Re: [PATCH v2 5/5] drm/ingenic: Add option to alloc cached GEM buffers

Paul Cercueil
2021-03-11T12:11:53Z

Le jeu. 11 mars 2021 à 10:27, Hillf Danton <hdanton@sina.com> a écrit
:
> On Wed, 10 Mar 2021 19:01:01 +0000 Paul Cercueil wrote:
>> Le lun. 8 mars 2021 11:47, Hillf Danton <hdanton@sina.com> a crit :
>>> On Sun, 7 Mar 2021 20:28:35 +0000 Paul Cercueil wrote:
>>>> With the module parameter ingenic-drm.cached_gem_buffers, it is
>>>> possible
>>>> to specify that we want GEM buffers backed by non-coherent
>>>> memory.
>>>>
>>>> This dramatically speeds up software rendering on Ingenic SoCs,
>>>> even for
>>>> tasks where write-combine memory should in theory be faster (e.g.
>>>> simple
>>>> blits).
>>>
>>> Wondering if it is due to the tricks at [1].
>>>
>>> If so, is dma_alloc_noncoherent() necessary in this patchset?
>>
>> You confuse non-contiguous with non-coherent, which are two different
>> things.
>
> You misunderstood me. From [1] we know coherent caching is arch thing,
> so your proposal is not mandatory on ARM IMHO - what baffles me is
> noncoherent back memory can speed up device, coherent ot not,
> regardless
> of arch. Can you point me to the reasons behind your speedup?

Well, I did write in the cover letter that it would help *some* SoCs,
so it is not meant to be a default setting. As you can see in the last
patch, it is opt-in. Ingenic SoCs are MIPS SoCs, btw.

One thing I should add is that this speeds up *software* rendering (vs.
write-combine). It makes perfect sense that it speeds up things like
alpha-blending, but I can't explain why it speeds up standard blits. My
guess is that cache line invalidation is just extremely fast on this
SoC.

-Paul

>>
>> Cheers,
>> -Paul
>>
>>> Christoph can you give us a concise lesson on noncoherency covering
>>> at least
>>> noncoherent device, noncoherent memory(used in this work), no
>>> coherent
>>> caching(in [1]), their links to speedup, and the thumb rule to
>>> handle
>>> noncoherency in workdays. It feels toe curling every time I see
>>> noncoherence
>>> going downtown with speedup hand in hand.
>>>
>>> [1] Subject: [PATCH 6/6] media: uvcvideo: Use
>>> dma_alloc_noncontiguos
>>> API
>>> https://lore.kernel.org/lkml/20210301085236.947011-7-hch@lst.de/#t
>>>
>>>>
>>>> Leave it disabled by default, since it is specific to one
>>>> use-case
>>>> (software rendering).
