linux-kernel - Re: [PATCH 0/3] dt-bindings: dma: ti: k3* : Update optional reg regions

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Date:   Fri, 11 Aug 2023 18:16:32 +0300
From:   Péter Ujfalusi <peter.ujfalusi@...il.com>
To:     Vignesh Raghavendra <vigneshr@...com>,
        Vinod Koul <vkoul@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc:     dmaengine@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/3] dt-bindings: dma: ti: k3* : Update optional reg
 regions

Vignesh,

On 10/08/2023 20:43, Vignesh Raghavendra wrote:
> DMAs on TI K3 SoCs have channel configuration registers region which are
> usually hidden from Linux and configured via Device Manager Firmware
> APIs. But certain early SWs like bootloader which run before Device
> Manager is fully up would need to directly configure these registers and
> thus require to be in DT description.
> 
> This add bindings for such configuration regions.  Backward
> compatibility is maintained to existing DT by only mandating existing
> regions to be present and this new region as optional.

These regions were 'hidden' from Linux or other open coded access for a 
reason.
If I recall the main reason is security and the need to make sure that 
the allocation of the channels not been violated.

IMho the boot loader should be no exception and it should be using the 
DM firmware to configure the DMAs.

Or has the security concern been dropped and SW can do whatever it wants?

> 
> Vignesh Raghavendra (3):
>    dt-bindings: dma: ti: k3-bcdma: Describe cfg register regions
>    dt-bindings: dma: ti: k3-pktdma: Describe cfg register regions
>    dt-bindings: dma: ti: k3-udma: Describe cfg register regions
> 
>   .../devicetree/bindings/dma/ti/k3-bcdma.yaml  | 25 +++++++++++++------
>   .../devicetree/bindings/dma/ti/k3-pktdma.yaml | 18 ++++++++++---
>   .../devicetree/bindings/dma/ti/k3-udma.yaml   | 14 ++++++++---
>   3 files changed, 43 insertions(+), 14 deletions(-)
> 

-- 
Péter