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Date:   Mon, 17 May 2021 12:02:50 +0530
From:   rojay@codeaurora.org
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     wsa@kernel.org, dianders@chromium.org,
        saiprakash.ranjan@codeaurora.org, gregkh@linuxfoundation.org,
        mka@chromium.org, skananth@codeaurora.org,
        msavaliy@qti.qualcomm.com, skakit@codeaurora.org,
        rnayak@codeaurora.org, agross@kernel.org,
        bjorn.andersson@linaro.org, linux-arm-msm@vger.kernel.org,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        sumit.semwal@linaro.org, linux-media@vger.kernel.org
Subject: Re: [PATCH V10] i2c: i2c-qcom-geni: Add shutdown callback for i2c
In-Reply-To: <CAE-0n52D-K1T0QgxA-S7BXxE3Qk807F9edNyR+2RL4YxRyigMg@mail.gmail.com>
References: <20210512082220.7137-1-rojay@codeaurora.org>
 <CAE-0n52D-K1T0QgxA-S7BXxE3Qk807F9edNyR+2RL4YxRyigMg@mail.gmail.com>
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Hi Stephen,

On 2021-05-13 00:27, Stephen Boyd wrote:
> Quoting Roja Rani Yarubandi (2021-05-12 01:22:20)
>> If the hardware is still accessing memory after SMMU translation
>> is disabled (as part of smmu shutdown callback), then the
>> IOVAs (I/O virtual address) which it was using will go on the bus
>> as the physical addresses which will result in unknown crashes
>> like NoC/interconnect errors.
>> 
>> So, implement shutdown callback for i2c driver to suspend the bus
>> during system "reboot" or "shutdown".
>> 
>> Fixes: 37692de5d523 ("i2c: i2c-qcom-geni: Add bus driver for the 
>> Qualcomm GENI I2C controller")
>> Signed-off-by: Roja Rani Yarubandi <rojay@codeaurora.org>
>> ---
>> Changes in V2:
>>  - As per Stephen's comments added seperate function for stop 
>> transfer,
>>    fixed minor nitpicks.
>>  - As per Stephen's comments, changed commit text.
>> 
>> Changes in V3:
>>  - As per Stephen's comments, squashed patch 1 into patch 2, added 
>> Fixes tag.
>>  - As per Akash's comments, included FIFO case in stop_xfer, fixed 
>> minor nitpicks.
>> 
>> Changes in V4:
>>  - As per Stephen's comments cleaned up geni_i2c_stop_xfer function,
>>    added dma_buf in geni_i2c_dev struct to call 
>> i2c_put_dma_safe_msg_buf()
>>    from other functions, removed "iova" check in 
>> geni_se_rx_dma_unprep()
>>    and geni_se_tx_dma_unprep() functions.
>>  - Added two helper functions geni_i2c_rx_one_msg_done() and
>>    geni_i2c_tx_one_msg_done() to unwrap the things after rx/tx 
>> FIFO/DMA
>>    transfers, so that the same can be used in geni_i2c_stop_xfer() 
>> function
>>    during shutdown callback. Updated commit text accordingly.
>>  - Checking whether it is tx/rx transfer using I2C_M_RD which is valid 
>> for both
>>    FIFO and DMA cases, so dropped DMA_RX_ACTIVE and DMA_TX_ACTIVE bit 
>> checking
>> 
>> Changes in V5:
>>  - As per Stephen's comments, added spin_lock_irqsave & 
>> spin_unlock_irqsave in
>>    geni_i2c_stop_xfer() function.
>> 
>> Changes in V6:
>>  - As per Stephen's comments, taken care of unsafe lock order in
>>    geni_i2c_stop_xfer().
>>  - Moved spin_lock/unlock to geni_i2c_rx_msg_cleanup() and
>>    geni_i2c_tx_msg_cleanup() functions.
>> 
>> Changes in V7:
>>  - No changes
>> 
>> Changes in V8:
>>  - As per Wolfram Sang comment, removed goto and modified 
>> geni_i2c_stop_xfer()
>>    accordingly.
>> 
>> Changes in V9:
>>  - Fixed possbile race by protecting gi2c->cur and calling 
>> geni_i2c_abort_xfer()
>>    with adding another parameter to differentiate from which sequence 
>> is the
>>    geni_i2c_abort_xfer() called and handle the spin_lock/spin_unlock 
>> accordingly
>>    inside geni_i2c_abort_xfer(). For this added two macros ABORT_XFER 
>> and
>>    STOP_AND_ABORT_XFER.
>>  - Added a bool variable "stop_xfer" in geni_i2c_dev struct, used to 
>> put stop
>>    to upcoming geni_i2c_rx_one_msg() and geni_i2c_tx_one_msg() calls 
>> once we
>>    recieve the shutdown call.
>>  - Added gi2c->cur == NULL check in geni_i2c_irq() to not to process 
>> the irq
>>    even if any transfer is queued and shutdown to HW received.
>> 
>> Changes in V10:
>>  - As per Stephen's comments, removed ongoing transfers flush and only
>>    suspending i2c bus in shutdown callback.
>>  - Also removed all other changes which have been made for ongoing 
>> transfers
>>    flush, handling race issues etc., during shutdown callback.
>>  - Updated commit text accordingly.
>> 
>>  drivers/i2c/busses/i2c-qcom-geni.c | 9 +++++++++
>>  1 file changed, 9 insertions(+)
>> 
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c 
>> b/drivers/i2c/busses/i2c-qcom-geni.c
>> index 214b4c913a13..277ab7e7dd51 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -650,6 +650,14 @@ static int geni_i2c_remove(struct platform_device 
>> *pdev)
>>         return 0;
>>  }
>> 
>> +static void geni_i2c_shutdown(struct platform_device *pdev)
>> +{
>> +       struct geni_i2c_dev *gi2c = platform_get_drvdata(pdev);
>> +
>> +       if (!pm_runtime_status_suspended(gi2c->se.dev))
>> +               pm_runtime_set_suspended(gi2c->se.dev);
> 
> What was wrong with my suggested approach of telling i2c core that the
> bus is suspended? This looks to do a bunch of work right before we're
> shutting down, when it would be simpler to just mark the bus as
> suspended and have it block future transactions and spit out a warning.
> 