>>>>
>>>> v2: Rework code to work with new DRM APIs regarding plane states
>>>>
>>>> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
>>>> ---
>>>> drivers/gpu/drm/ingenic/ingenic-drm-drv.c | 49
>>>> ++++++++++++++++++++++-
>>>> drivers/gpu/drm/ingenic/ingenic-drm.h | 4 ++
>>>> drivers/gpu/drm/ingenic/ingenic-ipu.c | 14 ++++++-
>>>> 3 files changed, 63 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>>>> b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>>>> index d60e1eefc9d1..ba1ac0fcda74 100644
>>>> --- a/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>>>> +++ b/drivers/gpu/drm/ingenic/ingenic-drm-drv.c
>>>> @@ -9,6 +9,7 @@
>>>> #include <linux/component.h>
>>>> #include <linux/clk.h>
>>>> #include <linux/dma-mapping.h>
>>>> +#include <linux/io.h>
>>>> #include <linux/module.h>
>>>> #include <linux/mutex.h>
>>>> #include <linux/of_device.h>
>>>> @@ -23,6 +24,7 @@
>>>> #include <drm/drm_color_mgmt.h>
>>>> #include <drm/drm_crtc.h>
>>>> #include <drm/drm_crtc_helper.h>
>>>> +#include <drm/drm_damage_helper.h>
>>>> #include <drm/drm_drv.h>
>>>> #include <drm/drm_gem_cma_helper.h>
>>>> #include <drm/drm_fb_cma_helper.h>
>>>> @@ -99,6 +101,11 @@ struct ingenic_drm {
>>>> struct notifier_block clock_nb;
>>>> };
>>>>
>>>> +static bool ingenic_drm_cached_gem_buf;
>>>> +module_param_named(cached_gem_buffers,
>>>> ingenic_drm_cached_gem_buf,
>>>> bool, 0400);
>>>> +MODULE_PARM_DESC(cached_gem_buffers,
>>>> + "Enable fully cached GEM buffers [default=false]");
>>>> +
>>>> static bool ingenic_drm_writeable_reg(struct device *dev,
>>>> unsigned
>>>> int reg)
>>>> {
>>>> switch (reg) {
>>>> @@ -410,6 +417,8 @@ static int
>>>> ingenic_drm_plane_atomic_check(struct drm_plane *plane,
>>>> old_plane_state->fb->format->format !=
>>>> new_plane_state->fb->format->format))
>>>> crtc_state->mode_changed = true;
>>>>
>>>> + drm_atomic_helper_check_plane_damage(state, new_plane_state);
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>> @@ -541,10 +550,20 @@ static void
>>>> ingenic_drm_update_palette(struct
>>>> ingenic_drm *priv,
>>>> }
>>>> }
>>>>
>>>> +void ingenic_drm_sync_data(struct device *dev,
>>>> + struct drm_plane_state *old_state,
>>>> + struct drm_plane_state *state)
>>>> +{
>>>> + if (ingenic_drm_cached_gem_buf)
>>>> + drm_gem_cma_sync_data(dev, old_state, state);
>>>> +}
>>>> +
>>>> static void ingenic_drm_plane_atomic_update(struct drm_plane
>>>> *plane,
>>>> struct drm_atomic_state *state)
>>>> {
>>>> struct ingenic_drm *priv = drm_device_get_priv(plane->dev);
>>>> + struct drm_plane_state *oldstate =
>>>> drm_atomic_get_old_plane_state(state,
>>>> + plane);
>>>> struct drm_plane_state *newstate =
>>>> drm_atomic_get_new_plane_state(state,
>>>> plane);
>>>> struct drm_crtc_state *crtc_state;
>>>> @@ -554,6 +573,8 @@ static void
>>>> ingenic_drm_plane_atomic_update(struct drm_plane *plane,
>>>> u32 fourcc;
>>>>
>>>> if (newstate && newstate->fb) {
>>>> + ingenic_drm_sync_data(priv->dev, oldstate, newstate);
