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

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Message-ID: <57815272-bc07-4c5e-8ae6-8bf8eaaca78f@quicinc.com>
Date: Sun, 15 Dec 2024 14:29:12 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: 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

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 ?
> 
>>   		gi2c->gpi_mode = true;
>>   		ret = setup_gpi_dma(gi2c);
>>   		if (ret) {
>> @@ -900,6 +911,12 @@ static int geni_i2c_probe(struct platform_device *pdev)
>>   		dev_dbg(dev, "Using GPI DMA mode for I2C\n");
>>   	} else {
>>   		gi2c->gpi_mode = false;
>> +
>> +		if (gi2c->se.shared_geni_se) {
>> +			dev_err(dev, "I2C sharing is not supported in non GSI mode\n");
>> +			return -EINVAL;
> 
> return dev_err_probe(dev, -EINVAL, "I2C...)
Yes, will incorporate this change in next patch. dt-binding change i am 
seeking something good writeup, then will upload V6. Thanks Konrad !
> 
> Konrad