Sorry, I have overlooked your previous change. I will do that.

> I do see that we should be marking it suspended/resumed during runtime
> suspend/resume. I'm also confused if during system wide suspend/resume
> we actually do anything in this driver. Is runtime suspend called for
> system wide suspend?
> 

In this geni i2c driver, runtime suspend will be called during system 
suspend
if the device is NOT already suspended.

> ----8<----
> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c
> b/drivers/i2c/busses/i2c-qcom-geni.c
> index 214b4c913a13..ca12d348336b 100644
> --- a/drivers/i2c/busses/i2c-qcom-geni.c
> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
> @@ -656,6 +656,7 @@ static int __maybe_unused
> geni_i2c_runtime_suspend(struct device *dev)
>  	struct geni_i2c_dev *gi2c = dev_get_drvdata(dev);
> 
>  	disable_irq(gi2c->irq);
> +	i2c_mark_adapter_suspended(&gi2c->adap);
>  	ret = geni_se_resources_off(&gi2c->se);
>  	if (ret) {
>  		enable_irq(gi2c->irq);
> @@ -682,6 +683,7 @@ static int __maybe_unused
> geni_i2c_runtime_resume(struct device *dev)
>  		return ret;
> 
>  	enable_irq(gi2c->irq);
> +	i2c_mark_adapter_resumed(&gi2c->adap);
>  	gi2c->suspended = 0;
>  	return 0;
>  }

Now, I have made the changes, calling i2c_mark_adapter_suspended() in
shutdown() and i2c_mark_adapter_suspended()/_resumed() from runtime
suspend/resume also and validated the changes. I have also picked
your patch [1] for this validation.

During the device boot up I am seeing multiple traces shown below.
Are these expected now and needs to be fixed from rt5682/respective
client driver?

