Re: [PATCH v5 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing between two subsystems

[Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>]

On 12/16/2024 5:40 PM, Konrad Dybcio wrote:
> On 15.12.2024 9:59 AM, Mukesh Kumar Savaliya wrote:
>> Hi Konrad,
>>
>> On 12/13/2024 6:35 PM, Konrad Dybcio wrote:
>>> On 29.11.2024 3:43 PM, Mukesh Kumar Savaliya wrote:
>>>> Add support to share I2C controller in multiprocessor system in a mutually
>>>> exclusive way. Use "qcom,shared-se" flag in a particular i2c instance node
>>>> if the usecase requires i2c controller to be shared.
>>>>
>>>> Sharing of I2C SE(Serial engine) is possible only for GSI mode as client
>>>> from each processor can queue transfers over its own GPII Channel. For
>>>> non GSI mode, we should force disable this feature even if set by user
>>>> from DT by mistake.
>>>>
>>>> I2C driver just need to mark first_msg and last_msg flag to help indicate
>>>> GPI driver to take lock and unlock TRE there by protecting from concurrent
>>>> access from other EE or Subsystem.
>>>>
>>>> gpi_create_i2c_tre() function at gpi.c will take care of adding Lock and
>>>> Unlock TRE for the respective transfer operations.
>>>>
>>>> Since the GPIOs are also shared between two SS, do not unconfigure them
>>>> during runtime suspend. This will allow other SS to continue to transfer
>>>> the data without any disturbance over the IO lines.
>>>>
>>>> For example, Assume an I2C EEPROM device connected with an I2C controller.
>>>> Each client from ADSP and APPS processor can perform i2c transactions
>>>> without any disturbance from each other.
>>>>
>>>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>>> ---
>>>>    drivers/i2c/busses/i2c-qcom-geni.c | 22 +++++++++++++++++++---
>>>>    1 file changed, 19 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
>>>> index 7a22e1f46e60..ccf9933e2dad 100644
>>>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>>>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>>>> @@ -1,5 +1,6 @@
>>>>    // SPDX-License-Identifier: GPL-2.0
>>>>    // Copyright (c) 2017-2018, The Linux Foundation. All rights reserved.
>>>> +// Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved.
>>>>      #include <linux/acpi.h>
>>>>    #include <linux/clk.h>
>>>> @@ -617,6 +618,7 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>>>>        peripheral.clk_div = itr->clk_div;
>>>>        peripheral.set_config = 1;
>>>>        peripheral.multi_msg = false;
>>>> +    peripheral.shared_se = gi2c->se.shared_geni_se;
>>>>          for (i = 0; i < num; i++) {
>>>>            gi2c->cur = &msgs[i];
>>>> @@ -627,6 +629,8 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>>>>            if (i < num - 1)
>>>>                peripheral.stretch = 1;
>>>>    +        peripheral.first_msg = (i == 0);
>>>> +        peripheral.last_msg = (i == num - 1);
>>>>            peripheral.addr = msgs[i].addr;
>>>>              ret =  geni_i2c_gpi(gi2c, &msgs[i], &config,
>>>> @@ -815,6 +819,11 @@ static int geni_i2c_probe(struct platform_device *pdev)
>>>>            gi2c->clk_freq_out = KHZ(100);
>>>>        }
>>>>    +    if (of_property_read_bool(pdev->dev.of_node, "qcom,shared-se")) {
>>>> +        gi2c->se.shared_geni_se = true;
>>>> +        dev_dbg(&pdev->dev, "I2C is shared between subsystems\n");
>>>> +    }
>>>> +
>>>>        if (has_acpi_companion(dev))
>>>>            ACPI_COMPANION_SET(&gi2c->adap.dev, ACPI_COMPANION(dev));
>>>>    @@ -887,8 +896,10 @@ static int geni_i2c_probe(struct platform_device *pdev)
>>>>        else
>>>>            fifo_disable = readl_relaxed(gi2c->se.base + GENI_IF_DISABLE_RO) & FIFO_IF_DISABLE;
>>>>    -    if (fifo_disable) {
>>>> -        /* FIFO is disabled, so we can only use GPI DMA */
>>>> +    if (fifo_disable || gi2c->se.shared_geni_se) {
>>>> +        /* FIFO is disabled, so we can only use GPI DMA.
>>>> +         * SE can be shared in GSI mode between subsystems, each SS owns a GPII.
>>>> +         **/
>>>
>>> I don't think this change makes things clearer, I would drop it
>> Shall i revert back to previous change ? What's your suggestion ?
> 
> Yes, drop changing this comment.
Sure, Thanks for confirming !
> 
> Konrad