On Mon, Sep 28, 2020 at 10:40 AM Thomas Zimmermann <tzimmermann@xxxxxxx> wrote:
>
> Hi
>
> Am 29.06.20 um 11:27 schrieb Daniel Vetter:
> > On Thu, Jun 25, 2020 at 02:00:10PM +0200, Thomas Zimmermann wrote:
> >> Platform devices might operate on firmware framebuffers, such as VESA or
> >> EFI. Before a native driver for the graphics hardware can take over the
> >> device, it has to remove any platform driver that operates on the firmware
> >> framebuffer. Platform helpers provide the infrastructure for platform
> >> drivers to acquire firmware framebuffers, and for native drivers to remove
> >> them lateron.
> >>
> >> It works similar to the related fbdev mechanism. During initialization, the
> >> platform driver acquires the firmware framebuffer's I/O memory and provides
> >> a callback to be removed. The native driver later uses this inforamtion to
> >> remove any platform driver for it's framebuffer I/O memory.
> >>
> >> The platform helper's removal code is integrated into the existing code for
> >> removing conflicting fraembuffers, so native drivers use it automatically.
> >>
> >> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> >
> > I have some ideas for how to do this a notch cleaner in the next patch.
> > Maybe best to discuss the actual implmenentation stuff there.
> >
> > Aside from that usual nits:
> > - kerneldoc for these please, pulled into drm-kms.rst.
> > - naming isn't super ocd with drm_platform.c but that prefix not used, but
> > I also don't have better ideas.
>
> I was never really happy with the naming either. Maybe call it aperture
> helpers with drm_aperture_ and CONFIG_DRM_APERTURE_HELPER?
+1
> > - I think the functions from drm_fb_helper.h for removing other
> > framebuffers should be moved here, and function name prefix adjusted
> > acoordingly
> >
> > I'm wondering about the locking and deadlock potential here, is lockdep
> > all happy with this?
>
> I haven't seen any complains, but I'll double check.
Might be worth it to cc Greg on this, since the device driver model
has a lot of corner cases to make sure it doesn't get stuck here with
hiararchical drivers/device getting removed while something else is
probing them at the same time.
-Daniel
> Best regards
> Thomas
>
> >
> > Cheers, Daniel
> >
> >> ---
> >> drivers/gpu/drm/Kconfig | 6 ++
> >> drivers/gpu/drm/Makefile | 1 +
> >> drivers/gpu/drm/drm_platform.c | 118 +++++++++++++++++++++++++++++++++
> >> include/drm/drm_fb_helper.h | 18 ++++-
> >> include/drm/drm_platform.h | 42 ++++++++++++
> >> 5 files changed, 184 insertions(+), 1 deletion(-)
> >> create mode 100644 drivers/gpu/drm/drm_platform.c
> >> create mode 100644 include/drm/drm_platform.h
> >>
> >> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> >> index c4fd57d8b717..e9d6892f9d38 100644
> >> --- a/drivers/gpu/drm/Kconfig
> >> +++ b/drivers/gpu/drm/Kconfig
> >> @@ -229,6 +229,12 @@ config DRM_SCHED
> >> tristate
> >> depends on DRM
> >>
> >> +config DRM_PLATFORM_HELPER
> >> + bool
> >> + depends on DRM
> >> + help
> >> + Helpers for DRM platform devices
> >> +
> >> source "drivers/gpu/drm/i2c/Kconfig"
> >>
> >> source "drivers/gpu/drm/arm/Kconfig"
> >> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> >> index 2c0e5a7e5953..8ceb21d0770a 100644
> >> --- a/drivers/gpu/drm/Makefile
> >> +++ b/drivers/gpu/drm/Makefile
> >> @@ -32,6 +32,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
