[v9] Add I2C support for Tegra264

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

Posted by Kartik Rajput 4 months, 1 week ago

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");
-- 
2.50.1

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

Posted by Jon Hunter 3 months ago

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");


Reviewed-by: Jon Hunter <jonathanh@nvidia.com>

Thanks!
Jon

-- 
nvpublic

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

Posted by Jon Hunter 3 months, 2 weeks ago

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?

Jon

-- 
nvpublic

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

Posted by Akhil R 3 months, 1 week ago

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?

Regards,
Akhil

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

Posted by Jon Hunter 3 months, 1 week ago

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

-- 
nvpublic

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

Posted by Akhil R 3 months, 1 week ago

On Tue, 28 Oct 2025 10:41:54 +0000 Jon Hunter wrote:
> 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:

...

>>>> 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.

I think ACPI does not use 'dmas' property to connect a DMA resource.
It uses FixedDMA or something similar. It may not be helpful to use
fwnode_*() or device_*() check here in that case.

Regards,
Akhil

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

Posted by Jon Hunter 3 months, 1 week ago

On 28/10/2025 13:08, Akhil R wrote:
> On Tue, 28 Oct 2025 10:41:54 +0000 Jon Hunter wrote:
>> 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:
> 
> ...
> 
>>>>> 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.
> 
> I think ACPI does not use 'dmas' property to connect a DMA resource.
> It uses FixedDMA or something similar. It may not be helpful to use
> fwnode_*() or device_*() check here in that case.

OK. Then fine to leave this as-is.

Jon

-- 
nvpublic