Re: [PATCH v2 2/8] dt-bindings: i2c: qcom,i2c-geni: Add support for selecting data transfer mode

Viken Dadhaniya
2025-01-24T15:16:56Z

On 1/24/2025 8:33 PM, Dmitry Baryshkov wrote:
> On Fri, Jan 24, 2025 at 05:52:24PM +0530, Viken Dadhaniya wrote:
>>
>>
>> On 1/24/2025 4:48 PM, Dmitry Baryshkov wrote:
>>> On Fri, Jan 24, 2025 at 04:23:03PM +0530, Viken Dadhaniya wrote:
>>>> Data transfer mode is fixed by TrustZone (TZ), which currently restricts
>>>> developers from modifying the transfer mode from the APPS side.
>>>>
>>>> Document the 'qcom,xfer-mode' properties to select the data transfer mode,
>>>> either GPI DMA (Generic Packet Interface) or non-GPI mode (PIO/CPU DMA).
>>>>
>>>> I2C controller can operate in one of two modes based on the
>>>> 'qcom,xfer-mode' property, and the firmware is loaded accordingly.
>>>
>>> Is it possible to load the firmware after it being loaded by TZ? Is it
>>> possible to change the mode at runtime too?
>>
>> No, firmware can be loaded either from the TZ side or APPS side.
>
> You answer actually reads as "No, yes" (excuse me, non-native here).
> Most likely you mean that it can not be reloaded once either TZ or APPS
> has loaded it.

Yes correct. it can not be reloaded once either TZ or APPS has loaded it.

>
>> In non-GPI mode, the transfer mode will change runtime between PIO and CPU
>> DMA based on the data length.
>>
>> We need to update the device tree property(qcom,xfer-mode) to change the
>> mode between non-GPI and GPI.
>
> So, is it actually possible to change the mode? E.g. if the TZ has
> loaded the firmware and configured SE for PIO/SE DMA, is it possible to
> change it to GPI DMA?

No, if the TZ has loaded the firmware, it is not possible to switch from
non-GPI (PIO/SE DMA) to GPI DMA mode.

>
>>
>>>
>>>>
>>>> Co-developed-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>>> Signed-off-by: Viken Dadhaniya <quic_vdadhani@quicinc.com>
>>>> ---
>>>>
>>>> v1 -> v2:
>>>>
>>>> - Drop 'qcom,load-firmware' property and add 'firmware-name' property in
>>>> qup common driver.
>>>> - Update commit log.
>>>>
>>>> v1 Link: https://lore.kernel.org/linux-kernel/20241204150326.1470749-2-quic_vdadhani@quicinc.com/
>>>> ---
>>>> ---
>>>> .../devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml | 7 +++++++
>>>> 1 file changed, 7 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>>>> index 9f66a3bb1f80..68e4bf0c84d1 100644
>>>> --- a/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>>>> +++ b/Documentation/devicetree/bindings/i2c/qcom,i2c-geni-qcom.yaml
>>>> @@ -66,6 +66,12 @@ properties:
>>>> required-opps:
>>>> maxItems: 1
>>>> + qcom,xfer-mode:
>>>> + description: Set the value to 1 for non-GPI (FIFO/CPU DMA) mode and 3 for GPI DMA mode.
>>>> + The default mode is FIFO.
>>>> + $ref: /schemas/types.yaml#/definitions/uint32
>>>> + enum: [1, 3]
>>>> +
>>>> required:
>>>> - compatible
>>>> - interrupts
>>>> @@ -142,5 +148,6 @@ examples:
>>>> interconnect-names = "qup-core", "qup-config", "qup-memory";
>>>> power-domains = <&rpmhpd SC7180_CX>;
>>>> required-opps = <&rpmhpd_opp_low_svs>;
>>>> + qcom,xfer-mode = <1>;
>>>
>>> What does <1> mean? Please provide corresponding defines.
>>
>> Do we need to add a string instead of a number, like
>> include/dt-bindings/dma/qcom-gpi.h?
>
> You need to '#define FOO_BAR 1', then another one for 3. String is a
> "string", it's not required here (in my opinion).
>

Sure, I will update it in the next patch.