Re: [Linux-kernel-mentees] [PATCH v1 01/12] fbdev: gxfb: use generic power management

[Sam Ravnborg <sam@ravnborg.org>]

Hi Vaibhav

On Wed, Aug 05, 2020 at 11:37:11PM +0530, Vaibhav Gupta wrote:
> Drivers using legacy power management .suspen()/.resume() callbacks
> have to manage PCI states and device's PM states themselves. They also
> need to take care of standard configuration registers.
> 
> Switch to generic power management framework using a single
> "struct dev_pm_ops" variable

"to take the unnecessary load from the driver."
- I do not parse the above - I cannot see what load is removed.
But the code is simpler which is fine. The drawback is that we now
always link in the suspend_gx functions but hopefultl the linker drops
them later.

> This also avoids the need for the driver to directly call most of the PCI
> helper functions and device power state control functions, as through
> the generic framework PCI Core takes care of the necessary operations,
> and drivers are required to do only device-specific jobs.
Again, I do not see what calles are removed.
A single check for the state is dropped - anything else?

> 
> Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> ---
>  drivers/video/fbdev/geode/gxfb.h       |  5 ----
>  drivers/video/fbdev/geode/gxfb_core.c  | 36 ++++++++++++++------------
>  drivers/video/fbdev/geode/suspend_gx.c |  4 ---
>  3 files changed, 20 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/video/fbdev/geode/gxfb.h b/drivers/video/fbdev/geode/gxfb.h
> index d2e9c5c8e294..792c111c21e4 100644
> --- a/drivers/video/fbdev/geode/gxfb.h
> +++ b/drivers/video/fbdev/geode/gxfb.h
> @@ -21,7 +21,6 @@ struct gxfb_par {
>  	void __iomem *dc_regs;
>  	void __iomem *vid_regs;
>  	void __iomem *gp_regs;
> -#ifdef CONFIG_PM
>  	int powered_down;
>  
>  	/* register state, for power management functionality */
> @@ -36,7 +35,6 @@ struct gxfb_par {
>  	uint64_t fp[FP_REG_COUNT];
>  
>  	uint32_t pal[DC_PAL_COUNT];
> -#endif
>  };
>  
>  unsigned int gx_frame_buffer_size(void);
> @@ -49,11 +47,8 @@ void gx_set_dclk_frequency(struct fb_info *info);
>  void gx_configure_display(struct fb_info *info);
>  int gx_blank_display(struct fb_info *info, int blank_mode);
>  
> -#ifdef CONFIG_PM
>  int gx_powerdown(struct fb_info *info);
>  int gx_powerup(struct fb_info *info);
> -#endif
> -
>  
>  /* Graphics Processor registers (table 6-23 from the data book) */
>  enum gp_registers {
> diff --git a/drivers/video/fbdev/geode/gxfb_core.c b/drivers/video/fbdev/geode/gxfb_core.c
> index d38a148d4746..44089b331f91 100644
> --- a/drivers/video/fbdev/geode/gxfb_core.c
> +++ b/drivers/video/fbdev/geode/gxfb_core.c
> @@ -322,17 +322,14 @@ static struct fb_info *gxfb_init_fbinfo(struct device *dev)
>  	return info;
>  }
>  
> -#ifdef CONFIG_PM
> -static int gxfb_suspend(struct pci_dev *pdev, pm_message_t state)
> +static int __maybe_unused gxfb_suspend(struct device *dev)
>  {
> -	struct fb_info *info = pci_get_drvdata(pdev);
> +	struct fb_info *info = dev_get_drvdata(dev);
I do not see any dev_set_drvdata() so I guess we get a NULL pointer
here which is not intended.
Adding a dev_set_data() to gxfb_probe() would do the trick.

>  
> -	if (state.event == PM_EVENT_SUSPEND) {
> -		console_lock();
> -		gx_powerdown(info);
> -		fb_set_suspend(info, 1);
> -		console_unlock();
> -	}
> +	console_lock();
> +	gx_powerdown(info);
> +	fb_set_suspend(info, 1);
> +	console_unlock();
>  
>  	/* there's no point in setting PCI states; we emulate PCI, so
>  	 * we don't end up getting power savings anyways */
> @@ -340,9 +337,9 @@ static int gxfb_suspend(struct pci_dev *pdev, pm_message_t state)
>  	return 0;
>  }
>  
> -static int gxfb_resume(struct pci_dev *pdev)
> +static int __maybe_unused gxfb_resume(struct device *dev)
>  {
> -	struct fb_info *info = pci_get_drvdata(pdev);
> +	struct fb_info *info = dev_get_drvdata(dev);
>  	int ret;
>  
>  	console_lock();
> @@ -356,7 +353,6 @@ static int gxfb_resume(struct pci_dev *pdev)
>  	console_unlock();
>  	return 0;
>  }
> -#endif
>  
>  static int gxfb_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
> @@ -467,15 +463,23 @@ static const struct pci_device_id gxfb_id_table[] = {
>  
>  MODULE_DEVICE_TABLE(pci, gxfb_id_table);
>  
> +static const struct dev_pm_ops gxfb_pm_ops = {
> +#ifdef CONFIG_PM_SLEEP
> +	.suspend	= gxfb_suspend,
> +	.resume		= gxfb_resume,
> +	.freeze		= NULL,
> +	.thaw		= gxfb_resume,
> +	.poweroff	= NULL,
> +	.restore	= gxfb_resume,
> +#endif
> +};
Can we use SET_SYSTEM_SLEEP_PM_OPS here?
.freeze will be assigned gxfb_suspend, but gxfb_suspend will anyway be
called as far as I read the code.
Likewise for poweroff.

	Sam

> +
>  static struct pci_driver gxfb_driver = {
>  	.name		= "gxfb",
>  	.id_table	= gxfb_id_table,
>  	.probe		= gxfb_probe,
>  	.remove		= gxfb_remove,
> -#ifdef CONFIG_PM
> -	.suspend	= gxfb_suspend,
> -	.resume		= gxfb_resume,
> -#endif
> +	.driver.pm	= &gxfb_pm_ops,
>  };
>  
>  #ifndef MODULE
> diff --git a/drivers/video/fbdev/geode/suspend_gx.c b/drivers/video/fbdev/geode/suspend_gx.c
> index 1110a527c35c..8c49d4e98772 100644
> --- a/drivers/video/fbdev/geode/suspend_gx.c
> +++ b/drivers/video/fbdev/geode/suspend_gx.c
> @@ -11,8 +11,6 @@
>  
>  #include "gxfb.h"
>  
> -#ifdef CONFIG_PM
> -
>  static void gx_save_regs(struct gxfb_par *par)
>  {
>  	int i;
> @@ -259,5 +257,3 @@ int gx_powerup(struct fb_info *info)
>  	par->powered_down  = 0;
>  	return 0;
>  }
> -
> -#endif
> -- 
> 2.27.0
> 
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