Re: [PATCH v2 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing between two subsystems

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

Hi Neil,

On 9/9/2024 6:34 PM, neil.armstrong@linaro.org wrote:
> On 09/09/2024 11:18, Mukesh Kumar Savaliya wrote:
>> Hi Neil,
>>
>> On 9/9/2024 2:24 PM, neil.armstrong@linaro.org wrote:
>>> Hi,
>>>
>>> On 06/09/2024 21:14, Mukesh Kumar Savaliya wrote:
>>>> Add support to share I2C SE by two Subsystems 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.
>>>>
>>>> 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 for the i2c bus between two SS, do not
>>>> touch GPIO configuration during runtime suspend and only turn off the
>>>> clocks. This will allow other SS to continue to transfer the data
>>>> without any disturbance over the IO lines.
>>>
>>> This doesn't answer my question about what would be the behavior if one
>>> use uses, for example, GPI DMA, and the Linux kernel FIFO mode or SE 
>>> DMA ?
>>>
>> Shared usecase is not supported for non GSI mode (FIFO and DMA), it 
>> should be static usecase. Dynamic sharing from two clients of two 
>> subsystems is only for GSI mode. Hope this helps ?
> 
> Sure, this is why I proposed on v1 cover letter reply to add:
Sure, i will add in cover letter and code check combining with 
fifo_disable check.
> ==============><=====================================================================
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
> b/drivers/i2c/busses/i2c-qcom-geni.c
> index ee2e431601a6..a15825ea56de 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -885,7 +885,7 @@ 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) {
> +       if (gi2c->is_shared || fifo_disable) {
  Should be ANDING logically, as we need to combine both check. Shared
  usecase possible only for fifo_disable.

  if(gi2c->is_shared && fifo_disable) {
>                   /* FIFO is disabled, so we can only use GPI DMA */
>                   gi2c->gpi_mode = true;
>                   ret = setup_gpi_dma(gi2c);
> ==============><=====================================================================
> 
> Thanks,
> Neil
> 
>>> Because it seems to "fix" only the GPI DMA shared case.
>>>
>>> Neil
>>>
>>>>
>>>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@quicinc.com>
>>>> ---
>>>>   drivers/i2c/busses/i2c-qcom-geni.c | 29 ++++++++++++++++++++++-------
>>>>   1 file changed, 22 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
>>>> b/drivers/i2c/busses/i2c-qcom-geni.c
>>>> index eebb0cbb6ca4..ee2e431601a6 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>
>>>> @@ -99,6 +100,7 @@ struct geni_i2c_dev {
>>>>       struct dma_chan *rx_c;
>>>>       bool gpi_mode;
>>>>       bool abort_done;
>>>> +    bool is_shared;
>>>>   };
>>>>   struct geni_i2c_desc {
>>>> @@ -602,6 +604,7 @@ 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->is_shared;
>>>>       for (i = 0; i < num; i++) {
>>>>           gi2c->cur = &msgs[i];
>>>> @@ -612,6 +615,8 @@ 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,
>>>> @@ -631,8 +636,11 @@ static int geni_i2c_gpi_xfer(struct 
>>>> geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
>>>>           dma_async_issue_pending(gi2c->tx_c);
>>>>           time_left = wait_for_completion_timeout(&gi2c->done, 
>>>> XFER_TIMEOUT);
>>>> -        if (!time_left)
>>>> +        if (!time_left) {
>>>> +            dev_err(gi2c->se.dev, "I2C timeout gpi flags:%d 
>>>> addr:0x%x\n",
>>>> +                        gi2c->cur->flags, gi2c->cur->addr);
>>>>               gi2c->err = -ETIMEDOUT;
>>>> +        }
>>>>           if (gi2c->err) {
>>>>               ret = gi2c->err;
>>>> @@ -800,6 +808,11 @@ 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->is_shared = true;
>>>> +        dev_dbg(&pdev->dev, "Shared SE Usecase\n");
>>>> +    }
>>>> +
>>>>       if (has_acpi_companion(dev))
>>>>           ACPI_COMPANION_SET(&gi2c->adap.dev, ACPI_COMPANION(dev));
>>>> @@ -962,14 +975,16 @@ static int __maybe_unused 
>>>> geni_i2c_runtime_suspend(struct device *dev)
>>>>       struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
>>>>       disable_irq(gi2c->irq);
>>>> -    ret = geni_se_resources_off(&gi2c->se);
>>>> -    if (ret) {
>>>> -        enable_irq(gi2c->irq);
>>>> -        return ret;
>>>> -
>>>> +    if (gi2c->is_shared) {
>>>> +        geni_se_clks_off(&gi2c->se);
>>>>       } else {
>>>> -        gi2c->suspended = 1;
>>>> +        ret = geni_se_resources_off(&gi2c->se);
>>>> +        if (ret) {
>>>> +            enable_irq(gi2c->irq);
>>>> +            return ret;
>>>> +        }
>>>>       }
>>>> +    gi2c->suspended = 1;
>>>>       clk_disable_unprepare(gi2c->core_clk);
>>>
>>>
> 
>