Re: [PATCH v2 4/8] dt-bindings: serial: Add support for selecting data transfer mode

Dmitry Baryshkov
2025-01-29T02:21:34Z

On Mon, Jan 27, 2025 at 05:24:21PM +0100, Krzysztof Kozlowski wrote:
> On 27/01/2025 15:27, Dmitry Baryshkov wrote:
> > On Mon, Jan 27, 2025 at 08:02:12AM +0100, Krzysztof Kozlowski wrote:
> >> On 24/01/2025 11:53, Viken Dadhaniya wrote:
> >>> Data transfer mode is fixed by TrustZone (TZ), which currently restricts
> >>> developers from modifying the transfer mode from the APPS side.
> >>>
> >>> Document the 'qcom,xfer-mode' properties to select the data transfer mode,
> >>> either GPI DMA (Generic Packet Interface) or non-GPI mode (PIO/CPU DMA).
> >>>
> >>> UART controller can operate in one of two modes based on the
> >>> 'qcom,xfer-mode' property, and the firmware is loaded accordingly.
> >>>
> >>> Co-developed-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
> >>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
> >>> Signed-off-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
> >>> ---
> >>>
> >>> v1 -> v2:
> >>>
> >>> - Drop 'qcom,load-firmware' property and add 'firmware-name' property in
> >>> qup common driver.
> >>> - Update commit log.
> >>>
> >>> v1 Link: https://lore.kernel.org/linux-kernel/20241204150326.1470749-4-quic_vdadhani@quicinc.com/
> >>> ---
> >>> ---
> >>> .../devicetree/bindings/serial/qcom,serial-geni-qcom.yaml | 8 ++++++++
> >>> 1 file changed, 8 insertions(+)
> >>>
> >>> diff --git a/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
> >>> index dd33794b3534..383773b32e47 100644
> >>> --- a/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
> >>> +++ b/Documentation/devicetree/bindings/serial/qcom,serial-geni-qcom.yaml
> >>> @@ -56,6 +56,13 @@ properties:
> >>> reg:
> >>> maxItems: 1
> >>>
> >>> + qcom,xfer-mode:
> >>> + description: Set the value to 1 for non-GPI (FIFO/CPU DMA) mode and 3 for GPI DMA mode.
> >>> + The default mode is FIFO.
> >>> + $ref: /schemas/types.yaml#/definitions/uint32
> >>> + enum: [1, 3]
> >>> +
> >>> +
> >>
> >> Just one blank line, but anyway, this property should not be in three
> >> places. Do you really expect that each of serial engines within one
> >> GeniQUP will be configured differently by TZ?
> >
> > Yes, each SE is configured separately and it's quite frequent when
> > different SEs have different DMA configuration.
>
> Well, I checked at sm8550 and sm8650 and each pair of SE - which shares
> resources - has the same DMAs, so I would not call it frequent. Care to
> bring an example where same serial engines have different DMAs and
> different TZ? We do not talk about single QUP.

Well, I don't have access to the latest sm8550 / sm8650 devcfg sources.
I checked the RB5 ones. As far as I understand out of 14 enabled SEs
only two are configured for the GSI DMA, others should use FIFO / SE
DMA. Same applies to the SM8250 MTP devices. Checking the RB1 / RB2
setup also shows 3 out of 6 SEs being set for GSI.

>
> Anyway, if you need property per node, this has to be shared schema.
>
> Best regards,
> Krzysztof

--
With best wishes
Dmitry