[PATCH V2] nvme: Invalidate dcache before submitting admin cmd

[Tom Rini]

On Wed, Jun 10, 2020 at 09:18:23PM +0200, Michael Trimarchi wrote:

> From: Jagan Teki <jagan at amarulasolutions.com>
> 
> 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 <andre.przywara at arm.com>
> Reported-by: Suniel Mahesh <sunil at amarulasolutions.com>
> Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> Signed-off-by: Jagan Teki <jagan at amarulasolutions.com>
> Tested-by: Suniel Mahesh <sunil at amarulasolutions.com>
> Reviewed-by: Bin Meng <bmeng.cn at gmail.com>

Applied (back on June 23rd) to u-boot/master, thanks!

-- 
Tom
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