nvme: Invalidate dcache before submitting admin cmd

This patch try to avoids eviction of dirty lines during DMA
transfer. The code right now execute the following step:

- allocate the buffer
- start a dma operation using the non-coherent dma buffer
- invalidate cache lines associated with the buffer
- read the buffer

This can lead to reading back not valid information, because the cache
controller could evict dirty cache lines belonging to the buffer *after*
the DMA operation has started to fill the DRAM.
In order to avoid this, a new invalidation is required *before* starting
the DMA operation. The patch just adds an invalidation before submitting
the DMA command.

Example below shows the nvme disk scan result without the following
patch

=> nvme scan
nvme_get_info_from_identify: nn = 544502629, vwc = 100,
sn = dev_0T, mn = `�\�, fr = t_part, mdts = 105

So, invalidating the cache before submitting the admin command,
fix the cpu read.

Cc: André Przywara <[email protected]>
Reported-by: Suniel Mahesh <[email protected]>
Signed-off-by: Michael Trimarchi <[email protected]>
Signed-off-by: Jagan Teki <[email protected]>
Tested-by: Suniel Mahesh <[email protected]>
Reviewed-by: Bin Meng <[email protected]>

diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
index 0357aba7f1162cd98ade940ce8acbac197cd65a9..fc64d93ab83b7fabe9b9fcad42d7057664ceb2c6 100644 (file)
--- a/drivers/nvme/nvme.c
+++ b/drivers/nvme/nvme.c
@@ -466,6 +466,9 @@ int nvme_identify(struct nvme_dev *dev, unsigned nsid,
 
        c.identify.cns = cpu_to_le32(cns);
 
+       invalidate_dcache_range(dma_addr,
+                               dma_addr + sizeof(struct nvme_id_ctrl));
+
        ret = nvme_submit_admin_cmd(dev, &c, NULL);
        if (!ret)
                invalidate_dcache_range(dma_addr,