linux-kernel - Re: [PATCH 0/2] dmaengine: ti: k3-udma: Support for per channel atype

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Date:   Mon, 2 Mar 2020 14:44:28 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        dan.j.williams@...el.com, grygorii.strashko@...com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 0/2] dmaengine: ti: k3-udma: Support for per channel atype

On 18-02-20, 16:31, Peter Ujfalusi wrote:
> Hi,
> 
> The series is on top of the 5.6 update patches:
> https://lore.kernel.org/lkml/20200214091441.27535-1-peter.ujfalusi@ti.com/
> 
> UDMA channels have ATYPE property which tells UDMA on how to treat the pointers
> within descriptors (and TRs).
> The ATYPE defined for j721e are:
> 0: pointers are physical addresses (no translation)
> 1: pointers are intermediate addresses (PVU)
> 2: pointers are virtual addresses (SMMU)
> 
> When Linux is booting within a virtualized environment channels must have the
> ATYPE configured correctly to be able to access memory (ATYPE == 0 is not
> allowed).
> The ATYPE can be different for channels and their ATYPE depends on which
> endpoint they are servicing, but it is not hardwired.
> 
> In order to be able to tell the driver the ATYPE for the channel we need to
> extend the dma-cells in case the device is going to be used in virtualized
> setup.
> 
> Non virtualized setups can still use dma-cells == 1.
> 
> If dma-cells == 2, then the UDMA node must have ti,udma-atype property which
> is used for non slave channels (where no DT binding is exist for a channel).

Applied, thanks

-- 
~Vinod