> b/drivers/gpu/drm/xe/xe_res_cursor.h
> index dca374b6521c..3faa3d9adb82 100644
> --- a/drivers/gpu/drm/xe/xe_res_cursor.h
> +++ b/drivers/gpu/drm/xe/xe_res_cursor.h
> @@ -30,13 +30,18 @@
>  #include <drm/ttm/ttm_range_manager.h>
>  #include <drm/ttm/ttm_resource.h>
>  #include <drm/ttm/ttm_tt.h>
> +#include "drm_pagemap.h"
>  
>  #include "xe_bo.h"
>  #include "xe_device.h"
>  #include "xe_macros.h"
> +#include "xe_svm.h"
>  #include "xe_ttm_vram_mgr.h"
>  
> -/* state back for walking over vram_mgr, stolen_mgr, and gtt_mgr
> allocations */
> +/**
> + * struct xe_res_cursor - state for walking over vram_mgr,
> stolen_mgr,
> + * and gtt_mgr allocations
> + */
>  struct xe_res_cursor {
>  	u64 start;
>  	u64 size;
> @@ -44,7 +49,17 @@ struct xe_res_cursor {
>  	void *node;
>  	u32 mem_type;
>  	struct scatterlist *sgl;
> +	/** @dma_addr: Current element in a struct
> drm_pagemap_dma_addr array */
> +	const struct drm_pagemap_dma_addr *dma_addr;
>  	struct drm_buddy *mm;
> +	/**
> +	 * @dma_start: DMA start address for the current segment.
> +	 * This may be different to @dma_addr.addr since elements in
> +	 * the array may be coalesced to a single segment.
> +	 */
> +	u64 dma_start;
> +	/** @dma_seg_size: Size of the current segment. */
> +	u64 dma_seg_size;
>  };
>  
>  static struct drm_buddy *xe_res_get_buddy(struct ttm_resource *res)
> @@ -70,6 +85,7 @@ static inline void xe_res_first(struct ttm_resource
> *res,
>  				struct xe_res_cursor *cur)
>  {
>  	cur->sgl = NULL;
> +	cur->dma_addr = NULL;
>  	if (!res)
>  		goto fallback;
>  
> @@ -141,6 +157,36 @@ static inline void __xe_res_sg_next(struct
> xe_res_cursor *cur)
>  	cur->sgl = sgl;
>  }
>  
> +/**
> + * __xe_res_dma_next() - Advance the cursor when end-of-segment is
> reached
> + * @cur: The cursor
> + */
> +static inline void __xe_res_dma_next(struct xe_res_cursor *cur)
> +{
> +	const struct drm_pagemap_dma_addr *addr = cur->dma_addr;
> +	u64 start = cur->start;
> +
> +	while (start >= cur->dma_seg_size) {
> +		start -= cur->dma_seg_size;
> +		addr++;
> +		cur->dma_seg_size = PAGE_SIZE << addr->order;
> +	}
> +	cur->dma_start = addr->addr;
> +
> +	/* Coalesce array_elements */
> +	while (cur->dma_seg_size - start < cur->remaining) {
> +		if (cur->dma_start + cur->dma_seg_size !=
> addr[1].addr ||
> +		    addr->proto != addr[1].proto)
> +			break;
> +		addr++;
> +		cur->dma_seg_size += PAGE_SIZE << addr->order;
> +	}
> +
> +	cur->dma_addr = addr;
> +	cur->start = start;
> +	cur->size = cur->dma_seg_size - start;
> +}
> +
>  /**
>   * xe_res_first_sg - initialize a xe_res_cursor with a scatter
> gather table
>   *
> @@ -160,11 +206,42 @@ static inline void xe_res_first_sg(const struct
> sg_table *sg,
>  	cur->start = start;
>  	cur->remaining = size;
>  	cur->size = 0;
> +	cur->dma_addr = NULL;
>  	cur->sgl = sg->sgl;
>  	cur->mem_type = XE_PL_TT;
>  	__xe_res_sg_next(cur);
>  }
>  
> +/**
> + * xe_res_first_dma - initialize a xe_res_cursor with dma_addr array
> + *
> + * @dma_addr: struct drm_pagemap_dma_addr array to walk
> + * @start: Start of the range
> + * @size: Size of the range
> + * @cur: cursor object to initialize
> + *
> + * Start walking over the range of allocations between @start and
> @size.
