[Intel-gfx] [RFC] i915: make the probe asynchronous

[Takashi Iwai]

On Wed, 20 Jun 2018 08:25:23 +0200,
Feng Tang wrote:
> 
> Hi Jani/Chris/Takashi, 
> 
> On Wed, Jun 06, 2018 at 11:21:43AM +0300, Jani Nikula wrote:
> > >> 
> > >> http://patchwork.freedesktop.org/patch/msgid/20180323083048.13327-1-chris@chris-wilson.co.uk
> > >
> > > IIUC, you are waiting for the HDA audio driver to first handle the
> > > i915 sync probel case?
> > 
> > I wouldn't hold my breath waiting. If you want to do i915 async probe,
> > you'll probably have to figure hda out as well.
> 
> I made the following patch based on 4.18-rc1, and tested on my machine,
> which basically works fine with Async probe taking effect (I tried
> builtin and modules way).
> 
> Please review this initial version, and I'll separate to clean patches
> if you think it's OK. thanks!

When you call an i915 function from HD-audio driver, you made already
a hard dependency.  This is exactly what we want to avoid.


thanks,

Takashi

> 
> - Feng
> 
> 
> ------
> diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> index 4364922..16a59ae 100644
> --- a/drivers/gpu/drm/i915/i915_pci.c
> +++ b/drivers/gpu/drm/i915/i915_pci.c
> @@ -671,6 +671,21 @@ static const struct pci_device_id pciidlist[] = {
>  };
>  MODULE_DEVICE_TABLE(pci, pciidlist);
>  
> +static struct completion i915_probe_done;
> +
> +int wait_i915_probe_done(int timeout)
> +{
> +	int ret;
> +
> +	ret = wait_for_completion_interruptible_timeout(&i915_probe_done, timeout);
> +	if (ret <= 0)
> +		return -ENODEV;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(wait_i915_probe_done);
> +
> +
>  static void i915_pci_remove(struct pci_dev *pdev)
>  {
>  	struct drm_device *dev = pci_get_drvdata(pdev);
> @@ -717,6 +732,7 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  		return err > 0 ? -ENOTTY : err;
>  	}
>  
> +	complete_all(&i915_probe_done);
>  	return 0;
>  }
>  
> @@ -726,6 +742,7 @@ static struct pci_driver i915_pci_driver = {
>  	.probe = i915_pci_probe,
>  	.remove = i915_pci_remove,
>  	.driver.pm = &i915_pm_ops,
> +	.driver.probe_type = PROBE_PREFER_ASYNCHRONOUS,
>  };
>  
>  static int __init i915_init(void)
> @@ -755,6 +772,8 @@ static int __init i915_init(void)
>  		return 0;
>  	}
>  
> +	init_completion(&i915_probe_done);
> +
>  	return pci_register_driver(&i915_pci_driver);
>  }
>  
> diff --git a/include/drm/i915_drm.h b/include/drm/i915_drm.h
> index c9e5a66..adae172 100644
> --- a/include/drm/i915_drm.h
> +++ b/include/drm/i915_drm.h
> @@ -36,6 +36,12 @@ extern bool i915_gpu_lower(void);
>  extern bool i915_gpu_busy(void);
>  extern bool i915_gpu_turbo_disable(void);
>  
> +/*
> + * For use by HDA driver for now
> + * Return 0 on i915 probe is done, and -ENODEV on error
> + */
> +extern int wait_i915_probe_done(int timeout);
> +
>  /* Exported from arch/x86/kernel/early-quirks.c */
>  extern struct resource intel_graphics_stolen_res;
>  
> diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
> index cbe818e..48e5039 100644
> --- a/sound/hda/hdac_i915.c
> +++ b/sound/hda/hdac_i915.c
> @@ -17,6 +17,7 @@
>  #include <linux/pci.h>
>  #include <linux/component.h>
>  #include <drm/i915_component.h>
> +#include <drm/i915_drm.h>
>  #include <sound/core.h>
>  #include <sound/hdaudio.h>
>  #include <sound/hda_i915.h>
> @@ -357,6 +358,7 @@ static bool i915_gfx_present(void)
>   *
>   * Returns zero for success or a negative error code.
>   */
> +#define HDAC_WAIT_I915_LOAD_MS	3000
>  int snd_hdac_i915_init(struct hdac_bus *bus)
>  {
>  	struct component_match *match = NULL;
> @@ -386,7 +388,11 @@ int snd_hdac_i915_init(struct hdac_bus *bus)
>  	 * Atm, we don't support deferring the component binding, so make sure
>  	 * i915 is loaded and that the binding successfully completes.
>  	 */
> -	request_module("i915");
> +	ret = wait_i915_probe_done(HDAC_WAIT_I915_LOAD_MS);
> +	if (ret) {
> +		dev_info(dev, "failed to wait for i915 probe done\n");
> +		goto out_master_del;
> +	}
>  
>  	if (!acomp->ops) {
>  		ret = -ENODEV;
>