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

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Date:   Wed, 5 Aug 2020 11:16:22 +0200
From:   Wolfram Sang <wsa@...nel.org>
To:     Vaibhav Gupta <vaibhavgupta40@...il.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Bjorn Helgaas <bjorn@...gaas.com>,
        Vaibhav Gupta <vaibhav.varodek@...il.com>,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v1] i2c: eg20t: use generic power management

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@...il.com>

Looks reasonable, but to make sure I'd like a test from someone with HW
or an ack from someone more experienced with PCI details.

> ---
>  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);
>  	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);
>  
>  	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);

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