Trace1:
[   11.709477] i2c i2c-9: Transfer while suspended
[   11.905595] Call trace:
[   11.908124]  __i2c_transfer+0xb8/0x38c
[   11.911984]  i2c_transfer+0xa0/0xf4
[   11.915569]  i2c_transfer_buffer_flags+0x68/0x9c
[   11.920314]  regmap_i2c_write+0x34/0x64
[   11.924255]  _regmap_raw_write_impl+0x4e8/0x7bc
[   11.928911]  _regmap_bus_raw_write+0x70/0x8c
[   11.933301]  _regmap_write+0x100/0x150
[   11.937152]  regmap_write+0x54/0x78
[   11.940744]  soc_component_write_no_lock+0x34/0xa8
[   11.945666]  snd_soc_component_write+0x3c/0x5c
[   11.950242]  rt5682_set_component_pll+0x1e4/0x2b4 [snd_soc_rt5682]
[   11.956588]  snd_soc_component_set_pll+0x50/0xa8
[   11.961328]  snd_soc_dai_set_pll+0x74/0xc8
[   11.965542]  sc7180_snd_startup+0x9c/0x120 [snd_soc_sc7180]
[   11.971262]  snd_soc_link_startup+0x34/0x88
[   11.975557]  soc_pcm_open+0x100/0x538
[   11.979323]  snd_pcm_open_substream+0x530/0x704
[   11.983980]  snd_pcm_open+0xc8/0x210
[   11.987653]  snd_pcm_playback_open+0x50/0x80
[   11.992049]  snd_open+0x120/0x150
[   11.995462]  chrdev_open+0xb8/0x1a4
[   11.999056]  do_dentry_open+0x238/0x358
[   12.003001]  vfs_open+0x34/0x40
[   12.006235]  path_openat+0x9e8/0xd60
[   12.009913]  do_filp_open+0x90/0x10c
[   12.013587]  do_sys_open+0x148/0x314
[   12.017260]  __arm64_compat_sys_openat+0x28/0x34
[   12.022009]  el0_svc_common+0xa4/0x16c
[   12.025860]  el0_svc_compat_handler+0x2c/0x40
[   12.030337]  el0_svc_compat+0x8/0x10
[   12.034018] ---[ end trace 745ead557fcbb5dc ]---
[   12.040151] rt5682 9-001a: ASoC: error at soc_component_write_no_lock 
on rt5682.9-001a: -108
[   12.049055] rt5682 9-001a: ASoC: error at soc_component_write_no_lock 
on rt5682.9-001a: -108
[   12.057742] rt5682 9-001a: ASoC: error at 
snd_soc_component_update_bits on rt5682.9-001a: -108

Trace2:
[    3.515390] i2c i2c-2: Transfer while suspended
[    3.606749] Call trace:
[    3.606751]  __i2c_transfer+0xb8/0x38c
[    3.606752]  i2c_transfer+0xa0/0xf4
[    3.606754]  i2c_transfer_buffer_flags+0x68/0x9c
[    3.639599] hub 2-1.4:1.0: USB hub found
[    3.644375]  regmap_i2c_write+0x34/0x64
[    3.644376]  _regmap_raw_write_impl+0x4e8/0x7bc
[    3.644378]  _regmap_bus_raw_write+0x70/0x8c
[    3.644379]  _regmap_write+0x100/0x150
[    3.644381]  regmap_write+0x54/0x78
[    3.644383]  ti_sn_aux_transfer+0x90/0x244
[    3.650695] hub 2-1.4:1.0: 4 ports detected
[    3.655288]  drm_dp_dpcd_access+0x8c/0x11c
[    3.655289]  drm_dp_dpcd_read+0x64/0x10c
[    3.655290]  ti_sn_bridge_enable+0x5c/0x824
[    3.655292]  drm_atomic_bridge_chain_enable+0x78/0xa0
[    3.655294]  drm_atomic_helper_commit_modeset_enables+0x198/0x238
[    3.655295]  msm_atomic_commit_tail+0x324/0x714
[    3.655297]  commit_tail+0xa4/0x108
[    3.664985] usb 1-1.4: new high-speed USB device number 4 using 
xhci-hcd
[    3.666204]  drm_atomic_helper_commit+0xf4/0xfc
[    3.666205]  drm_atomic_commit+0x50/0x5c
[    3.666206]  drm_atomic_helper_set_config+0x64/0x98
[    3.666208]  drm_mode_setcrtc+0x26c/0x590
[    3.666209]  drm_ioctl_kernel+0x9c/0x114
[    3.701074] hub 2-1.4:1.0: USB hub found
[    3.703347]  drm_ioctl+0x288/0x420
[    3.703349]  drm_compat_ioctl+0xd0/0xe0
[    3.703351]  __arm64_compat_sys_ioctl+0x100/0x2108
[    3.703354]  el0_svc_common+0xa4/0x16c
[    3.708499] hub 2-1.4:1.0: 4 ports detected
[    3.711588]  el0_svc_compat_handler+0x2c/0x40
[    3.711590]  el0_svc_compat+0x8/0x10
[    3.711591] ---[ end trace 745ead557fcbb5db ]---
[    3.772120] usb 1-1.4: New USB device found, idVendor=0bda, 
idProduct=5411, bcdDevice= 1.04
[    3.794990] ti_sn65dsi86 2-002d: [drm:ti_sn_bridge_enable] *ERROR* 
Can't read lane count (-108); assuming 4

[1] 
https://lore.kernel.org/r/20210508075151.1626903-2-swboyd@chromium.org

Thanks,
Roja