Re: [Intel-gfx] [PATCH v5 7/7] drm/i915: Implement fbdev emulation as in-kernel client

["Hogander, Jouni" <jouni.hogander@intel.com>]

Hi Thomas, couple of minor comments and a question below.

On Wed, 2023-09-27 at 12:26 +0200, Thomas Zimmermann wrote:
> Replace all code that initializes or releases fbdev emulation
> throughout the driver. Instead initialize the fbdev client by a
> single call to i915_fbdev_setup() after i915 has registered its

intel_fbdev_setup

> DRM device. Just like similar code in other drivers, i915 fbdev
> emulation now acts as a regular DRM client.
> 
> The fbdev client setup consists of the initial preparation and the
> hot-plugging of the display. The latter creates the fbdev device
> and sets up the fbdev framebuffer. The setup performs display
> hot-plugging once. If no display can be detected, DRM probe helpers
> re-run the detection on each hotplug event.
> 
> A call to drm_dev_unregister() releases the client automatically.
> No further action is required within i915. If the fbdev framebuffer
> has been fully set up, struct fb_ops.fb_destroy implements the
> release. For partially initialized emulation, the fbdev client
> reverts the initial setup.
> 
> v3:
>         * as before, silently ignore devices without displays
> v2:
>         * let drm_client_register() handle initial hotplug
>         * fix driver name in error message (Jani)
>         * fix non-fbdev build (kernel test robot)
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c  |   1 -
>  .../drm/i915/display/intel_display_driver.c   |  18 --
>  drivers/gpu/drm/i915/display/intel_fbdev.c    | 180 ++++++++--------
> --
>  drivers/gpu/drm/i915/display/intel_fbdev.h    |  20 +-
>  drivers/gpu/drm/i915/i915_driver.c            |   2 +
>  5 files changed, 83 insertions(+), 138 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index edbcf5968804d..7efa8d2787c39 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -81,7 +81,6 @@
>  #include "intel_dvo.h"
>  #include "intel_fb.h"
>  #include "intel_fbc.h"
> -#include "intel_fbdev.h"
>  #include "intel_fdi.h"
>  #include "intel_fifo_underrun.h"
>  #include "intel_frontbuffer.h"
> diff --git a/drivers/gpu/drm/i915/display/intel_display_driver.c
> b/drivers/gpu/drm/i915/display/intel_display_driver.c
> index ffdcddd1943e0..213a4ee93ffc2 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_driver.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_driver.c
> @@ -364,10 +364,6 @@ int intel_display_driver_probe(struct
> drm_i915_private *i915)
>  
>         intel_overlay_setup(i915);
>  
> -       ret = intel_fbdev_init(&i915->drm);
> -       if (ret)
> -               return ret;
> -
>         /* Only enable hotplug handling once the fbdev is fully set
> up. */
>         intel_hpd_init(i915);
>         intel_hpd_poll_disable(i915);
> @@ -392,16 +388,6 @@ void intel_display_driver_register(struct
> drm_i915_private *i915)
>  
>         intel_display_debugfs_register(i915);
>  
> -       /*
> -        * Some ports require correctly set-up hpd registers for
> -        * detection to work properly (leading to ghost connected
> -        * connector status), e.g. VGA on gm45.  Hence we can only
> set
> -        * up the initial fbdev config after hpd irqs are fully
> -        * enabled. We do it last so that the async config cannot run
> -        * before the connectors are registered.
> -        */
> -       intel_fbdev_initial_config_async(i915);
> -
>         /*
>          * We need to coordinate the hotplugs with the asynchronous
>          * fbdev configuration, for which we use the
> @@ -445,9 +431,6 @@ void intel_display_driver_remove_noirq(struct
> drm_i915_private *i915)
>          */
>         intel_hpd_poll_fini(i915);
>  
> -       /* poll work can call into fbdev, hence clean that up
> afterwards */
> -       intel_fbdev_fini(i915);
> -
>         intel_unregister_dsm_handler();
>  
>         /* flush any delayed tasks or pending work */
> @@ -484,7 +467,6 @@ void intel_display_driver_unregister(struct
> drm_i915_private *i915)
>         if (!HAS_DISPLAY(i915))
>                 return;
>  
> -       intel_fbdev_unregister(i915);
>         intel_audio_deinit(i915);
>  
>         /*
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c
> b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index 39de61d4e7906..100a4aaf1b7e4 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -24,7 +24,6 @@
>   *     David Airlie
>   */
>  
> -#include <linux/async.h>
>  #include <linux/console.h>
>  #include <linux/delay.h>
>  #include <linux/errno.h>
> @@ -39,6 +38,7 @@
>  #include <linux/vga_switcheroo.h>
>  
>  #include <drm/drm_crtc.h>
> +#include <drm/drm_crtc_helper.h>
>  #include <drm/drm_fb_helper.h>
>  #include <drm/drm_fourcc.h>
>  #include <drm/drm_gem_framebuffer_helper.h>
> @@ -58,7 +58,6 @@ struct intel_fbdev {
>         struct intel_framebuffer *fb;
>         struct i915_vma *vma;
>         unsigned long vma_flags;
> -       async_cookie_t cookie;
>         int preferred_bpp;
>  
>         /* Whether or not fbdev hpd processing is temporarily
> suspended */
> @@ -135,6 +134,26 @@ static int intel_fbdev_mmap(struct fb_info
> *info, struct vm_area_struct *vma)
>         return i915_gem_fb_mmap(obj, vma);
>  }
>  
> +static void intel_fbdev_fb_destroy(struct fb_info *info)
> +{
> +       struct drm_fb_helper *fb_helper = info->par;
> +       struct intel_fbdev *ifbdev = container_of(fb_helper, struct
> intel_fbdev, helper);
> +
> +       drm_fb_helper_fini(&ifbdev->helper);
> +
> +       /*
> +        * We rely on the object-free to release the VMA pinning for
> +        * the info->screen_base mmaping. Leaking the VMA is simpler
> than
> +        * trying to rectify all the possible error paths leading
> here.
> +        */
> +       intel_unpin_fb_vma(ifbdev->vma, ifbdev->vma_flags);
> +       drm_framebuffer_remove(&ifbdev->fb->base);
> +
> +       drm_client_release(&fb_helper->client);
> +       drm_fb_helper_unprepare(&ifbdev->helper);
> +       kfree(ifbdev);
> +}
> +
>  static const struct fb_ops intelfb_ops = {
>         .owner = THIS_MODULE,
>         __FB_DEFAULT_DEFERRED_OPS_RDWR(intel_fbdev),
> @@ -144,6 +163,7 @@ static const struct fb_ops intelfb_ops = {
>         .fb_pan_display = intel_fbdev_pan_display,
>         __FB_DEFAULT_DEFERRED_OPS_DRAW(intel_fbdev),
>         .fb_mmap = intel_fbdev_mmap,
> +       .fb_destroy = intel_fbdev_fb_destroy,
>  };
>  
>  static int intelfb_alloc(struct drm_fb_helper *helper,
> @@ -212,7 +232,6 @@ static int intelfb_create(struct drm_fb_helper
> *helper,
>         struct intel_framebuffer *intel_fb = ifbdev->fb;
>         struct drm_device *dev = helper->dev;
>         struct drm_i915_private *dev_priv = to_i915(dev);
> -       struct pci_dev *pdev = to_pci_dev(dev_priv->drm.dev);
>         struct i915_ggtt *ggtt = to_gt(dev_priv)->ggtt;
>         const struct i915_gtt_view view = {
>                 .type = I915_GTT_VIEW_NORMAL,
> @@ -337,7 +356,7 @@ static int intelfb_create(struct drm_fb_helper
> *helper,
>         ifbdev->vma_flags = flags;
>  
>         intel_runtime_pm_put(&dev_priv->runtime_pm, wakeref);
> -       vga_switcheroo_client_fb_set(pdev, info);
> +
>         return 0;
>  
>  out_unpin:
> @@ -363,26 +382,6 @@ static const struct drm_fb_helper_funcs
> intel_fb_helper_funcs = {
>         .fb_dirty = intelfb_dirty,
>  };
>  
> -static void intel_fbdev_destroy(struct intel_fbdev *ifbdev)
> -{
> -       /* We rely on the object-free to release the VMA pinning for
> -        * the info->screen_base mmaping. Leaking the VMA is simpler
> than
> -        * trying to rectify all the possible error paths leading
> here.
> -        */
> -
> -       drm_fb_helper_fini(&ifbdev->helper);
> -
> -       if (ifbdev->vma)
> -               intel_unpin_fb_vma(ifbdev->vma, ifbdev->vma_flags);
> -
> -       if (ifbdev->fb)
> -               drm_framebuffer_remove(&ifbdev->fb->base);
> -
> -       drm_client_release(&ifbdev->helper.client);
> -       drm_fb_helper_unprepare(&ifbdev->helper);
> -       kfree(ifbdev);
> -}
> -
>  /*
>   * Build an intel_fbdev struct using a BIOS allocated framebuffer,
> if possible.
>   * The core display code will have read out the current plane
> configuration,
> @@ -546,16 +545,6 @@ static void intel_fbdev_suspend_worker(struct
> work_struct *work)
>                                 true);
>  }
>  
> -static void intel_fbdev_sync(struct intel_fbdev *ifbdev)
> -{
> -       if (!ifbdev->cookie)
> -               return;
> -
> -       /* Only serialises with all preceding async calls, hence +1
> */
> -       async_synchronize_cookie(ifbdev->cookie + 1);
> -       ifbdev->cookie = 0;
> -}
> -
>  /* Suspends/resumes fbdev processing of incoming HPD events. When
> resuming HPD
>   * processing, fbdev will perform a full connector reprobe if a
> hotplug event
>   * was received while HPD was suspended.
> @@ -646,8 +635,6 @@ static void
> intel_fbdev_output_poll_changed(struct drm_device *dev)
>         if (!ifbdev)
>                 return;
>  
> -       intel_fbdev_sync(ifbdev);
> -
>         mutex_lock(&ifbdev->hpd_lock);
>         send_hpd = !ifbdev->hpd_suspended;
>         ifbdev->hpd_waiting = true;
> @@ -664,7 +651,6 @@ static void intel_fbdev_restore_mode(struct
> drm_i915_private *dev_priv)
>         if (!ifbdev)
>                 return;
>  
> -       intel_fbdev_sync(ifbdev);
>         if (!ifbdev->vma)
>                 return;
>  
> @@ -677,7 +663,20 @@ static void intel_fbdev_restore_mode(struct
> drm_i915_private *dev_priv)
>   */
>  
>  static void intel_fbdev_client_unregister(struct drm_client_dev
> *client)
> -{ }
> +{
> +       struct drm_fb_helper *fb_helper =
> drm_fb_helper_from_client(client);
> +       struct drm_device *dev = fb_helper->dev;
> +       struct pci_dev *pdev = to_pci_dev(dev->dev);
> +
> +       if (fb_helper->info) {
> +               vga_switcheroo_client_fb_set(pdev, NULL);
> +               drm_fb_helper_unregister_info(fb_helper);
> +       } else {
> +               drm_fb_helper_unprepare(fb_helper);
> +               drm_client_release(&fb_helper->client);
> +               kfree(fb_helper);
> +       }
> +}
>  
>  static int intel_fbdev_client_restore(struct drm_client_dev *client)
>  {
> @@ -691,9 +690,36 @@ static int intel_fbdev_client_restore(struct
> drm_client_dev *client)
>  
>  static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
>  {
> -       intel_fbdev_output_poll_changed(client->dev);
> +       struct drm_fb_helper *fb_helper =
> drm_fb_helper_from_client(client);
> +       struct drm_device *dev = client->dev;
> +       struct pci_dev *pdev = to_pci_dev(dev->dev);
> +       int ret;
> +
> +       if (dev->fb_helper) {
> +               intel_fbdev_output_poll_changed(dev);
> +               return 0;
> +       }
> +
> +       ret = drm_fb_helper_init(dev, fb_helper);
> +       if (ret)
> +               goto err_drm_err;
> +
> +       if (!drm_drv_uses_atomic_modeset(dev))
> +               drm_helper_disable_unused_functions(dev);

