nvme: Fix PRP Offset Invalid

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@marvell.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
index d4965e2..47f101e 100644 (file)
--- 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 +92,20 @@ 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 +796,6 @@ 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 +805,15 @@ 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;