linux-kernel - Re: [PATCH v1 1/5] dt-bindings: dmaengine: qcom: gpi: Add additional arg to dma-cell property

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Message-ID: <5f36903a-e21f-4f5b-bc59-ab2bd7cbfb30@quicinc.com>
Date: Fri, 25 Oct 2024 23:55:51 +0530
From: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
To: Vinod Koul <vkoul@...nel.org>
CC: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Andi Shyti <andi.shyti@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König
	<christian.koenig@....com>,
        <cros-qcom-dts-watchers@...omium.org>, <linux-arm-msm@...r.kernel.org>,
        <dmaengine@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <linux-media@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linaro-mm-sig@...ts.linaro.org>, <quic_msavaliy@...cinc.com>,
        <quic_vtanuku@...cinc.com>
Subject: Re: [PATCH v1 1/5] dt-bindings: dmaengine: qcom: gpi: Add additional
 arg to dma-cell property


On 10/16/2024 10:24 AM, Vinod Koul wrote:
> On 15-10-24, 17:37, Jyothi Kumar Seerapu wrote:
>> When high performance with multiple i2c messages in a single transfer
>> is required, employ Block Event Interrupt (BEI) to trigger interrupts
>> after specific messages transfer and the last message transfer,
>> thereby reducing interrupts.
>>
>> For each i2c message transfer, a series of Transfer Request Elements(TREs)
>> must be programmed, including config tre for frequency configuration,
>> go tre for holding i2c address and dma tre for holding dma buffer address,
>> length as per the hardware programming guide. For transfer using BEI,
>> multiple I2C messages may necessitate the preparation of config, go,
>> and tx DMA TREs. However, a channel TRE size of 64 is often insufficient,
>> potentially leading to failures due to inadequate memory space.
>>
>> Add additional argument to dma-cell property for channel TRE size.
>> With this, adjust the channel TRE size via the device tree.
>> The default size is 64, but clients can modify this value based on
>> their specific requirements.
>>
>> Signed-off-by: Jyothi Kumar Seerapu <quic_jseerapu@...cinc.com>
>> ---
>>   Documentation/devicetree/bindings/dma/qcom,gpi.yaml | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/dma/qcom,gpi.yaml b/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
>> index 4df4e61895d2..002495921643 100644
>> --- a/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
>> +++ b/Documentation/devicetree/bindings/dma/qcom,gpi.yaml
>> @@ -54,14 +54,16 @@ properties:
>>       maxItems: 13
>>   
>>     "#dma-cells":
>> -    const: 3
>> +    minItems: 3
>> +    maxItems: 4
>>       description: >
>>         DMA clients must use the format described in dma.txt, giving a phandle
>> -      to the DMA controller plus the following 3 integer cells:
>> +      to the DMA controller plus the following 4 integer cells:
>>         - channel: if set to 0xffffffff, any available channel will be allocated
>>           for the client. Otherwise, the exact channel specified will be used.
>>         - seid: serial id of the client as defined in the SoC documentation.
>>         - client: type of the client as defined in dt-bindings/dma/qcom-gpi.h
>> +      - channel-tre-size: size of the channel TRE (transfer ring element)
> This is a firmware /software property, why should this be in hardware
> description?

This is a software property and here trying to add channel tre size as a 
4th argument of dma-cells property.

In V2, i have reverted the DT and binding changes related to adding new 
argument for dma-cells property and used GPI driver defined value.


Regards,

JyothiKumar


>