/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/prefetch.h>

/**
 * iommu_fill_pdir - Insert coalesced scatter/gather chunks into the I/O Pdir.
 * @ioc: The I/O Controller.
 * @startsg: The scatter/gather list of coalesced chunks.
 * @nents: The number of entries in the scatter/gather list.
 * @hint: The DMA Hint.
 *
 * This function inserts the coalesced scatter/gather list chunks into the
 * I/O Controller's I/O Pdir.
 */ 
static inline unsigned int
iommu_fill_pdir(struct ioc *ioc, struct scatterlist *startsg, int nents, 
                unsigned long hint,
                void (*iommu_io_pdir_entry)(__le64 *, space_t, phys_addr_t,
                                            unsigned long))
{
        struct scatterlist *dma_sg = startsg;   /* pointer to current DMA */
        unsigned int n_mappings = 0;
        unsigned long dma_offset = 0, dma_len = 0;
        __le64 *pdirp = NULL;

        /* Horrible hack.  For efficiency's sake, dma_sg starts one 
         * entry below the true start (it is immediately incremented
         * in the loop) */
         dma_sg--;

        while (nents-- > 0) {
                phys_addr_t paddr;
                long size;

                DBG_RUN_SG(" %d : %08lx %p/%05x\n", nents,
                           (unsigned long)sg_dma_address(startsg),
                           sg_virt(startsg), startsg->length
                );


                /*
                ** Look for the start of a new DMA stream
                */
                
                if (sg_dma_address(startsg) & PIDE_FLAG) {
                        u32 pide = sg_dma_address(startsg) & ~PIDE_FLAG;

                        BUG_ON(pdirp && (dma_len != sg_dma_len(dma_sg)));

                        dma_sg++;

                        dma_len = sg_dma_len(startsg);
                        sg_dma_len(startsg) = 0;
                        dma_offset = (unsigned long) pide & ~IOVP_MASK;
                        n_mappings++;
#if defined(ZX1_SUPPORT)
                        /* Pluto IOMMU IO Virt Address is not zero based */
                        sg_dma_address(dma_sg) = pide | ioc->ibase;
#else
                        /* SBA, ccio, and dino are zero based.
                         * Trying to save a few CPU cycles for most users.
                         */
                        sg_dma_address(dma_sg) = pide;
#endif
                        pdirp = &(ioc->pdir_base[pide >> IOVP_SHIFT]);
                        prefetchw(pdirp);
                }
                
                BUG_ON(pdirp == NULL);
                
                paddr = sg_phys(startsg);
                sg_dma_len(dma_sg) += startsg->length;
                size = startsg->length + dma_offset;
                dma_offset = 0;
#ifdef IOMMU_MAP_STATS
                ioc->msg_pages += startsg->length >> IOVP_SHIFT;
#endif
                do {
                        iommu_io_pdir_entry(pdirp, KERNEL_SPACE, 
                                            paddr, hint);
                        paddr += IOVP_SIZE;
                        size -= IOVP_SIZE;
                        pdirp++;
                } while(unlikely(size > 0));
                startsg++;
        }
        return(n_mappings);
}


/*
** First pass is to walk the SG list and determine where the breaks are
** in the DMA stream. Allocates PDIR entries but does not fill them.
** Returns the number of DMA chunks.
**
** Doing the fill separate from the coalescing/allocation keeps the
** code simpler. Future enhancement could make one pass through
** the sglist do both.
*/

static inline unsigned int
iommu_coalesce_chunks(struct ioc *ioc, struct device *dev,
                struct scatterlist *startsg, int nents,
                int (*iommu_alloc_range)(struct ioc *, struct device *, size_t))
{
        struct scatterlist *contig_sg;     /* contig chunk head */
        unsigned long dma_offset, dma_len; /* start/len of DMA stream */
        unsigned int n_mappings = 0;
        unsigned int max_seg_size = min(dma_get_max_seg_size(dev),
                                        (unsigned)DMA_CHUNK_SIZE);
        unsigned int max_seg_boundary = dma_get_seg_boundary(dev) + 1;
        if (max_seg_boundary)   /* check if the addition above didn't overflow */
                max_seg_size = min(max_seg_size, max_seg_boundary);

        while (nents > 0) {

                /*
                ** Prepare for first/next DMA stream
                */
                contig_sg = startsg;
                dma_len = startsg->length;
                dma_offset = startsg->offset;

                /* PARANOID: clear entries */
                sg_dma_address(startsg) = 0;
                sg_dma_len(startsg) = 0;

                /*
                ** This loop terminates one iteration "early" since
                ** it's always looking one "ahead".
                */
                while(--nents > 0) {
                        unsigned long prev_end, sg_start;

                        prev_end = (unsigned long)sg_virt(startsg) +
                                                        startsg->length;

                        startsg++;
                        sg_start = (unsigned long)sg_virt(startsg);

                        /* PARANOID: clear entries */
                        sg_dma_address(startsg) = 0;
                        sg_dma_len(startsg) = 0;

                        /*
                        ** First make sure current dma stream won't
                        ** exceed max_seg_size if we coalesce the
                        ** next entry.
                        */   
                        if (unlikely(ALIGN(dma_len + dma_offset + startsg->length, IOVP_SIZE) >
                                     max_seg_size))
                                break;

                        /*
                        * Next see if we can append the next chunk (i.e.
                        * it must end on one page and begin on another, or
                        * it must start on the same address as the previous
                        * entry ended.
                        */
                        if (unlikely((prev_end != sg_start) ||
                                ((prev_end | sg_start) & ~PAGE_MASK)))
                                break;
                        
                        dma_len += startsg->length;
                }

                /*
                ** End of DMA Stream
                ** Terminate last VCONTIG block.
                ** Allocate space for DMA stream.
                */
                sg_dma_len(contig_sg) = dma_len;
                dma_len = ALIGN(dma_len + dma_offset, IOVP_SIZE);
                sg_dma_address(contig_sg) =
                        PIDE_FLAG 
                        | (iommu_alloc_range(ioc, dev, dma_len) << IOVP_SHIFT)
                        | dma_offset;
                n_mappings++;
        }

        return n_mappings;
}