intel_th: msu: Switch over to scatterlist

Instead of using a home-grown array of pointers to the DMA pages, switch
over to scatterlist data types and accessors, which has all the convenient
accessors, can be used to batch-map DMA memory and is convenient for
passing around between different layers, which will be useful when MSU
buffer management has to cross the boundaries of the MSU driver.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hwtracing/intel_th/msu.c b/drivers/hwtracing/intel_th/msu.c
index f5d5cb8..0e7fbef 100644 (file)
--- a/drivers/hwtracing/intel_th/msu.c
+++ b/drivers/hwtracing/intel_th/msu.c
@@ -29,28 +29,18 @@
 #define msc_dev(x) (&(x)->thdev->dev)
 
 /**
- * struct msc_block - multiblock mode block descriptor
- * @bdesc:     pointer to hardware descriptor (beginning of the block)
- * @addr:      physical address of the block
- */
-struct msc_block {
-       struct msc_block_desc   *bdesc;
-       dma_addr_t              addr;
-};
-
-/**
  * struct msc_window - multiblock mode window descriptor
  * @entry:     window list linkage (msc::win_list)
  * @pgoff:     page offset into the buffer that this window starts at
  * @nr_blocks: number of blocks (pages) in this window
- * @block:     array of block descriptors
+ * @sgt:       array of block descriptors
  */
 struct msc_window {
        struct list_head        entry;
        unsigned long           pgoff;
        unsigned int            nr_blocks;
        struct msc              *msc;
-       struct msc_block        block[0];
+       struct sg_table         sgt;
 };
 
 /**
@@ -143,6 +133,24 @@ static inline bool msc_block_is_empty(struct msc_block_desc *bdesc)
        return false;
 }
 
+static inline struct msc_block_desc *
+msc_win_block(struct msc_window *win, unsigned int block)
+{
+       return sg_virt(&win->sgt.sgl[block]);
+}
+
+static inline dma_addr_t
+msc_win_baddr(struct msc_window *win, unsigned int block)
+{
+       return sg_dma_address(&win->sgt.sgl[block]);
+}
+
+static inline unsigned long
+msc_win_bpfn(struct msc_window *win, unsigned int block)
+{
+       return msc_win_baddr(win, block) >> PAGE_SHIFT;
+}
+
 /**
  * msc_oldest_window() - locate the window with oldest data
  * @msc:       MSC device
@@ -168,11 +176,11 @@ static struct msc_window *msc_oldest_window(struct msc *msc)
         * something like 2, in which case we're good
         */
        list_for_each_entry(win, &msc->win_list, entry) {
-               if (win->block[0].addr == win_addr)
+               if (sg_dma_address(win->sgt.sgl) == win_addr)
                        found++;
 
                /* skip the empty ones */
-               if (msc_block_is_empty(win->block[0].bdesc))
+               if (msc_block_is_empty(msc_win_block(win, 0)))
                        continue;
 
                if (found)
@@ -191,7 +199,7 @@ static struct msc_window *msc_oldest_window(struct msc *msc)
 static unsigned int msc_win_oldest_block(struct msc_window *win)
 {
        unsigned int blk;
-       struct msc_block_desc *bdesc = win->block[0].bdesc;
+       struct msc_block_desc *bdesc = msc_win_block(win, 0);
 
        /* without wrapping, first block is the oldest */
        if (!msc_block_wrapped(bdesc))
@@ -202,7 +210,7 @@ static unsigned int msc_win_oldest_block(struct msc_window *win)
         * oldest data for this window.
         */
        for (blk = 0; blk < win->nr_blocks; blk++) {
-               bdesc = win->block[blk].bdesc;
+               bdesc = msc_win_block(win, blk);
 
                if (msc_block_last_written(bdesc))
                        return blk;
@@ -238,7 +246,7 @@ static struct msc_window *msc_next_window(struct msc_window *win)
 
 static struct msc_block_desc *msc_iter_bdesc(struct msc_iter *iter)
 {
-       return iter->win->block[iter->block].bdesc;
+       return msc_win_block(iter->win, iter->block);
 }
 
 static void msc_iter_init(struct msc_iter *iter)
@@ -471,7 +479,7 @@ static void msc_buffer_clear_hw_header(struct msc *msc)
                        offsetof(struct msc_block_desc, hw_tag);
 
                for (blk = 0; blk < win->nr_blocks; blk++) {
-                       struct msc_block_desc *bdesc = win->block[blk].bdesc;
+                       struct msc_block_desc *bdesc = msc_win_block(win, blk);
 
                        memset(&bdesc->hw_tag, 0, hw_sz);
                }
@@ -734,6 +742,40 @@ static struct page *msc_buffer_contig_get_page(struct msc *msc,
        return virt_to_page(msc->base + (pgoff << PAGE_SHIFT));
 }
 
+static int __msc_buffer_win_alloc(struct msc_window *win,
+                                 unsigned int nr_blocks)
+{
+       struct scatterlist *sg_ptr;
+       void *block;
+       int i, ret;
+
+       ret = sg_alloc_table(&win->sgt, nr_blocks, GFP_KERNEL);
+       if (ret)
+               return -ENOMEM;
+
+       for_each_sg(win->sgt.sgl, sg_ptr, nr_blocks, i) {
+               block = dma_alloc_coherent(msc_dev(win->msc)->parent->parent,
+                                         PAGE_SIZE, &sg_dma_address(sg_ptr),
+                                         GFP_KERNEL);
+               if (!block)
+                       goto err_nomem;
+
+               sg_set_buf(sg_ptr, block, PAGE_SIZE);
+       }
+
+       return nr_blocks;
+
+err_nomem:
+       for (i--; i >= 0; i--)
+               dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
+                                 msc_win_block(win, i),
+                                 msc_win_baddr(win, i));
+
+       sg_free_table(&win->sgt);
+
+       return -ENOMEM;
+}
+
 /**
  * msc_buffer_win_alloc() - alloc a window for a multiblock mode
  * @msc:       MSC device
@@ -747,45 +789,48 @@ static struct page *msc_buffer_contig_get_page(struct msc *msc,
 static int msc_buffer_win_alloc(struct msc *msc, unsigned int nr_blocks)
 {
        struct msc_window *win;
-       unsigned long size = PAGE_SIZE;
-       int i, ret = -ENOMEM;
+       int ret = -ENOMEM, i;
 
        if (!nr_blocks)
                return 0;
 
-       win = kzalloc(offsetof(struct msc_window, block[nr_blocks]),
-                     GFP_KERNEL);
+       /*
+        * This limitation hold as long as we need random access to the
+        * block. When that changes, this can go away.
+        */
+       if (nr_blocks > SG_MAX_SINGLE_ALLOC)
+               return -EINVAL;
+
+       win = kzalloc(sizeof(*win), GFP_KERNEL);
        if (!win)
                return -ENOMEM;
 
+       win->msc = msc;
+
        if (!list_empty(&msc->win_list)) {
                struct msc_window *prev = list_last_entry(&msc->win_list,
                                                          struct msc_window,
                                                          entry);
 
+               /* This works as long as blocks are page-sized */
                win->pgoff = prev->pgoff + prev->nr_blocks;
        }
 
-       for (i = 0; i < nr_blocks; i++) {
-               win->block[i].bdesc =
-                       dma_alloc_coherent(msc_dev(msc)->parent->parent, size,
-                                          &win->block[i].addr, GFP_KERNEL);
-
-               if (!win->block[i].bdesc)
-                       goto err_nomem;
+       ret = __msc_buffer_win_alloc(win, nr_blocks);
+       if (ret < 0)
+               goto err_nomem;
 
 #ifdef CONFIG_X86
+       for (i = 0; i < ret; i++)
                /* Set the page as uncached */
-               set_memory_uc((unsigned long)win->block[i].bdesc, 1);
+               set_memory_uc((unsigned long)msc_win_block(win, i), 1);
 #endif
-       }
 
-       win->msc = msc;
-       win->nr_blocks = nr_blocks;
+       win->nr_blocks = ret;
 
        if (list_empty(&msc->win_list)) {
-               msc->base = win->block[0].bdesc;
-               msc->base_addr = win->block[0].addr;
+               msc->base = msc_win_block(win, 0);
+               msc->base_addr = msc_win_baddr(win, 0);
        }
 
        list_add_tail(&win->entry, &msc->win_list);
@@ -794,19 +839,25 @@ static int msc_buffer_win_alloc(struct msc *msc, unsigned int nr_blocks)
        return 0;
 
 err_nomem:
-       for (i--; i >= 0; i--) {
-#ifdef CONFIG_X86
-               /* Reset the page to write-back before releasing */
-               set_memory_wb((unsigned long)win->block[i].bdesc, 1);
-#endif
-               dma_free_coherent(msc_dev(msc)->parent->parent, size,
-                                 win->block[i].bdesc, win->block[i].addr);
-       }
        kfree(win);
 
        return ret;
 }
 
+static void __msc_buffer_win_free(struct msc *msc, struct msc_window *win)
+{
+       int i;
+
+       for (i = 0; i < win->nr_blocks; i++) {
+               struct page *page = sg_page(&win->sgt.sgl[i]);
+
+               page->mapping = NULL;
+               dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
+                                 msc_win_block(win, i), msc_win_baddr(win, i));
+       }
+       sg_free_table(&win->sgt);
+}
+
 /**
  * msc_buffer_win_free() - free a window from MSC's window list
  * @msc:       MSC device
@@ -827,17 +878,13 @@ static void msc_buffer_win_free(struct msc *msc, struct msc_window *win)
                msc->base_addr = 0;
        }
 
-       for (i = 0; i < win->nr_blocks; i++) {
-               struct page *page = virt_to_page(win->block[i].bdesc);
-
-               page->mapping = NULL;
 #ifdef CONFIG_X86
-               /* Reset the page to write-back before releasing */
-               set_memory_wb((unsigned long)win->block[i].bdesc, 1);
+       for (i = 0; i < win->nr_blocks; i++)
+               /* Reset the page to write-back */
+               set_memory_wb((unsigned long)msc_win_block(win, i), 1);
 #endif
-               dma_free_coherent(msc_dev(win->msc)->parent->parent, PAGE_SIZE,
-                                 win->block[i].bdesc, win->block[i].addr);
-       }
+
+       __msc_buffer_win_free(msc, win);
 
        kfree(win);
 }
@@ -871,11 +918,11 @@ static void msc_buffer_relink(struct msc *msc)
                }
 
                for (blk = 0; blk < win->nr_blocks; blk++) {
-                       struct msc_block_desc *bdesc = win->block[blk].bdesc;
+                       struct msc_block_desc *bdesc = msc_win_block(win, blk);
 
                        memset(bdesc, 0, sizeof(*bdesc));
 
-                       bdesc->next_win = next_win->block[0].addr >> PAGE_SHIFT;
+                       bdesc->next_win = msc_win_bpfn(next_win, 0);
 
                        /*
                         * Similarly to last window, last block should point
@@ -883,11 +930,9 @@ static void msc_buffer_relink(struct msc *msc)
                         */
                        if (blk == win->nr_blocks - 1) {
                                sw_tag |= MSC_SW_TAG_LASTBLK;
-                               bdesc->next_blk =
-                                       win->block[0].addr >> PAGE_SHIFT;
+                               bdesc->next_blk = msc_win_bpfn(win, 0);
                        } else {
-                               bdesc->next_blk =
-                                       win->block[blk + 1].addr >> PAGE_SHIFT;
+                               bdesc->next_blk = msc_win_bpfn(win, blk + 1);
                        }
 
                        bdesc->sw_tag = sw_tag;
@@ -1062,7 +1107,7 @@ static struct page *msc_buffer_get_page(struct msc *msc, unsigned long pgoff)
 
 found:
        pgoff -= win->pgoff;
-       return virt_to_page(win->block[pgoff].bdesc);
+       return sg_page(&win->sgt.sgl[pgoff]);
 }
 
 /**