lkml.org 
[lkml]   [2019]   [Jul]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH 1/4] csky: Fixup dma_rmb/wmb synchronization problem
On Tue, Jul 30, 2019 at 2:15 PM <guoren@kernel.org> wrote:
>
> From: Guo Ren <ren_guo@c-sky.com>
>
> If arch didn't define dma_r/wmb(), linux will use w/rmb instead. Csky
> use bar.xxx to implement mb() and that will cause problem when sync data
> with dma device, becasue bar.xxx couldn't guarantee bus transactions
> finished at outside bus level. We must use sync.s instead of bar.xxx for
> dma data synchronization and it will guarantee retirement after getting
> the bus bresponse.
>
> Signed-off-by: Guo Ren <ren_guo@c-sky.com>

This change looks good to me, but I think your regular barriers
(mb, rmb, wmb) are still wrong: These are meant to be the superset
of dma_{r,w}mb and smp_{,r,w}mb, and synchronize
against both SMP and DMA interactions.

I suspect you can drop the '.s' for non-SMP builds. What I don't
see is whether you might need to add '.i' for dma_wmb() or
dma_rmb().

Arnd

\
 
 \ /
  Last update: 2019-07-30 15:30    [W:2.069 / U:0.004 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site