Re: [PATCH v5] vga_switcheroo: Add helper for deferred probing

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, May 21, 2016 at 03:59:16PM +0100, Lukas Wunner wrote:
> So far we've got one condition when DRM drivers need to defer probing
> on a dual GPU system and it's coded separately into each of the relevant
> drivers. As suggested by Daniel Vetter, deduplicate that code in the
> drivers and move it to a new vga_switcheroo helper. This yields better
> encapsulation of concepts and lets us add further checks in a central
> place. (The existing check pertains to pre-retina MacBook Pros and an
> additional check is expected to be needed for retinas.)
> 
> v2: This helper could eventually be used by audio clients as well,
>     so rephrase kerneldoc to refer to "client" instead of "GPU"
>     and move the single existing check in an if block specific
>     to PCI_CLASS_DISPLAY_VGA devices. Move documentation on
>     that check from kerneldoc to a comment. (Daniel Vetter)
> 
> v3: Mandate in kerneldoc that registration of client shall only
>     happen after calling this helper. (Daniel Vetter)
> 
> v4: Rebase on 412c8f7de011 ("drm/radeon: Return -EPROBE_DEFER when
>     amdkfd not loaded")
> 
> v5: Some Optimus GPUs use PCI_CLASS_DISPLAY_3D, make sure those are
>     matched as well. (Emil Velikov)
> 
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: Alex Deucher <alexander.deucher@amd.com>
> Signed-off-by: Lukas Wunner <lukas@wunner.de>
> ---
>  drivers/gpu/drm/i915/i915_drv.c       | 10 +---------
>  drivers/gpu/drm/nouveau/nouveau_drm.c | 10 +---------
>  drivers/gpu/drm/radeon/radeon_drv.c   | 10 +---------
>  drivers/gpu/vga/vga_switcheroo.c      | 34 ++++++++++++++++++++++++++++++++--
>  include/linux/vga_switcheroo.h        |  2 ++
>  5 files changed, 37 insertions(+), 29 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> index d37c0a6..20d5898 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -35,11 +35,9 @@
>  #include "i915_trace.h"
>  #include "intel_drv.h"
>  
> -#include <linux/apple-gmux.h>
>  #include <linux/console.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> -#include <linux/vgaarb.h>
>  #include <linux/vga_switcheroo.h>
>  #include <drm/drm_crtc_helper.h>
>  
> @@ -1025,13 +1023,7 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  	if (PCI_FUNC(pdev->devfn))
>  		return -ENODEV;
>  
> -	/*
> -	 * apple-gmux is needed on dual GPU MacBook Pro
> -	 * to probe the panel if we're the inactive GPU.
> -	 */
> -	if (IS_ENABLED(CONFIG_VGA_ARB) && IS_ENABLED(CONFIG_VGA_SWITCHEROO) &&
> -	    apple_gmux_present() && pdev != vga_default_device() &&
> -	    !vga_switcheroo_handler_flags())
> +	if (vga_switcheroo_client_probe_defer(pdev))
>  		return -EPROBE_DEFER;
>  
>  	return drm_get_pci_dev(pdev, ent, &driver);
> diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
> index 11f8dd9..5c4d4df 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_drm.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
> @@ -22,13 +22,11 @@
>   * Authors: Ben Skeggs
>   */
>  
> -#include <linux/apple-gmux.h>
>  #include <linux/console.h>
>  #include <linux/delay.h>
>  #include <linux/module.h>
>  #include <linux/pci.h>
>  #include <linux/pm_runtime.h>
> -#include <linux/vgaarb.h>
>  #include <linux/vga_switcheroo.h>
>  
>  #include "drmP.h"
> @@ -315,13 +313,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev,
>  	bool boot = false;
>  	int ret;
>  
> -	/*
> -	 * apple-gmux is needed on dual GPU MacBook Pro
> -	 * to probe the panel if we're the inactive GPU.
> -	 */
> -	if (IS_ENABLED(CONFIG_VGA_ARB) && IS_ENABLED(CONFIG_VGA_SWITCHEROO) &&
> -	    apple_gmux_present() && pdev != vga_default_device() &&
> -	    !vga_switcheroo_handler_flags())
> +	if (vga_switcheroo_client_probe_defer(pdev))
>  		return -EPROBE_DEFER;
>  
>  	/* remove conflicting drivers (vesafb, efifb etc) */
> diff --git a/drivers/gpu/drm/radeon/radeon_drv.c b/drivers/gpu/drm/radeon/radeon_drv.c
> index b55aa74..a455dc7 100644
> --- a/drivers/gpu/drm/radeon/radeon_drv.c
> +++ b/drivers/gpu/drm/radeon/radeon_drv.c
> @@ -34,11 +34,9 @@
>  #include "radeon_drv.h"
>  
>  #include <drm/drm_pciids.h>
> -#include <linux/apple-gmux.h>
>  #include <linux/console.h>
>  #include <linux/module.h>
>  #include <linux/pm_runtime.h>
> -#include <linux/vgaarb.h>
>  #include <linux/vga_switcheroo.h>
>  #include <drm/drm_gem.h>
>  
> @@ -340,13 +338,7 @@ static int radeon_pci_probe(struct pci_dev *pdev,
>  	if (ret == -EPROBE_DEFER)
>  		return ret;
>  
> -	/*
> -	 * apple-gmux is needed on dual GPU MacBook Pro
> -	 * to probe the panel if we're the inactive GPU.
> -	 */
> -	if (IS_ENABLED(CONFIG_VGA_ARB) && IS_ENABLED(CONFIG_VGA_SWITCHEROO) &&
> -	    apple_gmux_present() && pdev != vga_default_device() &&
> -	    !vga_switcheroo_handler_flags())
> +	if (vga_switcheroo_client_probe_defer(pdev))
>  		return -EPROBE_DEFER;
>  
>  	/* Get rid of things like offb */
> diff --git a/drivers/gpu/vga/vga_switcheroo.c b/drivers/gpu/vga/vga_switcheroo.c
> index cbd7c98..2df216b3 100644
> --- a/drivers/gpu/vga/vga_switcheroo.c
> +++ b/drivers/gpu/vga/vga_switcheroo.c
> @@ -30,6 +30,7 @@
>  
>  #define pr_fmt(fmt) "vga_switcheroo: " fmt
>  
> +#include <linux/apple-gmux.h>
>  #include <linux/console.h>
>  #include <linux/debugfs.h>
>  #include <linux/fb.h>
> @@ -308,7 +309,8 @@ static int register_client(struct pci_dev *pdev,
>   *
>   * Register vga client (GPU). Enable vga_switcheroo if another GPU and a
>   * handler have already registered. The power state of the client is assumed
> - * to be ON.
> + * to be ON. Beforehand, vga_switcheroo_client_probe_defer() shall be called
> + * to ensure that all prerequisites are met.

