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SubjectRe: [PATCH 1/2] mmc: let the dma map ops handle bouncing
Hi Christoph,

On Thu, 11 Apr 2019 at 09:10, Christoph Hellwig <hch@lst.de> wrote:
>
> Just like we do for all other block drivers. Especially as the limit
> imposed at the moment might be way to pessimistic for iommus.

I would appreciate some information in the changelog, as it's quite
unclear of what this change really means.

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
> drivers/mmc/core/queue.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index 7c364a9c4eeb..eb9c0692062c 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -354,18 +354,15 @@ static const struct blk_mq_ops mmc_mq_ops = {
> static void mmc_setup_queue(struct mmc_queue *mq, struct mmc_card *card)
> {
> struct mmc_host *host = card->host;
> - u64 limit = BLK_BOUNCE_HIGH;
> unsigned block_size = 512;
>
> - if (mmc_dev(host)->dma_mask && *mmc_dev(host)->dma_mask)
> - limit = (u64)dma_max_pfn(mmc_dev(host)) << PAGE_SHIFT;
> -
> blk_queue_flag_set(QUEUE_FLAG_NONROT, mq->queue);
> blk_queue_flag_clear(QUEUE_FLAG_ADD_RANDOM, mq->queue);
> if (mmc_can_erase(card))
> mmc_queue_setup_discard(mq->queue, card);
>
> - blk_queue_bounce_limit(mq->queue, limit);
> + if (!mmc_dev(host)->dma_mask || !*mmc_dev(host)->dma_mask)
> + blk_queue_bounce_limit(mq->queue, BLK_BOUNCE_HIGH);

So this means we are not going to set a bounce limit for the queue, in
case we have a dma mask.

Why isn't that needed no more? Whats has changed?

> blk_queue_max_hw_sectors(mq->queue,
> min(host->max_blk_count, host->max_req_size / 512));
> blk_queue_max_segments(mq->queue, host->max_segs);
> --
> 2.20.1
>

Kind regards
Uffe

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