[PATCH] nvme: Enable FUA

[Stefan Agner]

On 2021-09-26 11:12, Jon Lin wrote:
> Most NVME devcies maintain data in internal cache for an uncertain
> times, and u-boot has no method to force NVME to flush cache.
> So this patch adds FUA to avoid data loss caused by power off after data
> programming.

Maybe worth mentioning that FUA stands for Force Unit Access and makes
sure that data has been written to non-volatile storage before command
completion.

It seems to me that volatile cache needs to be explicitly enabled by the
Volatile Write Cache feature. But I guess it could be already enabled by
earlier firmware/on reboot? Setting the FUA bit will make certain that
data land on non-volatile storage in any case. So:

Reviewed-by: Stefan Agner <stefan at agner.ch>

Out of curiosity, has this been a problem in a real world situation?

--
Stefan

> 
> Signed-off-by: Jon Lin <jon.lin at rock-chips.com>
> ---
> 
>  drivers/nvme/nvme.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/nvme/nvme.c b/drivers/nvme/nvme.c
> index f6465ea7f4..5d05cb6e9e 100644
> --- a/drivers/nvme/nvme.c
> +++ b/drivers/nvme/nvme.c
> @@ -761,6 +761,9 @@ static ulong nvme_blk_rw(struct udevice *udev,
> lbaint_t blknr,
>  	c.rw.appmask = 0;
>  	c.rw.metadata = 0;
>  
> +	/* Always enable FUA for data integrity */
> +	c.rw.control |= NVME_RW_FUA;
> +
>  	while (total_lbas) {
>  		if (total_lbas < lbas) {
>  			lbas = (u16)total_lbas;