Can you please explain why this is needed here?

> +
> +       ret = drm_fb_helper_initial_config(fb_helper);
> +       if (ret)
> +               goto err_drm_fb_helper_fini;
> +
> +       vga_switcheroo_client_fb_set(pdev, fb_helper->info);
>  
>         return 0;
> +
> +err_drm_fb_helper_fini:
> +       drm_fb_helper_fini(fb_helper);
> +err_drm_err:
> +       drm_err(dev, "Failed to setup i915 fbdev emulation
> (ret=%d)\n", ret);
> +       return ret;
>  }
>  
>  static const struct drm_client_funcs intel_fbdev_client_funcs = {
> @@ -703,22 +729,23 @@ static const struct drm_client_funcs
> intel_fbdev_client_funcs = {
>         .hotplug        = intel_fbdev_client_hotplug,
>  };
>  
> -int intel_fbdev_init(struct drm_device *dev)
> +void intel_fbdev_setup(struct drm_i915_private *dev_priv)

Use i915 rather than dev_priv.

BR,

Jouni Högander

>  {
> -       struct drm_i915_private *dev_priv = to_i915(dev);
> +       struct drm_device *dev = &dev_priv->drm;
>         struct intel_fbdev *ifbdev;
>         int ret;
>  
> -       if (drm_WARN_ON(dev, !HAS_DISPLAY(dev_priv)))
> -               return -ENODEV;
> +       if (!HAS_DISPLAY(dev_priv))
> +               return;
>  
>         ifbdev = kzalloc(sizeof(*ifbdev), GFP_KERNEL);
>         if (!ifbdev)
> -               return -ENOMEM;
> -
> -       mutex_init(&ifbdev->hpd_lock);
> +               return;
>         drm_fb_helper_prepare(dev, &ifbdev->helper, 32,
> &intel_fb_helper_funcs);
>  
> +       dev_priv->display.fbdev.fbdev = ifbdev;
> +       INIT_WORK(&dev_priv->display.fbdev.suspend_work,
> intel_fbdev_suspend_worker);
> +       mutex_init(&ifbdev->hpd_lock);
>         if (intel_fbdev_init_bios(dev, ifbdev))
>                 ifbdev->helper.preferred_bpp = ifbdev->preferred_bpp;
>         else
> @@ -726,68 +753,19 @@ int intel_fbdev_init(struct drm_device *dev)
>  
>         ret = drm_client_init(dev, &ifbdev->helper.client, "i915-
> fbdev",
>                               &intel_fbdev_client_funcs);
> -       if (ret)
> +       if (ret) {
> +               drm_err(dev, "Failed to register client: %d\n", ret);
>                 goto err_drm_fb_helper_unprepare;
> +       }
>  
> -       ret = drm_fb_helper_init(dev, &ifbdev->helper);
> -       if (ret)
> -               goto err_drm_client_release;
> -
> -       dev_priv->display.fbdev.fbdev = ifbdev;
> -       INIT_WORK(&dev_priv->display.fbdev.suspend_work,
> intel_fbdev_suspend_worker);
> +       drm_client_register(&ifbdev->helper.client);
>  
> -       return 0;
> +       return;
>  
> -err_drm_client_release:
> -       drm_client_release(&ifbdev->helper.client);
>  err_drm_fb_helper_unprepare:
>         drm_fb_helper_unprepare(&ifbdev->helper);
> +       mutex_destroy(&ifbdev->hpd_lock);
>         kfree(ifbdev);
> -       return ret;
> -}
> -
> -static void intel_fbdev_initial_config(void *data, async_cookie_t
> cookie)
> -{
> -       struct intel_fbdev *ifbdev = data;
> -
> -       /* Due to peculiar init order wrt to hpd handling this is
