Messages in this thread | | | Subject | Re: [PATCH V1] i2c: busses: tegra: Add suspend-resume support | From | Bitan Biswas <> | Date | Thu, 6 Jun 2019 06:55:44 -0700 |
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On 6/6/19 4:52 AM, Dmitry Osipenko wrote: > 06.06.2019 8:43, Bitan Biswas пишет: >> >> >> On 5/31/19 5:43 AM, Dmitry Osipenko wrote: >>> 31.05.2019 11:50, Bitan Biswas пишет: >>>> >>>> >>>> On 5/30/19 4:27 AM, Dmitry Osipenko wrote: >>>>> 30.05.2019 8:55, Bitan Biswas пишет: >>>>>> Post suspend I2C registers have power on reset values. Before any >>>>>> transfer initialize I2C registers to prevent I2C transfer timeout >>>>>> and implement suspend and resume callbacks needed. Fix below errors >>>>>> post suspend: >>>>>> >>>>>> 1) Tegra I2C transfer timeout during jetson tx2 resume: >>>>>> >>>>>> [ 27.520613] pca953x 1-0074: calling pca953x_resume+0x0/0x1b0 @ >>>>>> 2939, parent: i2c-1 >>>>>> [ 27.633623] tegra-i2c 3160000.i2c: i2c transfer timed out >>>>>> [ 27.639162] pca953x 1-0074: Unable to sync registers 0x3-0x5. -110 >>>>>> [ 27.645336] pca953x 1-0074: Failed to sync GPIO dir registers: -110 >>>>>> [ 27.651596] PM: dpm_run_callback(): pca953x_resume+0x0/0x1b0 >>>>>> returns -110 >>>>>> [ 27.658375] pca953x 1-0074: pca953x_resume+0x0/0x1b0 returned -110 >>>>>> after 127152 usecs >>>>>> [ 27.666194] PM: Device 1-0074 failed to resume: error -110 >>>>>> >>>>>> 2) Tegra I2C transfer timeout error on jetson Xavier post resume. >>>>>> >>>>>> Signed-off-by: Bitan Biswas <bbiswas@nvidia.com> >>>>>> --- >>>>>> drivers/i2c/busses/i2c-tegra.c | 24 ++++++++++++++++++++++++ >>>>>> 1 file changed, 24 insertions(+) >>>>>> >>>>>> diff --git a/drivers/i2c/busses/i2c-tegra.c >>>>>> b/drivers/i2c/busses/i2c-tegra.c >>>>>> index ebaa78d..f6a377f 100644 >>>>>> --- a/drivers/i2c/busses/i2c-tegra.c >>>>>> +++ b/drivers/i2c/busses/i2c-tegra.c >>>>>> @@ -1687,9 +1687,33 @@ static int tegra_i2c_remove(struct >>>>>> platform_device *pdev) >>>>>> } >>>>>> #ifdef CONFIG_PM_SLEEP >>>>>> +static int tegra_i2c_suspend(struct device *dev) >>>>>> +{ >>>>>> + struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev); >>>>>> + >>>>>> + i2c_mark_adapter_suspended(&i2c_dev->adapter); >>>>>> + >>>>>> + return 0; >>>>>> +} >>>>>> + >>>>>> +static int tegra_i2c_resume(struct device *dev) >>>>>> +{ >>>>>> + struct tegra_i2c_dev *i2c_dev = dev_get_drvdata(dev); >>>>>> + int ret; >>>>>> + >>>>>> + i2c_lock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER); >>>>>> + ret = tegra_i2c_init(i2c_dev, false); >>>>>> + i2c_unlock_bus(&i2c_dev->adapter, I2C_LOCK_ROOT_ADAPTER); >>>>> >>>>> Why the locking is needed here? >>>> >>>> async resume could result in stress test issues if some client accesses >>>> the i2c instance. This ensures the i2c instance is locked till the >>>> initialization is complete. >>> >>> 1) This doesn't make much sense.. if client could access I2C during of >>> tegra_i2c_init execution, then what stops it to perform the access >>> before the lock is taken? >> Client resumes will start after I2C instance resume because of driver >> dependency. Since lock is the first call in i2c-tegra I believe I2C >> calls of client will not start. > > You're incorrectly assuming that client can start resuming in the middle > of the controller's resume process. I2C client's resume won't start > until tegra_i2c_resume() is finished completely. That is because child > drivers are resumed only after theirs parent is ready and this is > guaranteed by the drivers core. > Agreed.
-regards, Bitan
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