Re: [PATCH 23/29] memstick: jmb38x_ms: use DMA for all TPCs with len greater that 8 by default

[Alex Dubov]

--- On Fri, 22/10/10, Maxim Levitsky <maximlevitsky@xxxxxxxxx> wrote:

> From: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
> Subject: [PATCH 23/29] memstick: jmb38x_ms: use DMA for all TPCs with len greater that 8 by default
> To: "Alex Dubov" <oakad@xxxxxxxxx>
> Cc: "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>, "LKML" <linux-kernel@xxxxxxxxxxxxxxx>, "Maxim Levitsky" <maximlevitsky@xxxxxxxxx>
> Received: Friday, 22 October, 2010, 4:53 PM
> This is to workaround a wierd
> hardware bug:
> 
> If PIO write is used, and then after it DMA write is used,
> DMA
> engine stops doing writes.
> That condition even persists after device reset.
> 
> To be maxumum safe, we do dma to a scratch page
> and memcpy from/to it.
> 
> Besides this change should just improve performance.
> 
> Signed-off-by: Maxim Levitsky <maximlevitsky@xxxxxxxxx>
> ---

I have not noticed this one before, and for all I know the driver was
tested at Jmicron.
Can you explain the issue a bit more?



      
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