>>>> +
>>>> crtc_state = newstate->crtc->state;
>>>>
>>>> addr = drm_fb_cma_get_gem_addr(newstate->fb, newstate, 0);
>>>> @@ -743,6 +764,26 @@ static void
>>>> ingenic_drm_disable_vblank(struct
>>>> drm_crtc *crtc)
>>>> regmap_update_bits(priv->map, JZ_REG_LCD_CTRL,
>>>> JZ_LCD_CTRL_EOF_IRQ, 0);
>>>> }
>>>>
>>>> +static struct drm_framebuffer *
>>>> +ingenic_drm_gem_fb_create(struct drm_device *dev, struct
>>>> drm_file
>>>> *file,
>>>> + const struct drm_mode_fb_cmd2 *mode_cmd)
>>>> +{
>>>> + if (ingenic_drm_cached_gem_buf)
>>>> + return drm_gem_fb_create_with_dirty(dev, file, mode_cmd);
>>>> +
>>>> + return drm_gem_fb_create(dev, file, mode_cmd);
>>>> +}
>>>> +
>>>> +static int ingenic_drm_gem_cma_dumb_create(struct drm_file
>>>> *file_priv,
>>>> + struct drm_device *drm,
>>>> + struct drm_mode_create_dumb *args)
>>>> +{
>>>> + if (ingenic_drm_cached_gem_buf)
>>>> + return drm_gem_cma_dumb_create_noncoherent(file_priv, drm,
>>>> args);
>>>> +
>>>> + return drm_gem_cma_dumb_create(file_priv, drm, args);
>>>> +}
>>>> +
>>>> DEFINE_DRM_GEM_CMA_FOPS(ingenic_drm_fops);
>>>>
>>>> static const struct drm_driver ingenic_drm_driver_data = {
>>>> @@ -755,7 +796,7 @@ static const struct drm_driver
>>>> ingenic_drm_driver_data = {
>>>> .patchlevel = 0,
>>>>
>>>> .fops = &ingenic_drm_fops,
>>>> - DRM_GEM_CMA_DRIVER_OPS,
>>>>
>>>>
>>>> + DRM_GEM_CMA_DRIVER_OPS_WITH_DUMB_CREATE(ingenic_drm_gem_cma_dumb_create),
>>>>
>>>> .irq_handler = ingenic_drm_irq_handler,
>>>> };
>>>> @@ -805,7 +846,7 @@ static const struct drm_encoder_helper_funcs
>>>> ingenic_drm_encoder_helper_funcs =
>>>> };
>>>>
>>>> static const struct drm_mode_config_funcs
>>>> ingenic_drm_mode_config_funcs = {
>>>> - .fb_create = drm_gem_fb_create,
>>>> + .fb_create = ingenic_drm_gem_fb_create,
>>>> .output_poll_changed = drm_fb_helper_output_poll_changed,
>>>> .atomic_check = drm_atomic_helper_check,
>>>> .atomic_commit = drm_atomic_helper_commit,
>>>> @@ -962,6 +1003,8 @@ static int ingenic_drm_bind(struct device
>>>> *dev, bool has_components)
>>>> return ret;
>>>> }
>>>>
>>>> + drm_plane_enable_fb_damage_clips(&priv->f1);
>>>> +
>>>> drm_crtc_helper_add(&priv->crtc,
>>>> &ingenic_drm_crtc_helper_funcs);
>>>>
>>>> ret = drm_crtc_init_with_planes(drm, &priv->crtc, primary,
>>>> @@ -990,6 +1033,8 @@ static int ingenic_drm_bind(struct device
>>>> *dev, bool has_components)
>>>> return ret;
>>>> }
>>>>
>>>> + drm_plane_enable_fb_damage_clips(&priv->f0);
>>>> +
>>>> if (IS_ENABLED(CONFIG_DRM_INGENIC_IPU) && has_components) {
>>>> ret = component_bind_all(dev, drm);
>>>> if (ret) {
>>>> diff --git a/drivers/gpu/drm/ingenic/ingenic-drm.h
>>>> b/drivers/gpu/drm/ingenic/ingenic-drm.h
>>>> index 1b4347f7f084..b6bca356e024 100644
>>>> --- a/drivers/gpu/drm/ingenic/ingenic-drm.h
>>>> +++ b/drivers/gpu/drm/ingenic/ingenic-drm.h
>>>> @@ -185,6 +185,10 @@ void ingenic_drm_plane_config(struct device
>>>> *dev,
