[U-Boot] [PATCH] nvme: Fix PRP Offset Invalid

[Aaron Williams]

I'm sorry about the messed up subject saying [PATCH]. For some reason git 
send-email is mangling the subject line. I'm new to trying to use this method 
to send out patches. This is version 2 of my patch.

-Aaron

On Thursday, August 22, 2019 2:12:32 AM PDT Aaron Williams wrote:
> When large writes take place I saw a Samsung EVO 970+ return a status
> value of 0x13, PRP Offset Invalid.  I tracked this down to the
> improper handling of PRP entries.  The blocks the PRP entries are
> placed in cannot cross a page boundary and thus should be allocated
> on page boundaries.  This is how the Linux kernel driver works.
> 
> With this patch, the PRP pool is allocated on a page boundary and
> other than the very first allocation, the pool size is a multiple of
> the page size.  Each page can hold (4096 / 8) - 1 entries since the
> last entry must point to the next page in the pool.
> 
> Signed-off-by: Aaron Williams <awilliams at marvell.com>
> ---
>  drivers/nvme/nvme.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
> index d4965e2ef6..bc4cf40b40 100644
> --- a/drivers/nvme/nvme.c
> +++ b/drivers/nvme/nvme.c
> @@ -73,6 +73,9 @@ static int nvme_setup_prps(struct nvme_dev *dev, u64
> *prp2, u64 *prp_pool;
>  	int length = total_len;
>  	int i, nprps;
> +	u32 prps_per_page = (page_size >> 3) - 1;
> +	u32 num_pages;
> +
>  	length -= (page_size - offset);
> 
>  	if (length <= 0) {
> @@ -89,15 +92,19 @@ static int nvme_setup_prps(struct nvme_dev *dev, u64
> *prp2, }
> 
>  	nprps = DIV_ROUND_UP(length, page_size);
> +	num_pages = DIV_ROUND_UP(nprps, prps_per_page);
> 
>  	if (nprps > dev->prp_entry_num) {
>  		free(dev->prp_pool);
> -		dev->prp_pool = malloc(nprps << 3);
> +		/* Always increase in increments of pages.  It doesn't 
waste
> +		 * much memory and reduces the number of allocations.
> +		 */
> +		dev->prp_pool = memalign(page_size, num_pages * 
page_size);
>  		if (!dev->prp_pool) {
>  			printf("Error: malloc prp_pool fail\n");
>  			return -ENOMEM;
>  		}
> -		dev->prp_entry_num = nprps;
> +		dev->prp_entry_num = prps_per_page * num_pages;
>  	}
> 
>  	prp_pool = dev->prp_pool;
> @@ -788,14 +795,6 @@ static int nvme_probe(struct udevice *udev)
>  	}
>  	memset(ndev->queues, 0, NVME_Q_NUM * sizeof(struct nvme_queue 
*));
> 
> -	ndev->prp_pool = malloc(MAX_PRP_POOL);
> -	if (!ndev->prp_pool) {
> -		ret = -ENOMEM;
> -		printf("Error: %s: Out of memory!\n", udev->name);
> -		goto free_nvme;
> -	}
> -	ndev->prp_entry_num = MAX_PRP_POOL >> 3;
> -
>  	ndev->cap = nvme_readq(&ndev->bar->cap);
>  	ndev->q_depth = min_t(int, NVME_CAP_MQES(ndev->cap) + 1, 
NVME_Q_DEPTH);
>  	ndev->db_stride = 1 << NVME_CAP_STRIDE(ndev->cap);
> @@ -805,6 +804,15 @@ static int nvme_probe(struct udevice *udev)
>  	if (ret)
>  		goto free_queue;
> 
> +	/* Allocate after the page size is known */
> +	ndev->prp_pool = memalign(ndev->page_size, MAX_PRP_POOL);
> +	if (!ndev->prp_pool) {
> +		ret = -ENOMEM;
> +		printf("Error: %s: Out of memory!\n", udev->name);
> +		goto free_nvme;
> +	}
> +	ndev->prp_entry_num = MAX_PRP_POOL >> 3;
> +
>  	ret = nvme_setup_io_queues(ndev);
>  	if (ret)
>  		goto free_queue;