Re: [Linux-kernel-mentees] [PATCH v1] i2c: eg20t: use generic power management

[Bjorn Helgaas <helgaas@kernel.org>]

[+cc Tomoya, Linus, Qi, Ben from e9bc8fa5df1c]

On Mon, Jul 20, 2020 at 07:30:32PM +0530, Vaibhav Gupta wrote:
> Drivers using legacy PM have to manage PCI states and device's PM states
> themselves. They also need to take care of configuration registers.
> 
> With improved and powerful support of generic PM, PCI Core takes care of
> above mentioned, device-independent, jobs.
> 
> This driver makes use of PCI helper functions like
> pci_save/restore_state(), pci_enable/disable_device(),
> pci_enable_wake() and pci_set_power_state() to do required operations. In
> generic mode, they are no longer needed.
> 
> Change function parameter in both .suspend() and .resume() to
> "struct device*" type. Use to_pci_dev() and dev_get_drvdata() to get
> "struct pci_dev*" variable and drv data.
> 
> Compile-tested only.
> 
> Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> ---
>  drivers/i2c/busses/i2c-eg20t.c | 39 ++++++++--------------------------
>  1 file changed, 9 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-eg20t.c b/drivers/i2c/busses/i2c-eg20t.c
> index 73f139690e4e..c0ddc4cc2ce7 100644
> --- a/drivers/i2c/busses/i2c-eg20t.c
> +++ b/drivers/i2c/busses/i2c-eg20t.c
> @@ -846,11 +846,10 @@ static void pch_i2c_remove(struct pci_dev *pdev)
>  	kfree(adap_info);
>  }
>  
> -#ifdef CONFIG_PM
> -static int pch_i2c_suspend(struct pci_dev *pdev, pm_message_t state)
> +static int __maybe_unused pch_i2c_suspend(struct device *dev)
>  {
> -	int ret;
>  	int i;
> +	struct pci_dev *pdev = to_pci_dev(dev);
>  	struct adapter_info *adap_info = pci_get_drvdata(pdev);

Why don't you use "adap_info = dev_get_drvdata(dev)" as you did below,
so you don't need to_pci_dev()?

>  	void __iomem *p = adap_info->pch_data[0].pch_base_address;
>  
> @@ -872,34 +871,17 @@ static int pch_i2c_suspend(struct pci_dev *pdev, pm_message_t state)
>  		ioread32(p + PCH_I2CSR), ioread32(p + PCH_I2CBUFSTA),
>  		ioread32(p + PCH_I2CESRSTA));
>  
> -	ret = pci_save_state(pdev);
> -
> -	if (ret) {
> -		pch_pci_err(pdev, "pci_save_state\n");
> -		return ret;
> -	}
> -
> -	pci_enable_wake(pdev, PCI_D3hot, 0);
> -	pci_disable_device(pdev);
> -	pci_set_power_state(pdev, pci_choose_state(pdev, state));
> +	device_wakeup_disable(dev);
>  
>  	return 0;
>  }
>  
> -static int pch_i2c_resume(struct pci_dev *pdev)
> +static int __maybe_unused pch_i2c_resume(struct device *dev)
>  {
>  	int i;
> -	struct adapter_info *adap_info = pci_get_drvdata(pdev);
> -
> -	pci_set_power_state(pdev, PCI_D0);
> -	pci_restore_state(pdev);
> +	struct adapter_info *adap_info = dev_get_drvdata(dev);
>  
> -	if (pci_enable_device(pdev) < 0) {
> -		pch_pci_err(pdev, "pch_i2c_resume:pci_enable_device FAILED\n");
> -		return -EIO;
> -	}
> -
> -	pci_enable_wake(pdev, PCI_D3hot, 0);
> +	device_wakeup_disable(dev);

It *looks* wrong to disable wakeup in both suspend and resume.  I
think the usual pattern is to enable wakeup in suspend and disable it
in resume.

But it looks like it's been that way since the driver was added by
e9bc8fa5df1c ("i2c-eg20t: add driver for Intel EG20T").

If the device doesn't support wakeup, I would not expect the driver to
mention wakeup at all.

In any case, I think it's the right thing for *this* patch to preserve
the previous wakeup behavior.  Maybe we want a follow-up patch to just
remove both device_wakeup_disable() calls?

>  	for (i = 0; i < adap_info->ch_num; i++)
>  		pch_i2c_init(&adap_info->pch_data[i]);
> @@ -908,18 +890,15 @@ static int pch_i2c_resume(struct pci_dev *pdev)
>  
>  	return 0;
>  }
> -#else
> -#define pch_i2c_suspend NULL
> -#define pch_i2c_resume NULL
> -#endif
> +
> +static SIMPLE_DEV_PM_OPS(pch_i2c_pm_ops, pch_i2c_suspend, pch_i2c_resume);
>  
>  static struct pci_driver pch_pcidriver = {
>  	.name = KBUILD_MODNAME,
>  	.id_table = pch_pcidev_id,
>  	.probe = pch_i2c_probe,
>  	.remove = pch_i2c_remove,
> -	.suspend = pch_i2c_suspend,
> -	.resume = pch_i2c_resume
> +	.driver.pm = &pch_i2c_pm_ops,
>  };
>  
>  module_pci_driver(pch_pcidriver);
> -- 
> 2.27.0
> 
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