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

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Message-ID: <f57d3f3e-1cc1-48c5-9034-d8b40ad0fb6d@quicinc.com>
Date: Tue, 10 Sep 2024 14:42:23 +0530
From: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.com>
To: <neil.armstrong@...aro.org>, <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>
CC: <quic_vdadhani@...cinc.com>
Subject: Re: [PATCH v2 4/4] i2c: i2c-qcom-geni: Enable i2c controller sharing
 between two subsystems

Hi Neil,

On 9/9/2024 2:24 PM, neil.armstrong@...aro.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 ?
> 
> Because it seems to "fix" only the GPI DMA shared case.
> 
This shared usecase is possible only GPI DMA mode, not for the FIFO OR 
SE DMA mode. Let me add conditional mask with GPI DMA mode only. Hope 
that would clarify ?
> Neil
> 
>>
>> Signed-off-by: Mukesh Kumar Savaliya <quic_msavaliy@...cinc.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);
> 
>