Re: [PATCH v9 1/4] i2c: tegra: Do not configure DMA if not supported

Jon Hunter
2025-10-28T10:42:02Z

On 28/10/2025 10:00, Akhil R wrote:
> On Fri, 24 Oct 2025 16:20:09 +0100, Jon Hunter wrote:
>> On 01/10/2025 07:47, 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@nvidia.com>
>>> ---
>>> v4 -> v9: Moved the condition down to have all dma checks together.
>>> 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..aa7c0d8c0941 100644
>>> --- a/drivers/i2c/busses/i2c-tegra.c
>>> +++ b/drivers/i2c/busses/i2c-tegra.c
>>> @@ -449,6 +449,11 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
>>> if (IS_VI(i2c_dev))
>>> return 0;
>>>
>>> + 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 (i2c_dev->hw->has_apb_dma) {
>>> if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) {
>>> dev_dbg(i2c_dev->dev, "APB DMA support not enabled\n");
>>
>> What about ACPI based devices?
>
> The of_ function returns false if using ACPI. Since these DMA drivers does
> not support ACPI enumeration currently, we would not require to proceed
> further anyway. But if required we can add an additional check with
> acpi_dma_supported() or similar. Do you suggest adding a check for ACPI?

I was just wondering if it is better to use fwnode_property_present()
instead.

Jon

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