> + */
> +static inline void xe_res_first_dma(const struct
> drm_pagemap_dma_addr *dma_addr,
> +				    u64 start, u64 size,
> +				    struct xe_res_cursor *cur)
> +{
> +	XE_WARN_ON(!dma_addr);
> +	XE_WARN_ON(!IS_ALIGNED(start, PAGE_SIZE) ||
> +		   !IS_ALIGNED(size, PAGE_SIZE));
> +
> +	cur->node = NULL;
> +	cur->start = start;
> +	cur->remaining = size;
> +	cur->dma_seg_size = PAGE_SIZE << dma_addr->order;
> +	cur->dma_start = 0;
> +	cur->size = 0;
> +	cur->dma_addr = dma_addr;
> +	__xe_res_dma_next(cur);
> +	cur->sgl = NULL;
> +	cur->mem_type = XE_PL_TT;
> +}
> +
>  /**
>   * xe_res_next - advance the cursor
>   *
> @@ -191,6 +268,12 @@ static inline void xe_res_next(struct
> xe_res_cursor *cur, u64 size)
>  		return;
>  	}
>  
> +	if (cur->dma_addr) {
> +		cur->start += size;
> +		__xe_res_dma_next(cur);
> +		return;
> +	}
> +
>  	if (cur->sgl) {
>  		cur->start += size;
>  		__xe_res_sg_next(cur);
> @@ -232,6 +315,35 @@ static inline void xe_res_next(struct
> xe_res_cursor *cur, u64 size)
>   */
>  static inline u64 xe_res_dma(const struct xe_res_cursor *cur)
>  {
> -	return cur->sgl ? sg_dma_address(cur->sgl) + cur->start :
> cur->start;
> +	if (cur->dma_addr)
> +		return cur->dma_start + cur->start;
> +	else if (cur->sgl)
> +		return sg_dma_address(cur->sgl) + cur->start;
> +	else
> +		return cur->start;
> +}
> +
> +/**
> + * xe_res_is_vram() - Whether the cursor current dma address points
> to
> + * same-device VRAM
> + * @cur: The cursor.
> + *
> + * Return: true iff the address returned by xe_res_dma() points to
> internal vram.
> + */
> +static inline bool xe_res_is_vram(const struct xe_res_cursor *cur)
> +{
> +	if (cur->dma_addr)
> +		return cur->dma_addr->proto == XE_INTERCONNECT_VRAM;
> +
> +	switch (cur->mem_type) {
> +	case XE_PL_STOLEN:
> +	case XE_PL_VRAM0:
> +	case XE_PL_VRAM1:
> +		return true;
> +	default:
> +		break;
> +	}
> +
> +	return false;
>  }
>  #endif
> diff --git a/drivers/gpu/drm/xe/xe_svm.h
> b/drivers/gpu/drm/xe/xe_svm.h
> index 979f2322eeba..376e86876a11 100644
> --- a/drivers/gpu/drm/xe/xe_svm.h
> +++ b/drivers/gpu/drm/xe/xe_svm.h
> @@ -6,6 +6,10 @@
>  #ifndef _XE_SVM_H_
>  #define _XE_SVM_H_
>  
> +#include "drm_pagemap.h"
> +
> +#define XE_INTERCONNECT_VRAM DRM_INTERCONNECT_DRIVER
> +
>  struct xe_vm;
>  
>  int xe_svm_init(struct xe_vm *vm);