>>>> struct drm_plane *plane, u32 fourcc);
>>>> void ingenic_drm_plane_disable(struct device *dev, struct
>>>> drm_plane *plane);
>>>>
>>>> +void ingenic_drm_sync_data(struct device *dev,
>>>> + struct drm_plane_state *old_state,
>>>> + struct drm_plane_state *state);
>>>> +
>>>> extern struct platform_driver *ingenic_ipu_driver_ptr;
>>>>
>>>> #endif /* DRIVERS_GPU_DRM_INGENIC_INGENIC_DRM_H */
>>>> diff --git a/drivers/gpu/drm/ingenic/ingenic-ipu.c
>>>> b/drivers/gpu/drm/ingenic/ingenic-ipu.c
>>>> index 5ae6adab8306..7826eab044ba 100644
>>>> --- a/drivers/gpu/drm/ingenic/ingenic-ipu.c
>>>> +++ b/drivers/gpu/drm/ingenic/ingenic-ipu.c
>>>> @@ -20,6 +20,7 @@
>>>>
>>>> #include <drm/drm_atomic.h>
>>>> #include <drm/drm_atomic_helper.h>
>>>> +#include <drm/drm_damage_helper.h>
>>>> #include <drm/drm_drv.h>
>>>> #include <drm/drm_fb_cma_helper.h>
>>>> #include <drm/drm_fourcc.h>
>>>> @@ -285,6 +286,8 @@ static void
>>>> ingenic_ipu_plane_atomic_update(struct drm_plane *plane,
>>>> struct drm_atomic_state *state)
>>>> {
>>>> struct ingenic_ipu *ipu = plane_to_ingenic_ipu(plane);
>>>> + struct drm_plane_state *oldstate =
>>>> drm_atomic_get_old_plane_state(state,
>>>> + plane);
>>>> struct drm_plane_state *newstate =
>>>> drm_atomic_get_new_plane_state(state,
>>>> plane);
>>>> const struct drm_format_info *finfo;
>>>> @@ -317,6 +320,8 @@ static void
>>>> ingenic_ipu_plane_atomic_update(struct drm_plane *plane,
>>>> JZ_IPU_CTRL_CHIP_EN | JZ_IPU_CTRL_LCDC_SEL);
>>>> }
>>>>
>>>> + ingenic_drm_sync_data(ipu->master, oldstate, newstate);
>>>> +
>>>> /* New addresses will be committed in vblank handler... */
>>>> ipu->addr_y = drm_fb_cma_get_gem_addr(newstate->fb, newstate,
>>>> 0);
>>>> if (finfo->num_planes > 1)
>>>> @@ -541,7 +546,7 @@ static int
>>>> ingenic_ipu_plane_atomic_check(struct drm_plane *plane,
>>>>
>>>> if (!new_plane_state->crtc ||
>>>> !crtc_state->mode.hdisplay || !crtc_state->mode.vdisplay)
>>>> - return 0;
>>>> + goto out_check_damage;
>>>>
>>>> /* Plane must be fully visible */
>>>> if (new_plane_state->crtc_x < 0 || new_plane_state->crtc_y < 0
>>>> ||
>>>> @@ -558,7 +563,7 @@ static int
>>>> ingenic_ipu_plane_atomic_check(struct drm_plane *plane,
>>>> return -EINVAL;
>>>>
>>>> if (!osd_changed(new_plane_state, old_plane_state))
>>>> - return 0;
>>>> + goto out_check_damage;
>>>>
>>>> crtc_state->mode_changed = true;
>>>>
>>>> @@ -592,6 +597,9 @@ static int
>>>> ingenic_ipu_plane_atomic_check(struct drm_plane *plane,
>>>> ipu->denom_w = denom_w;
>>>> ipu->denom_h = denom_h;
>>>>
>>>> +out_check_damage:
>>>> + drm_atomic_helper_check_plane_damage(state, new_plane_state);
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>> @@ -773,6 +781,8 @@ static int ingenic_ipu_bind(struct device
>>>> *dev,
>>>> struct device *master, void *d)
>>>> return err;
>>>> }
>>>>
>>>> + drm_plane_enable_fb_damage_clips(plane);
>>>> +
>>>> /*
>>>> * Sharpness settings range is [0,32]
>>>> * 0 : nearest-neighbor
>>>> --
>>>> 2.30.1