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Date:   Mon, 17 Aug 2020 13:15:01 +0530
From:   Vaibhav Gupta <vaibhavgupta40@gmail.com>
To:     Sam Ravnborg <sam@ravnborg.org>
Cc:     Bjorn Helgaas <helgaas@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Bjorn Helgaas <bjorn@helgaas.com>,
        Vaibhav Gupta <vaibhav.varodek@gmail.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Paul Mackerras <paulus@samba.org>,
        Russell King <linux@armlinux.org.uk>,
        Andres Salomon <dilinger@queued.net>,
        Antonino Daplas <adaplas@gmail.com>,
        dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-geode@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        Shuah Khan <skhan@linuxfoundation.org>
Subject: Re: [PATCH v2 01/12] fbdev: gxfb: use generic power management
Message-ID: <20200817074501.GC5869@gmail.com>
References: <20200810165458.GA292825@ravnborg.org>
 <20200810185723.15540-1-vaibhavgupta40@gmail.com>
 <20200810185723.15540-2-vaibhavgupta40@gmail.com>
 <20200816201601.GA1426650@ravnborg.org>
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On Sun, Aug 16, 2020 at 10:16:01PM +0200, Sam Ravnborg wrote:
> Hi Vaibhav
> 
> On Tue, Aug 11, 2020 at 12:27:12AM +0530, Vaibhav Gupta wrote:
> > Drivers should do only device-specific jobs. But in general, drivers using
> > legacy PCI PM framework for .suspend()/.resume() have to manage many PCI
> > PM-related tasks themselves which can be done by PCI Core itself. This
> > brings extra load on the driver and it directly calls PCI helper functions
> > to handle them.
> > 
> > Although the gxfb driver does not have that extra load,
> Sorry, but I am lost here.
> If this drivers does not have the extra load that you describe here then
> I really cannot see why it is relevant for this driver to describe it.
> 
> This is a seldomly touched driver - so it helps if the changelog when we
> finally touch the code is easy to parse.
> 
> > we should switch to
> > the new generic framework by updating function signatures and define a
> > "struct dev_pm_ops" variable to bind PM callbacks so that we can remove
> > the legacy .suspend & .resume bindings.
> This part matches the patch - good.
> 
> > Additionally, this helps us to
> > remove the unnecessary call to gxfb_suspend() in the event of Freeze and
> > Hibernate, as the function does nothing in their case.
> What I think you are explaining above is that the pci pm support
> will only call the suspend operation in case of suspend, so the 
> state.event == PM_EVENT_SUSPEND can be dropped in gxfb_suspend().
> 
> For reference later I would prefer that this is explained a bit
> more explicit - not that the changelog needs update anyway.
> > 
> > Signed-off-by: Vaibhav Gupta <vaibhavgupta40@gmail.com>
> Patch looks good, but please give the changelog one more go.
> I have not checked other patches - but I assume they would benefit
> from a similar clarification.
> 
> 	Sam
> 
Hello Sam

I will do the changes as suggested.

Thanks
Vaibhav Gupta
> > ---
> >  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);
> >  
> > -	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
> > +};
> > +
> >  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