Re: [PATCH 8/9] drm: Add infrastructure for platform devices

[Thomas Zimmermann <tzimmermann@suse.de>]

[-- Attachment #1.1.1: Type: text/plain, Size: 9928 bytes --]

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@suse.de>
> 
> 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.

Any specific reason for drm-kms?

The aperture helpers are used to manage ownership of memory and most
drivers begin with drm_fb_helper_remove_conflicting_framebuffers(). It
seems more approprite to put this into drm-internals as part of the
driver initialization.

Best regards
Thomas

> - naming isn't super ocd with drm_platform.c but that prefix not used, but
>   I also don't have better ideas.
> - 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?
> 
> 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


[-- Attachment #1.2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 516 bytes --]

[-- Attachment #2: Type: text/plain, Size: 160 bytes --]

_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel