[PATCH 10/14] drm/ttm: provide dma aware ttm page pool code V8

[Jerome Glisse]

On Wed, Nov 16, 2011 at 10:50:01AM -0500, Konrad Rzeszutek Wilk wrote:
> > +int ttm_dma_populate(struct ttm_tt *ttm, struct device *dev)
> > +{
> .. snip..
> 
> > +	for (i = 0; i < ttm->num_pages; ++i) {
> > +		ret = ttm_dma_pool_get_pages(pool, ttm, i);
> > +		if (ret != 0) {
> > +			ttm_dma_unpopulate(ttm, dev);
> > +			return -ENOMEM;
> > +		}
> > +
> > +		ret = ttm_mem_global_alloc_page(mem_glob, ttm->pages[i],
> > +						false, false);
> 
> Ok, so we increment it here..
> 
> .. snip..
> > +void ttm_dma_unpopulate(struct ttm_tt *ttm, struct device *dev)
> > +{
> > +	struct dma_pool *pool;
> > +	struct dma_page *d_page;
> > +	enum pool_type type;
> > +	bool is_cached = false;
> > +	unsigned count = 0, i;
> > +	unsigned long irq_flags;
> > +
> > +	type = ttm_to_type(ttm->page_flags, ttm->caching_state);
> > +	pool = ttm_dma_find_pool(dev, type);
> > +	if (!pool) {
> > +		WARN_ON(!pool);
> > +		return;
> > +	}
> > +	is_cached = (ttm_dma_find_pool(pool->dev,
> > +		     ttm_to_type(ttm->page_flags, tt_cached)) == pool);
> > +
> > +	/* make sure pages array match list and count number of pages */
> > +	list_for_each_entry(d_page, &ttm->alloc_list, page_list) {
> > +		ttm->pages[count] = d_page->p;
> > +		count++;
> > +	}
> > +
> > +	spin_lock_irqsave(&pool->lock, irq_flags);
> > +	pool->npages_in_use -= count;
> > +	if (is_cached) {
> > +		pool->nfrees += count;
> > +	} else {
> > +		pool->npages_free += count;
> > +		list_splice(&ttm->alloc_list, &pool->free_list);
> > +		if (pool->npages_free > _manager->options.max_size) {
> > +			count = pool->npages_free - _manager->options.max_size;
> > +		}
> > +	}
> > +	spin_unlock_irqrestore(&pool->lock, irq_flags);
> 
> But we don't do it here.  I think you need:
> 
> 	for (i = 0; i < ttm->num_pages; i++) {
> 		ttm_mem_global_free_page(mem_glob, ttm->pages[i]);
> 
> And it has to be done before ttm_dma_pages_put as at that point the
> pages are truly gone.
> 
> Could actually be done in the '/* make sure pages array match list .."

Actually to avoid the race you need to do it one page at a time. Will
respin with that.

> 
> > +
> > +	if (is_cached) {
> > +		ttm_dma_pages_put(pool, &ttm->alloc_list,
> > +				  ttm->pages, count);
> > +	}
> > +
> > +	INIT_LIST_HEAD(&ttm->alloc_list);
> > +	for (i = 0; i < ttm->num_pages; i++) {
> > +		ttm->pages[i] = NULL;
> > +		ttm->dma_address[i] = 0;
> > +	}