linux-kernel - Re: [PATCH v3 2/4] dma: gpi: Add Lock and Unlock TRE support to access SE exclusively

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Message-ID: <ddf48f55-7b9a-4dbd-97f4-6f165d2c12af@quicinc.com>
Date: Wed, 13 Nov 2024 21:36:46 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, <konrad.dybcio@...aro.org>,
        <andersson@...nel.org>, <andi.shyti@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <dmaengine@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
        <conor+dt@...nel.org>, <agross@...nel.org>,
        <devicetree@...r.kernel.org>, <vkoul@...nel.org>, <linux@...blig.org>,
        <dan.carpenter@...aro.org>, <Frank.Li@....com>,
        <konradybcio@...nel.org>, <bryan.odonoghue@...aro.org>,
        <krzk+dt@...nel.org>, <robh@...nel.org>
Subject: Re: [PATCH v3 2/4] dma: gpi: Add Lock and Unlock TRE support to
 access SE exclusively

Thanks Konrad for the review !

On 10/26/2024 12:18 AM, Konrad Dybcio wrote:
> On 27.09.2024 8:31 AM, Mukesh Kumar Savaliya wrote:
>> GSI DMA provides specific TREs namely Lock and Unlock TRE, which
>> provides mutual exclusive access to SE from any of the subsystem
>> (E.g. Apps, TZ, ADSP etc). Lock prevents other subsystems from
>> concurrently performing DMA transfers and avoids disturbance to
>> data path. Basically for shared SE usecase, lock the SE for
>> particular subsystem, complete the transfer, unlock the SE.
>>
>> Apply Lock TRE for the first transfer of shared SE and Apply Unlock
>> TRE for the last transfer.
>>
>> Also change MAX_TRE macro to 5 from 3 because of the two additional TREs.
>>
>> TRE = Transfer Ring Element, refers to the queued descriptor.
>> SE = Serial Engine
>> SS = Subsystems (Apps processor, TZ, ADSP, Modem)
>>
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
>> ---
>>   drivers/dma/qcom/gpi.c           | 37 +++++++++++++++++++++++++++++++-
>>   include/linux/dma/qcom-gpi-dma.h |  6 ++++++
>>   2 files changed, 42 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/dma/qcom/gpi.c b/drivers/dma/qcom/gpi.c
>> index 52a7c8f2498f..120d91234442 100644
>> --- a/drivers/dma/qcom/gpi.c
>> +++ b/drivers/dma/qcom/gpi.c
>> @@ -2,6 +2,7 @@
>>   /*
>>    * Copyright (c) 2017-2020, The Linux Foundation. All rights reserved.
>>    * Copyright (c) 2020, Linaro Limited
>> + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
>>    */
>>   
>>   #include <dt-bindings/dma/qcom-gpi.h>
>> @@ -65,6 +66,14 @@
>>   /* DMA TRE */
>>   #define TRE_DMA_LEN		GENMASK(23, 0)
>>   
>> +/* Lock TRE */
>> +#define TRE_I2C_LOCK		BIT(0)
>> +#define TRE_MINOR_TYPE		GENMASK(19, 16)
>> +#define TRE_MAJOR_TYPE		GENMASK(23, 20)
> 
> Is this solely I2C specific?
> 
No, its generic. So i guess i should rename to TRE_LOCK only, we can use 
for other protocols in future. Thanks!
> Konrad