1 /* SPDX-License-Identifier: GPL-2.0 */
2 #include <linux/prefetch.h>
3 
4 /**
5  * iommu_fill_pdir - Insert coalesced scatter/gather chunks into the I/O Pdir.
6  * @ioc: The I/O Controller.
7  * @startsg: The scatter/gather list of coalesced chunks.
8  * @nents: The number of entries in the scatter/gather list.
9  * @hint: The DMA Hint.
10  *
11  * This function inserts the coalesced scatter/gather list chunks into the
12  * I/O Controller's I/O Pdir.
13  */
14 static inline unsigned int
15 iommu_fill_pdir(struct ioc *ioc, struct scatterlist *startsg, int nents,
16 		unsigned long hint,
17 		void (*iommu_io_pdir_entry)(u64 *, space_t, unsigned long,
18 					    unsigned long))
19 {
20 	struct scatterlist *dma_sg = startsg;	/* pointer to current DMA */
21 	unsigned int n_mappings = 0;
22 	unsigned long dma_offset = 0, dma_len = 0;
23 	u64 *pdirp = NULL;
24 
25 	/* Horrible hack.  For efficiency's sake, dma_sg starts one
26 	 * entry below the true start (it is immediately incremented
27 	 * in the loop) */
28 	 dma_sg--;
29 
30 	while (nents-- > 0) {
31 		unsigned long vaddr;
32 		long size;
33 
34 		DBG_RUN_SG(" %d : %08lx/%05x %p/%05x\n", nents,
35 			   (unsigned long)sg_dma_address(startsg), cnt,
36 			   sg_virt(startsg), startsg->length
37 		);
38 
39 
40 		/*
41 		** Look for the start of a new DMA stream
42 		*/
43 
44 		if (sg_dma_address(startsg) & PIDE_FLAG) {
45 			u32 pide = sg_dma_address(startsg) & ~PIDE_FLAG;
46 
47 			BUG_ON(pdirp && (dma_len != sg_dma_len(dma_sg)));
48 
49 			dma_sg++;
50 
51 			dma_len = sg_dma_len(startsg);
52 			sg_dma_len(startsg) = 0;
53 			dma_offset = (unsigned long) pide & ~IOVP_MASK;
54 			n_mappings++;
55 #if defined(ZX1_SUPPORT)
56 			/* Pluto IOMMU IO Virt Address is not zero based */
57 			sg_dma_address(dma_sg) = pide | ioc->ibase;
58 #else
59 			/* SBA, ccio, and dino are zero based.
60 			 * Trying to save a few CPU cycles for most users.
61 			 */
62 			sg_dma_address(dma_sg) = pide;
63 #endif
64 			pdirp = &(ioc->pdir_base[pide >> IOVP_SHIFT]);
65 			prefetchw(pdirp);
66 		}
67 
68 		BUG_ON(pdirp == NULL);
69 
70 		vaddr = (unsigned long)sg_virt(startsg);
71 		sg_dma_len(dma_sg) += startsg->length;
72 		size = startsg->length + dma_offset;
73 		dma_offset = 0;
74 #ifdef IOMMU_MAP_STATS
75 		ioc->msg_pages += startsg->length >> IOVP_SHIFT;
76 #endif
77 		do {
78 			iommu_io_pdir_entry(pdirp, KERNEL_SPACE,
79 					    vaddr, hint);
80 			vaddr += IOVP_SIZE;
81 			size -= IOVP_SIZE;
82 			pdirp++;
83 		} while(unlikely(size > 0));
84 		startsg++;
85 	}
86 	return(n_mappings);
87 }
88 
89 
90 /*
91 ** First pass is to walk the SG list and determine where the breaks are
92 ** in the DMA stream. Allocates PDIR entries but does not fill them.
93 ** Returns the number of DMA chunks.
94 **
95 ** Doing the fill separate from the coalescing/allocation keeps the
96 ** code simpler. Future enhancement could make one pass through
97 ** the sglist do both.
98 */
99 
100 static inline unsigned int
101 iommu_coalesce_chunks(struct ioc *ioc, struct device *dev,
102 		struct scatterlist *startsg, int nents,
103 		int (*iommu_alloc_range)(struct ioc *, struct device *, size_t))
104 {
105 	struct scatterlist *contig_sg;	   /* contig chunk head */
106 	unsigned long dma_offset, dma_len; /* start/len of DMA stream */
107 	unsigned int n_mappings = 0;
108 	unsigned int max_seg_size = min(dma_get_max_seg_size(dev),
109 					(unsigned)DMA_CHUNK_SIZE);
110 	unsigned int max_seg_boundary = dma_get_seg_boundary(dev) + 1;
111 	if (max_seg_boundary)	/* check if the addition above didn't overflow */
112 		max_seg_size = min(max_seg_size, max_seg_boundary);
113 
114 	while (nents > 0) {
115 
116 		/*
117 		** Prepare for first/next DMA stream
118 		*/
119 		contig_sg = startsg;
120 		dma_len = startsg->length;
121 		dma_offset = startsg->offset;
122 
123 		/* PARANOID: clear entries */
124 		sg_dma_address(startsg) = 0;
125 		sg_dma_len(startsg) = 0;
126 
127 		/*
128 		** This loop terminates one iteration "early" since
129 		** it's always looking one "ahead".
130 		*/
131 		while(--nents > 0) {
132 			unsigned long prev_end, sg_start;
133 
134 			prev_end = (unsigned long)sg_virt(startsg) +
135 							startsg->length;
136 
137 			startsg++;
138 			sg_start = (unsigned long)sg_virt(startsg);
139 
140 			/* PARANOID: clear entries */
141 			sg_dma_address(startsg) = 0;
142 			sg_dma_len(startsg) = 0;
143 
144 			/*
145 			** First make sure current dma stream won't
146 			** exceed max_seg_size if we coalesce the
147 			** next entry.
148 			*/
149 			if (unlikely(ALIGN(dma_len + dma_offset + startsg->length, IOVP_SIZE) >
150 				     max_seg_size))
151 				break;
152 
153 			/*
154 			* Next see if we can append the next chunk (i.e.
155 			* it must end on one page and begin on another, or
156 			* it must start on the same address as the previous
157 			* entry ended.
158 			*/
159 			if (unlikely((prev_end != sg_start) ||
160 				((prev_end | sg_start) & ~PAGE_MASK)))
161 				break;
162 
163 			dma_len += startsg->length;
164 		}
165 
166 		/*
167 		** End of DMA Stream
168 		** Terminate last VCONTIG block.
169 		** Allocate space for DMA stream.
170 		*/
171 		sg_dma_len(contig_sg) = dma_len;
172 		dma_len = ALIGN(dma_len + dma_offset, IOVP_SIZE);
173 		sg_dma_address(contig_sg) =
174 			PIDE_FLAG
175 			| (iommu_alloc_range(ioc, dev, dma_len) << IOVP_SHIFT)
176 			| dma_offset;
177 		n_mappings++;
178 	}
179 
180 	return n_mappings;
181 }
182 
183