"shall" or "must"? It thought it's the latter ...
-Daniel
>   *
>   * Return: 0 on success, -ENOMEM on memory allocation error.
>   */
> @@ -329,7 +331,8 @@ EXPORT_SYMBOL(vga_switcheroo_register_client);
>   * @id: client identifier
>   *
>   * Register audio client (audio device on a GPU). The power state of the
> - * client is assumed to be ON.
> + * client is assumed to be ON. Beforehand, vga_switcheroo_client_probe_defer()
> + * shall be called to ensure that all prerequisites are met.
>   *
>   * Return: 0 on success, -ENOMEM on memory allocation error.
>   */
> @@ -376,6 +379,33 @@ find_active_client(struct list_head *head)
>  }
>  
>  /**
> + * vga_switcheroo_client_probe_defer() - whether to defer probing a given client
> + * @pdev: client pci device
> + *
> + * Determine whether any prerequisites are not fulfilled to probe a given
> + * client. Drivers shall invoke this early on in their ->probe callback
> + * and return %-EPROBE_DEFER if it evaluates to %true. Thou shalt not
> + * register the client ere thou hast called this.

I still think we should just smash this into the relevant _register
functions(), for safety. But I forgot the actual result of the previous
discussion ...

Imo if you can replace a bit of documentation with code to enforce an
invariant, always do it.
-Daniel

> + *
> + * Return: %true if probing should be deferred, otherwise %false.
> + */
> +bool vga_switcheroo_client_probe_defer(struct pci_dev *pdev)
> +{
> +	if ((pdev->class >> 16) == PCI_BASE_CLASS_DISPLAY) {
> +		/*
> +		 * apple-gmux is needed on pre-retina MacBook Pro
> +		 * to probe the panel if pdev is the inactive GPU.
> +		 */
> +		if (apple_gmux_present() && pdev != vga_default_device() &&
> +		    !vgasr_priv.handler_flags)
> +			return true;
> +	}
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(vga_switcheroo_client_probe_defer);
> +
> +/**
>   * vga_switcheroo_get_client_state() - obtain power state of a given client
>   * @pdev: client pci device
>   *
> diff --git a/include/linux/vga_switcheroo.h b/include/linux/vga_switcheroo.h
> index b39a5f3..960bedb 100644
> --- a/include/linux/vga_switcheroo.h
> +++ b/include/linux/vga_switcheroo.h
> @@ -165,6 +165,7 @@ int vga_switcheroo_unlock_ddc(struct pci_dev *pdev);
>  
>  int vga_switcheroo_process_delayed_switch(void);
>  
> +bool vga_switcheroo_client_probe_defer(struct pci_dev *pdev);
>  enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *dev);
>  
>  void vga_switcheroo_set_dynamic_switch(struct pci_dev *pdev, enum vga_switcheroo_state dynamic);
> @@ -188,6 +189,7 @@ static inline enum vga_switcheroo_handler_flags_t vga_switcheroo_handler_flags(v
>  static inline int vga_switcheroo_lock_ddc(struct pci_dev *pdev) { return -ENODEV; }
>  static inline int vga_switcheroo_unlock_ddc(struct pci_dev *pdev) { return -ENODEV; }
>  static inline int vga_switcheroo_process_delayed_switch(void) { return 0; }
> +static inline bool vga_switcheroo_client_probe_defer(struct pci_dev *pdev) { return false; }
>  static inline enum vga_switcheroo_state vga_switcheroo_get_client_state(struct pci_dev *dev) { return VGA_SWITCHEROO_ON; }
>  
>  static inline void vga_switcheroo_set_dynamic_switch(struct pci_dev *pdev, enum vga_switcheroo_state dynamic) {}
> -- 
> 2.8.1
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx