Re: [Intel-gfx] [PATCH v2] fbdev/efifb: Release PCI device's runtime PM ref during FB destroy

[Imre Deak <imre.deak@intel.com>]

Hi Kai-Heng, Alex,

could you add your ack if the fix looks ok and you're ok if I push it to
the i915 tree?

Thanks,
Imre

On Mon, Aug 09, 2021 at 04:31:46PM +0300, Imre Deak wrote:
> Atm the EFI FB platform driver gets a runtime PM reference for the
> associated GFX PCI device during probing the EFI FB platform device and
> releases it only when the platform device gets unbound.
> 
> When fbcon switches to the FB provided by the PCI device's driver (for
> instance i915/drmfb), the EFI FB will get only unregistered without the
> EFI FB platform device getting unbound, keeping the runtime PM reference
> acquired during the platform device probing. This reference will prevent
> the PCI driver from runtime suspending the device.
> 
> Fix this by releasing the RPM reference from the EFI FB's destroy hook,
> called when the FB gets unregistered.
> 
> While at it assert that pm_runtime_get_sync() didn't fail.
> 
> v2:
> - Move pm_runtime_get_sync() before register_framebuffer() to avoid its
>   race wrt. efifb_destroy()->pm_runtime_put(). (Daniel)
> - Assert that pm_runtime_get_sync() didn't fail.
> - Clarify commit message wrt. platform/PCI device/driver and driver
>   removal vs. device unbinding.
> 
> Fixes: a6c0fd3d5a8b ("efifb: Ensure graphics device for efifb stays at PCI D0")
> Cc: Kai-Heng Feng <kai.heng.feng@canonical.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v1)
> Signed-off-by: Imre Deak <imre.deak@intel.com>
> ---
>  drivers/video/fbdev/efifb.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 8ea8f079cde26..edca3703b9640 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -47,6 +47,8 @@ static bool use_bgrt = true;
>  static bool request_mem_succeeded = false;
>  static u64 mem_flags = EFI_MEMORY_WC | EFI_MEMORY_UC;
>  
> +static struct pci_dev *efifb_pci_dev;	/* dev with BAR covering the efifb */
> +
>  static struct fb_var_screeninfo efifb_defined = {
>  	.activate		= FB_ACTIVATE_NOW,
>  	.height			= -1,
> @@ -243,6 +245,9 @@ static inline void efifb_show_boot_graphics(struct fb_info *info) {}
>  
>  static void efifb_destroy(struct fb_info *info)
>  {
> +	if (efifb_pci_dev)
> +		pm_runtime_put(&efifb_pci_dev->dev);
> +
>  	if (info->screen_base) {
>  		if (mem_flags & (EFI_MEMORY_UC | EFI_MEMORY_WC))
>  			iounmap(info->screen_base);
> @@ -333,7 +338,6 @@ ATTRIBUTE_GROUPS(efifb);
>  
>  static bool pci_dev_disabled;	/* FB base matches BAR of a disabled device */
>  
> -static struct pci_dev *efifb_pci_dev;	/* dev with BAR covering the efifb */
>  static struct resource *bar_resource;
>  static u64 bar_offset;
>  
> @@ -569,17 +573,22 @@ static int efifb_probe(struct platform_device *dev)
>  		pr_err("efifb: cannot allocate colormap\n");
>  		goto err_groups;
>  	}
> +
> +	if (efifb_pci_dev)
> +		WARN_ON(pm_runtime_get_sync(&efifb_pci_dev->dev) < 0);
> +
>  	err = register_framebuffer(info);
>  	if (err < 0) {
>  		pr_err("efifb: cannot register framebuffer\n");
> -		goto err_fb_dealoc;
> +		goto err_put_rpm_ref;
>  	}
>  	fb_info(info, "%s frame buffer device\n", info->fix.id);
> -	if (efifb_pci_dev)
> -		pm_runtime_get_sync(&efifb_pci_dev->dev);
>  	return 0;
>  
> -err_fb_dealoc:
> +err_put_rpm_ref:
> +	if (efifb_pci_dev)
> +		pm_runtime_put(&efifb_pci_dev->dev);
> +
>  	fb_dealloc_cmap(&info->cmap);
>  err_groups:
>  	sysfs_remove_groups(&dev->dev.kobj, efifb_groups);
> @@ -603,8 +612,6 @@ static int efifb_remove(struct platform_device *pdev)
>  	unregister_framebuffer(info);
>  	sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
>  	framebuffer_release(info);
> -	if (efifb_pci_dev)
> -		pm_runtime_put(&efifb_pci_dev->dev);
>  
>  	return 0;
>  }
> -- 
> 2.27.0
>