[U-Boot] [PATCH 7/8] nvme: Handle zero Maximum Data Transfer Size (MDTS)

Tom Rini trini at konsulko.com
Thu Aug 10 01:31:21 UTC 2017

On Thu, Aug 03, 2017 at 02:31:02AM -0700, Bin Meng wrote:

> Maximum Data Transfer Size (MDTS) field indicates the maximum
> data transfer size between the host and the controller. The
> host should not submit a command that exceeds this transfer
> size. The value is in units of the minimum memory page size
> and is reported as a power of two (2^n).
> The spec also says: a value of 0h indicates no restrictions
> on transfer size. On the real NVMe card this is normally not
> 0 due to hardware restrictions, but with QEMU emulated NVMe
> device it reports as 0. In nvme_blk_read/write() below we
> have the following algorithm for maximum number of logic
> blocks per transfer:
> u16 lbas = 1 << (dev->max_transfer_shift - ns->lba_shift);
> dev->max_transfer_shift being 0 will for sure cause lbas to
> overflow. Let's use 20. With this fix, the NVMe driver works
> on QEMU emulated NVMe device.
> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>

Reviewed-by: Tom Rini <trini at konsulko.com>

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