> separate. */
> -       if (drm_fb_helper_initial_config(&ifbdev->helper))
> -               intel_fbdev_unregister(to_i915(ifbdev->helper.dev));
> -}
> -
> -void intel_fbdev_initial_config_async(struct drm_i915_private
> *dev_priv)
> -{
> -       struct intel_fbdev *ifbdev = dev_priv->display.fbdev.fbdev;
> -
> -       if (!ifbdev)
> -               return;
> -
> -       ifbdev->cookie = async_schedule(intel_fbdev_initial_config,
> ifbdev);
> -}
> -
> -void intel_fbdev_unregister(struct drm_i915_private *dev_priv)
> -{
> -       struct intel_fbdev *ifbdev = dev_priv->display.fbdev.fbdev;
> -
> -       if (!ifbdev)
> -               return;
> -
> -       intel_fbdev_set_suspend(&dev_priv->drm,
> FBINFO_STATE_SUSPENDED, true);
> -
> -       if (!current_is_async())
> -               intel_fbdev_sync(ifbdev);
> -
> -       drm_fb_helper_unregister_info(&ifbdev->helper);
> -}
> -
> -void intel_fbdev_fini(struct drm_i915_private *dev_priv)
> -{
> -       struct intel_fbdev *ifbdev = fetch_and_zero(&dev_priv-
> >display.fbdev.fbdev);
> -
> -       if (!ifbdev)
> -               return;
> -
> -       intel_fbdev_destroy(ifbdev);
>  }
>  
>  struct intel_framebuffer *intel_fbdev_framebuffer(struct intel_fbdev
> *fbdev)
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.h
> b/drivers/gpu/drm/i915/display/intel_fbdev.h
> index 8c953f102ba22..08de2d5b34338 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.h
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.h
> @@ -14,27 +14,11 @@ struct intel_fbdev;
>  struct intel_framebuffer;
>  
>  #ifdef CONFIG_DRM_FBDEV_EMULATION
> -int intel_fbdev_init(struct drm_device *dev);
> -void intel_fbdev_initial_config_async(struct drm_i915_private
> *dev_priv);
> -void intel_fbdev_unregister(struct drm_i915_private *dev_priv);
> -void intel_fbdev_fini(struct drm_i915_private *dev_priv);
> +void intel_fbdev_setup(struct drm_i915_private *dev_priv);
>  void intel_fbdev_set_suspend(struct drm_device *dev, int state, bool
> synchronous);
>  struct intel_framebuffer *intel_fbdev_framebuffer(struct intel_fbdev
> *fbdev);
>  #else
> -static inline int intel_fbdev_init(struct drm_device *dev)
> -{
> -       return 0;
> -}
> -
> -static inline void intel_fbdev_initial_config_async(struct
> drm_i915_private *dev_priv)
> -{
> -}
> -
> -static inline void intel_fbdev_unregister(struct drm_i915_private
> *dev_priv)
> -{
> -}
> -
> -static inline void intel_fbdev_fini(struct drm_i915_private
> *dev_priv)
> +static inline void intel_fbdev_setup(struct drm_i915_private
> *dev_priv)
>  {
>  }
>  
> diff --git a/drivers/gpu/drm/i915/i915_driver.c
> b/drivers/gpu/drm/i915/i915_driver.c
> index 86460cd8167d1..53663c0cc3be4 100644
> --- a/drivers/gpu/drm/i915/i915_driver.c
> +++ b/drivers/gpu/drm/i915/i915_driver.c
> @@ -817,6 +817,8 @@ int i915_driver_probe(struct pci_dev *pdev, const
> struct pci_device_id *ent)
>  
>         i915->do_release = true;
>  
> +       intel_fbdev_setup(i915);
> +
>         return 0;
>  
>  out_cleanup_gem: