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

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Message-ID: <cc8655ed-0021-4490-8873-519c9b5b939c@oss.qualcomm.com>
Date: Mon, 16 Dec 2024 13:10:38 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        konrad.dybcio@...aro.org, andersson@...nel.org, andi.shyti@...nel.org,
        linux-arm-msm@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        conor+dt@...nel.org, agross@...nel.org, devicetree@...r.kernel.org,
        vkoul@...nel.org, linux@...blig.org, dan.carpenter@...aro.org,
        Frank.Li@....com, konradybcio@...nel.org, bryan.odonoghue@...aro.org,
        krzk+dt@...nel.org, robh@...nel.org
Cc: quic_vdadhani@...cinc.com
Subject: Re: [PATCH v5 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing
 between two subsystems

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@...cinc.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.

Konrad