> >> drm-$(CONFIG_PCI) += drm_pci.o
> >> drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
> >> drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> >> +drm-$(CONFIG_DRM_PLATFORM_HELPER) += drm_platform.o
> >>
> >> drm_vram_helper-y := drm_gem_vram_helper.o
> >> obj-$(CONFIG_DRM_VRAM_HELPER) += drm_vram_helper.o
> >> diff --git a/drivers/gpu/drm/drm_platform.c b/drivers/gpu/drm/drm_platform.c
> >> new file mode 100644
> >> index 000000000000..09a2f2a31aa5
> >> --- /dev/null
> >> +++ b/drivers/gpu/drm/drm_platform.c
> >> @@ -0,0 +1,118 @@
> >> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> >> +
> >> +#include <linux/mutex.h>
> >> +#include <linux/slab.h>
> >> +
> >> +#include <drm/drm_drv.h>
> >> +#include <drm/drm_managed.h>
> >> +#include <drm/drm_platform.h>
> >> +
> >> +static LIST_HEAD(drm_apertures);
> >> +
> >> +static DEFINE_MUTEX(drm_apertures_lock);
> >> +
> >> +static bool overlap(resource_size_t base1, resource_size_t end1,
> >> + resource_size_t base2, resource_size_t end2)
> >> +{
> >> + return (base1 < end2) && (end1 > base2);
> >> +}
> >> +
> >> +static struct drm_aperture *
> >> +drm_aperture_acquire(struct drm_device *dev,
> >> + resource_size_t base, resource_size_t size,
> >> + const struct drm_aperture_funcs *funcs)
> >> +{
> >> + size_t end = base + size;
> >> + struct list_head *pos;
> >> + struct drm_aperture *ap;
> >> +
> >> + mutex_lock(&drm_apertures_lock);
> >> +
> >> + list_for_each(pos, &drm_apertures) {
> >> + ap = container_of(pos, struct drm_aperture, lh);
> >> + if (overlap(base, end, ap->base, ap->base + ap->size))
> >> + return ERR_PTR(-EBUSY);
> >> + }
> >> +
> >> + ap = drmm_kzalloc(dev, sizeof(*ap), GFP_KERNEL);
> >> + if (!ap)
> >> + return ERR_PTR(-ENOMEM);
> >> +
> >> + ap->dev = dev;
> >> + ap->base = base;
> >> + ap->size = size;
> >> + ap->funcs = funcs;
> >> + INIT_LIST_HEAD(&ap->lh);
> >> +
> >> + list_add(&ap->lh, &drm_apertures);
> >> +
> >> + mutex_unlock(&drm_apertures_lock);
> >> +
> >> + return ap;
> >> +}
> >> +
> >> +static void drm_aperture_release(struct drm_aperture *ap)
> >> +{
> >> + bool kicked_out = ap->kicked_out;
> >> +
> >> + if (!kicked_out)
> >> + mutex_lock(&drm_apertures_lock);
> >> +
> >> + list_del(&ap->lh);
> >> + if (ap->funcs->release)
> >> + ap->funcs->release(ap);
> >> +
> >> + if (!kicked_out)
> >> + mutex_unlock(&drm_apertures_lock);
> >> +}
> >> +
> >> +static void drm_aperture_acquire_release(struct drm_device *dev, void *ptr)
> >> +{
> >> + struct drm_aperture *ap = ptr;
> >> +
> >> + drm_aperture_release(ap);
> >> +}
> >> +
> >> +struct drm_aperture *
> >> +drmm_aperture_acquire(struct drm_device *dev,
> >> + resource_size_t base, resource_size_t size,
> >> + const struct drm_aperture_funcs *funcs)
> >> +{
> >> + struct drm_aperture *ap;
> >> + int ret;
> >> +
> >> + ap = drm_aperture_acquire(dev, base, size, funcs);
> >> + if (IS_ERR(ap))
> >> + return ap;
> >> + ret = drmm_add_action_or_reset(dev, drm_aperture_acquire_release, ap);
> >> + if (ret)
> >> + return ERR_PTR(ret);
> >> +
> >> + return ap;
> >> +}
> >> +EXPORT_SYMBOL(drmm_aperture_acquire);
> >> +
> >> +void drm_kickout_apertures_at(resource_size_t base, resource_size_t size)
> >> +{
> >> + resource_size_t end = base + size;
> >> + struct list_head *pos, *n;
> >> +
> >> + mutex_lock(&drm_apertures_lock);
> >> +
> >> + list_for_each_safe(pos, n, &drm_apertures) {
> >> + struct drm_aperture *ap =
