linux-kernel - Re: [PATCH v8 1/4] i2c: tegra: Do not configure DMA if not supported

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Message-ID: <21f71c22-8957-43cc-a99b-158366467654@nvidia.com>
Date: Thu, 18 Sep 2025 12:40:18 +0530
From: Kartik Rajput <kkartik@...dia.com>
To: Jon Hunter <jonathanh@...dia.com>, akhilrajeev@...dia.com,
 andi.shyti@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, thierry.reding@...il.com, ldewangan@...dia.com,
 digetx@...il.com, linux-i2c@...r.kernel.org, devicetree@...r.kernel.org,
 linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 1/4] i2c: tegra: Do not configure DMA if not supported

On 17/09/25 19:38, Jon Hunter wrote:
> 
> On 17/09/2025 09:56, Kartik Rajput wrote:
>> On Tegra264, not all I2C controllers have the necessary interface to
>> GPC DMA, this causes failures when function tegra_i2c_init_dma()
>> is called.
>>
>> Ensure that "dmas" device-tree property is present before initializing
>> DMA in function tegra_i2c_init_dma().
>>
>> Signed-off-by: Kartik Rajput <kkartik@...dia.com>
>> ---
>> v2 -> v4:
>>     * Add debug print if DMA is not supported by the I2C controller.
>> v1 -> v2:
>>     * Update commit message to clarify that some I2C controllers may
>>       not have the necessary interface to GPC DMA.
>> ---
>>   drivers/i2c/busses/i2c-tegra.c | 5 +++++
>>   1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
>> index e533460bccc3..d908e5e3f0af 100644
>> --- a/drivers/i2c/busses/i2c-tegra.c
>> +++ b/drivers/i2c/busses/i2c-tegra.c
>> @@ -446,6 +446,11 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
>>       u32 *dma_buf;
>>       int err;
>> +    if (!of_property_present(i2c_dev->dev->of_node, "dmas")) {
>> +        dev_dbg(i2c_dev->dev, "DMA not available, falling back to PIO\n");
>> +        return 0;
>> +    }
>> +
>>       if (IS_VI(i2c_dev))
>>           return 0;
> 
> No issue with this change, but we have a few checks for DMA support in this function and so it would be nice to have them altogether.
> 
> Jon
> 

Ack.

Thanks,
Kartik