> >> + container_of(pos, struct drm_aperture, lh);
> >> +
> >> + if (!overlap(base, end, ap->base, ap->base + ap->size))
> >> + continue;
> >> +
> >> + ap->kicked_out = true;
> >> + if (ap->funcs->kickout)
> >> + ap->funcs->kickout(ap);
> >> + else
> >> + drm_dev_put(ap->dev);
> >> + }
> >> +
> >> + mutex_unlock(&drm_apertures_lock);
> >> +}
> >> +EXPORT_SYMBOL(drm_kickout_apertures_at);
> >> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> >> index 306aa3a60be9..a919b78b1961 100644
> >> --- a/include/drm/drm_fb_helper.h
> >> +++ b/include/drm/drm_fb_helper.h
> >> @@ -35,7 +35,9 @@ struct drm_fb_helper;
> >> #include <drm/drm_client.h>
> >> #include <drm/drm_crtc.h>
> >> #include <drm/drm_device.h>
> >> +#include <drm/drm_platform.h>
> >> #include <linux/kgdb.h>
> >> +#include <linux/pci.h>
> >> #include <linux/vgaarb.h>
> >>
> >> enum mode_set_atomic {
> >> @@ -465,6 +467,11 @@ static inline int
> >> drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
> >> const char *name, bool primary)
> >> {
> >> + int i;
> >> +
> >> + for (i = 0; i < a->count; ++i)
> >> + drm_kickout_apertures_at(a->ranges[i].base, a->ranges[i].size);
> >> +
> >> #if IS_REACHABLE(CONFIG_FB)
> >> return remove_conflicting_framebuffers(a, name, primary);
> >> #else
> >> @@ -487,7 +494,16 @@ static inline int
> >> drm_fb_helper_remove_conflicting_pci_framebuffers(struct pci_dev *pdev,
> >> const char *name)
> >> {
> >> - int ret = 0;
> >> + resource_size_t base, size;
> >> + int bar, ret = 0;
> >> +
> >> + for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> >> + if (!(pci_resource_flags(pdev, bar) & IORESOURCE_MEM))
> >> + continue;
> >> + base = pci_resource_start(pdev, bar);
> >> + size = pci_resource_len(pdev, bar);
> >> + drm_kickout_apertures_at(base, size);
> >> + }
> >>
> >> /*
> >> * WARNING: Apparently we must kick fbdev drivers before vgacon,
> >> diff --git a/include/drm/drm_platform.h b/include/drm/drm_platform.h
> >> new file mode 100644
> >> index 000000000000..475e88ee1fbd
> >> --- /dev/null
> >> +++ b/include/drm/drm_platform.h
> >> @@ -0,0 +1,42 @@
> >> +// SPDX-License-Identifier: GPL-2.0 OR MIT
> >> +
> >> +#ifndef _DRM_PLATFORM_H_
> >> +#define _DRM_PLATFORM_H_
> >> +
> >> +#include <linux/list.h>
> >> +#include <linux/types.h>
> >> +
> >> +struct drm_aperture;
> >> +struct drm_device;
> >> +
> >> +struct drm_aperture_funcs {
> >> + void (*kickout)(struct drm_aperture *ap);
> >> + void (*release)(struct drm_aperture *ap);
> >> +};
> >> +
> >> +struct drm_aperture {
> >> + struct drm_device *dev;
> >> + resource_size_t base;
> >> + resource_size_t size;
> >> +
> >> + const struct drm_aperture_funcs *funcs;
> >> +
> >> + struct list_head lh;
> >> + bool kicked_out;
> >> +};
> >> +
> >> +struct drm_aperture *
> >> +drmm_aperture_acquire(struct drm_device *dev,
> >> + resource_size_t base, resource_size_t size,
> >> + const struct drm_aperture_funcs *funcs);
> >> +
> >> +#if defined (CONFIG_DRM_PLATFORM_HELPER)
> >> +void drm_kickout_apertures_at(resource_size_t base, resource_size_t size);
> >> +#else
> >> +static inline void
> >> +drm_kickout_apertures_at(resource_size_t base, resource_size_t size)
> >> +{
> >> +}
> >> +#endif
> >> +
> >> +#endif
> >> --
> >> 2.27.0
> >>
> >
>
> --
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Felix Imendörffer
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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