Re: [PATCH V3 2/5] drm/vkms: Rename vkms_crc.c into vkms_composer.c
From: Daniel Vetter
Date: Thu Jul 11 2019 - 04:10:33 EST
On Tue, Jun 25, 2019 at 10:37:05PM -0300, Rodrigo Siqueira wrote:
> As a preparation work for introducing writeback to vkms, this patch
> renames the file vkms_crc.c into vkms_composer.c. Accordingly, it also
> adjusts the functions and data structures to match the changes.
>
> No functional change.
>
> Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Too lazy to check it still compiles :-)
-Daniel
> ---
> drivers/gpu/drm/vkms/Makefile | 2 +-
> .../drm/vkms/{vkms_crc.c => vkms_composer.c} | 98 ++++++++++---------
> drivers/gpu/drm/vkms/vkms_crtc.c | 30 +++---
> drivers/gpu/drm/vkms/vkms_drv.c | 4 +-
> drivers/gpu/drm/vkms/vkms_drv.h | 28 +++---
> drivers/gpu/drm/vkms/vkms_plane.c | 36 +++----
> 6 files changed, 101 insertions(+), 97 deletions(-)
> rename drivers/gpu/drm/vkms/{vkms_crc.c => vkms_composer.c} (65%)
>
> diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> index 89f09bec7b23..0b767d7efa24 100644
> --- a/drivers/gpu/drm/vkms/Makefile
> +++ b/drivers/gpu/drm/vkms/Makefile
> @@ -1,4 +1,4 @@
> # SPDX-License-Identifier: GPL-2.0-only
> -vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_crc.o
> +vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_composer.o
>
> obj-$(CONFIG_DRM_VKMS) += vkms.o
> diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_composer.c
> similarity index 65%
> rename from drivers/gpu/drm/vkms/vkms_crc.c
> rename to drivers/gpu/drm/vkms/vkms_composer.c
> index 30b048b67a32..eb7ea8be1f98 100644
> --- a/drivers/gpu/drm/vkms/vkms_crc.c
> +++ b/drivers/gpu/drm/vkms/vkms_composer.c
> @@ -10,25 +10,25 @@
> * compute_crc - Compute CRC value on output frame
> *
> * @vaddr_out: address to final framebuffer
> - * @crc_out: framebuffer's metadata
> + * @composer: framebuffer's metadata
> *
> * returns CRC value computed using crc32 on the visible portion of
> * the final framebuffer at vaddr_out
> */
> -static uint32_t compute_crc(void *vaddr_out, struct vkms_crc_data *crc_out)
> +static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer)
> {
> int i, j, src_offset;
> - int x_src = crc_out->src.x1 >> 16;
> - int y_src = crc_out->src.y1 >> 16;
> - int h_src = drm_rect_height(&crc_out->src) >> 16;
> - int w_src = drm_rect_width(&crc_out->src) >> 16;
> + int x_src = composer->src.x1 >> 16;
> + int y_src = composer->src.y1 >> 16;
> + int h_src = drm_rect_height(&composer->src) >> 16;
> + int w_src = drm_rect_width(&composer->src) >> 16;
> u32 crc = 0;
>
> for (i = y_src; i < y_src + h_src; ++i) {
> for (j = x_src; j < x_src + w_src; ++j) {
> - src_offset = crc_out->offset
> - + (i * crc_out->pitch)
> - + (j * crc_out->cpp);
> + src_offset = composer->offset
> + + (i * composer->pitch)
> + + (j * composer->cpp);
> /* XRGB format ignores Alpha channel */
> memset(vaddr_out + src_offset + 24, 0, 8);
> crc = crc32_le(crc, vaddr_out + src_offset,
> @@ -43,8 +43,8 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_crc_data *crc_out)
> * blend - belnd value at vaddr_src with value at vaddr_dst
> * @vaddr_dst: destination address
> * @vaddr_src: source address
> - * @crc_dst: destination framebuffer's metadata
> - * @crc_src: source framebuffer's metadata
> + * @dest_composer: destination framebuffer's metadata
> + * @src_composer: source framebuffer's metadata
> *
> * Blend value at vaddr_src with value at vaddr_dst.
> * Currently, this function write value at vaddr_src on value
> @@ -55,31 +55,31 @@ static uint32_t compute_crc(void *vaddr_out, struct vkms_crc_data *crc_out)
> * instead of overwriting it.
> */
> static void blend(void *vaddr_dst, void *vaddr_src,
> - struct vkms_crc_data *crc_dst,
> - struct vkms_crc_data *crc_src)
> + struct vkms_composer *dest_composer,
> + struct vkms_composer *src_composer)
> {
> int i, j, j_dst, i_dst;
> int offset_src, offset_dst;
>
> - int x_src = crc_src->src.x1 >> 16;
> - int y_src = crc_src->src.y1 >> 16;
> + int x_src = src_composer->src.x1 >> 16;
> + int y_src = src_composer->src.y1 >> 16;
>
> - int x_dst = crc_src->dst.x1;
> - int y_dst = crc_src->dst.y1;
> - int h_dst = drm_rect_height(&crc_src->dst);
> - int w_dst = drm_rect_width(&crc_src->dst);
> + int x_dst = src_composer->dst.x1;
> + int y_dst = src_composer->dst.y1;
> + int h_dst = drm_rect_height(&src_composer->dst);
> + int w_dst = drm_rect_width(&src_composer->dst);
>
> int y_limit = y_src + h_dst;
> int x_limit = x_src + w_dst;
>
> for (i = y_src, i_dst = y_dst; i < y_limit; ++i) {
> for (j = x_src, j_dst = x_dst; j < x_limit; ++j) {
> - offset_dst = crc_dst->offset
> - + (i_dst * crc_dst->pitch)
> - + (j_dst++ * crc_dst->cpp);
> - offset_src = crc_src->offset
> - + (i * crc_src->pitch)
> - + (j * crc_src->cpp);
> + offset_dst = dest_composer->offset
> + + (i_dst * dest_composer->pitch)
> + + (j_dst++ * dest_composer->cpp);
> + offset_src = src_composer->offset
> + + (i * src_composer->pitch)
> + + (j * src_composer->cpp);
>
> memcpy(vaddr_dst + offset_dst,
> vaddr_src + offset_src, sizeof(u32));
> @@ -88,25 +88,27 @@ static void blend(void *vaddr_dst, void *vaddr_src,
> }
> }
>
> -static void compose_cursor(struct vkms_crc_data *cursor_crc,
> - struct vkms_crc_data *primary_crc, void *vaddr_out)
> +static void compose_cursor(struct vkms_composer *cursor_composer,
> + struct vkms_composer *primary_composer,
> + void *vaddr_out)
> {
> struct drm_gem_object *cursor_obj;
> struct vkms_gem_object *cursor_vkms_obj;
>
> - cursor_obj = drm_gem_fb_get_obj(&cursor_crc->fb, 0);
> + cursor_obj = drm_gem_fb_get_obj(&cursor_composer->fb, 0);
> cursor_vkms_obj = drm_gem_to_vkms_gem(cursor_obj);
>
> if (WARN_ON(!cursor_vkms_obj->vaddr))
> return;
>
> - blend(vaddr_out, cursor_vkms_obj->vaddr, primary_crc, cursor_crc);
> + blend(vaddr_out, cursor_vkms_obj->vaddr,
> + primary_composer, cursor_composer);
> }
>
> -static uint32_t _vkms_get_crc(struct vkms_crc_data *primary_crc,
> - struct vkms_crc_data *cursor_crc)
> +static uint32_t _vkms_get_crc(struct vkms_composer *primary_composer,
> + struct vkms_composer *cursor_composer)
> {
> - struct drm_framebuffer *fb = &primary_crc->fb;
> + struct drm_framebuffer *fb = &primary_composer->fb;
> struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
> struct vkms_gem_object *vkms_obj = drm_gem_to_vkms_gem(gem_obj);
> void *vaddr_out = kzalloc(vkms_obj->gem.size, GFP_KERNEL);
> @@ -124,10 +126,10 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *primary_crc,
>
> memcpy(vaddr_out, vkms_obj->vaddr, vkms_obj->gem.size);
>
> - if (cursor_crc)
> - compose_cursor(cursor_crc, primary_crc, vaddr_out);
> + if (cursor_composer)
> + compose_cursor(cursor_composer, primary_composer, vaddr_out);
>
> - crc = compute_crc(vaddr_out, primary_crc);
> + crc = compute_crc(vaddr_out, primary_composer);
>
> kfree(vaddr_out);
>
> @@ -135,35 +137,35 @@ static uint32_t _vkms_get_crc(struct vkms_crc_data *primary_crc,
> }
>
> /**
> - * vkms_crc_work_handle - ordered work_struct to compute CRC
> + * vkms_composer_worker - ordered work_struct to compute CRC
> *
> * @work: work_struct
> *
> - * Work handler for computing CRCs. work_struct scheduled in
> + * Work handler for composing and computing CRCs. work_struct scheduled in
> * an ordered workqueue that's periodically scheduled to run by
> * _vblank_handle() and flushed at vkms_atomic_crtc_destroy_state().
> */
> -void vkms_crc_work_handle(struct work_struct *work)
> +void vkms_composer_worker(struct work_struct *work)
> {
> struct vkms_crtc_state *crtc_state = container_of(work,
> struct vkms_crtc_state,
> - crc_work);
> + composer_work);
> struct drm_crtc *crtc = crtc_state->base.crtc;
> struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> - struct vkms_crc_data *primary_crc = NULL;
> - struct vkms_crc_data *cursor_crc = NULL;
> + struct vkms_composer *primary_composer = NULL;
> + struct vkms_composer *cursor_composer = NULL;
> u32 crc32 = 0;
> u64 frame_start, frame_end;
> bool crc_pending;
>
> - spin_lock_irq(&out->crc_lock);
> + spin_lock_irq(&out->composer_lock);
> frame_start = crtc_state->frame_start;
> frame_end = crtc_state->frame_end;
> crc_pending = crtc_state->crc_pending;
> crtc_state->frame_start = 0;
> crtc_state->frame_end = 0;
> crtc_state->crc_pending = false;
> - spin_unlock_irq(&out->crc_lock);
> + spin_unlock_irq(&out->composer_lock);
>
> /*
> * We raced with the vblank hrtimer and previous work already computed
> @@ -173,13 +175,13 @@ void vkms_crc_work_handle(struct work_struct *work)
> return;
>
> if (crtc_state->num_active_planes >= 1)
> - primary_crc = crtc_state->active_planes[0]->crc_data;
> + primary_composer = crtc_state->active_planes[0]->composer;
>
> if (crtc_state->num_active_planes == 2)
> - cursor_crc = crtc_state->active_planes[1]->crc_data;
> + cursor_composer = crtc_state->active_planes[1]->composer;
>
> - if (primary_crc)
> - crc32 = _vkms_get_crc(primary_crc, cursor_crc);
> + if (primary_composer)
> + crc32 = _vkms_get_crc(primary_composer, cursor_composer);
>
> /*
> * The worker can fall behind the vblank hrtimer, make sure we catch up.
> @@ -237,7 +239,7 @@ int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name)
> ret = vkms_crc_parse_source(src_name, &enabled);
>
> spin_lock_irq(&out->lock);
> - out->crc_enabled = enabled;
> + out->composer_enabled = enabled;
> spin_unlock_irq(&out->lock);
>
> return ret;
> diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> index a648892379c3..04c6f4250dea 100644
> --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> @@ -24,14 +24,14 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
> if (!ret)
> DRM_ERROR("vkms failure on handling vblank");
>
> - state = output->crc_state;
> - if (state && output->crc_enabled) {
> + state = output->composer_state;
> + if (state && output->composer_enabled) {
> u64 frame = drm_crtc_accurate_vblank_count(crtc);
>
> - /* update frame_start only if a queued vkms_crc_work_handle()
> + /* update frame_start only if a queued vkms_composer_worker()
> * has read the data
> */
> - spin_lock(&output->crc_lock);
> + spin_lock(&output->composer_lock);
> if (!state->crc_pending)
> state->frame_start = frame;
> else
> @@ -39,11 +39,11 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
> state->frame_start, frame);
> state->frame_end = frame;
> state->crc_pending = true;
> - spin_unlock(&output->crc_lock);
> + spin_unlock(&output->composer_lock);
>
> - ret = queue_work(output->crc_workq, &state->crc_work);
> + ret = queue_work(output->composer_workq, &state->composer_work);
> if (!ret)
> - DRM_DEBUG_DRIVER("vkms_crc_work_handle already queued\n");
> + DRM_DEBUG_DRIVER("Composer worker already queued\n");
> }
>
> spin_unlock(&output->lock);
> @@ -114,7 +114,7 @@ vkms_atomic_crtc_duplicate_state(struct drm_crtc *crtc)
>
> __drm_atomic_helper_crtc_duplicate_state(crtc, &vkms_state->base);
>
> - INIT_WORK(&vkms_state->crc_work, vkms_crc_work_handle);
> + INIT_WORK(&vkms_state->composer_work, vkms_composer_worker);
>
> return &vkms_state->base;
> }
> @@ -126,7 +126,7 @@ static void vkms_atomic_crtc_destroy_state(struct drm_crtc *crtc,
>
> __drm_atomic_helper_crtc_destroy_state(state);
>
> - WARN_ON(work_pending(&vkms_state->crc_work));
> + WARN_ON(work_pending(&vkms_state->composer_work));
> kfree(vkms_state->active_planes);
> kfree(vkms_state);
> }
> @@ -141,7 +141,7 @@ static void vkms_atomic_crtc_reset(struct drm_crtc *crtc)
>
> __drm_atomic_helper_crtc_reset(crtc, &vkms_state->base);
> if (vkms_state)
> - INIT_WORK(&vkms_state->crc_work, vkms_crc_work_handle);
> + INIT_WORK(&vkms_state->composer_work, vkms_composer_worker);
> }
>
> static const struct drm_crtc_funcs vkms_crtc_funcs = {
> @@ -222,7 +222,7 @@ static void vkms_crtc_atomic_begin(struct drm_crtc *crtc,
> struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
>
> /* This lock is held across the atomic commit to block vblank timer
> - * from scheduling vkms_crc_work_handle until the crc_data is updated
> + * from scheduling vkms_composer_worker until the composer is updated
> */
> spin_lock_irq(&vkms_output->lock);
> }
> @@ -245,7 +245,7 @@ static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
> crtc->state->event = NULL;
> }
>
> - vkms_output->crc_state = to_vkms_crtc_state(crtc->state);
> + vkms_output->composer_state = to_vkms_crtc_state(crtc->state);
>
> spin_unlock_irq(&vkms_output->lock);
> }
> @@ -274,10 +274,10 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
> drm_crtc_helper_add(crtc, &vkms_crtc_helper_funcs);
>
> spin_lock_init(&vkms_out->lock);
> - spin_lock_init(&vkms_out->crc_lock);
> + spin_lock_init(&vkms_out->composer_lock);
>
> - vkms_out->crc_workq = alloc_ordered_workqueue("vkms_crc_workq", 0);
> - if (!vkms_out->crc_workq)
> + vkms_out->composer_workq = alloc_ordered_workqueue("vkms_composer", 0);
> + if (!vkms_out->composer_workq)
> return -ENOMEM;
>
> return ret;
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> index 966b3d653189..ac790b6527e4 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.c
> +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> @@ -56,7 +56,7 @@ static void vkms_release(struct drm_device *dev)
> drm_atomic_helper_shutdown(&vkms->drm);
> drm_mode_config_cleanup(&vkms->drm);
> drm_dev_fini(&vkms->drm);
> - destroy_workqueue(vkms->output.crc_workq);
> + destroy_workqueue(vkms->output.composer_workq);
> }
>
> static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)
> @@ -82,7 +82,7 @@ static void vkms_atomic_commit_tail(struct drm_atomic_state *old_state)
> struct vkms_crtc_state *vkms_state =
> to_vkms_crtc_state(old_crtc_state);
>
> - flush_work(&vkms_state->crc_work);
> + flush_work(&vkms_state->composer_work);
> }
>
> drm_atomic_helper_cleanup_planes(dev, old_state);
> diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> index e2d1aa089dec..fc6cda164336 100644
> --- a/drivers/gpu/drm/vkms/vkms_drv.h
> +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> @@ -20,7 +20,7 @@
>
> extern bool enable_cursor;
>
> -struct vkms_crc_data {
> +struct vkms_composer {
> struct drm_framebuffer fb;
> struct drm_rect src, dst;
> unsigned int offset;
> @@ -31,29 +31,29 @@ struct vkms_crc_data {
> /**
> * vkms_plane_state - Driver specific plane state
> * @base: base plane state
> - * @crc_data: data required for CRC computation
> + * @composer: data required for composing computation
> */
> struct vkms_plane_state {
> struct drm_plane_state base;
> - struct vkms_crc_data *crc_data;
> + struct vkms_composer *composer;
> };
>
> /**
> * vkms_crtc_state - Driver specific CRTC state
> * @base: base CRTC state
> - * @crc_work: work struct to compute and add CRC entries
> + * @composer_work: work struct to compose and add CRC entries
> * @n_frame_start: start frame number for computed CRC
> * @n_frame_end: end frame number for computed CRC
> */
> struct vkms_crtc_state {
> struct drm_crtc_state base;
> - struct work_struct crc_work;
> + struct work_struct composer_work;
>
> int num_active_planes;
> /* stack of active planes for crc computation, should be in z order */
> struct vkms_plane_state **active_planes;
>
> - /* below three are protected by vkms_output.crc_lock */
> + /* below three are protected by vkms_output.composer_lock */
> bool crc_pending;
> u64 frame_start;
> u64 frame_end;
> @@ -66,16 +66,16 @@ struct vkms_output {
> struct hrtimer vblank_hrtimer;
> ktime_t period_ns;
> struct drm_pending_vblank_event *event;
> - /* ordered wq for crc_work */
> - struct workqueue_struct *crc_workq;
> - /* protects concurrent access to crc_data */
> + /* ordered wq for composer_work */
> + struct workqueue_struct *composer_workq;
> + /* protects concurrent access to composer */
> spinlock_t lock;
>
> /* protected by @lock */
> - bool crc_enabled;
> - struct vkms_crtc_state *crc_state;
> + bool composer_enabled;
> + struct vkms_crtc_state *composer_state;
>
> - spinlock_t crc_lock;
> + spinlock_t composer_lock;
> };
>
> struct vkms_device {
> @@ -143,6 +143,8 @@ const char *const *vkms_get_crc_sources(struct drm_crtc *crtc,
> int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name);
> int vkms_verify_crc_source(struct drm_crtc *crtc, const char *source_name,
> size_t *values_cnt);
> -void vkms_crc_work_handle(struct work_struct *work);
> +
> +/* Composer Support */
> +void vkms_composer_worker(struct work_struct *work);
>
> #endif /* _VKMS_DRV_H_ */
> diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> index 18c630cfc485..8b60d3434d75 100644
> --- a/drivers/gpu/drm/vkms/vkms_plane.c
> +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> @@ -18,20 +18,20 @@ static struct drm_plane_state *
> vkms_plane_duplicate_state(struct drm_plane *plane)
> {
> struct vkms_plane_state *vkms_state;
> - struct vkms_crc_data *crc_data;
> + struct vkms_composer *composer;
>
> vkms_state = kzalloc(sizeof(*vkms_state), GFP_KERNEL);
> if (!vkms_state)
> return NULL;
>
> - crc_data = kzalloc(sizeof(*crc_data), GFP_KERNEL);
> - if (!crc_data) {
> - DRM_DEBUG_KMS("Couldn't allocate crc_data\n");
> + composer = kzalloc(sizeof(*composer), GFP_KERNEL);
> + if (!composer) {
> + DRM_DEBUG_KMS("Couldn't allocate composer\n");
> kfree(vkms_state);
> return NULL;
> }
>
> - vkms_state->crc_data = crc_data;
> + vkms_state->composer = composer;
>
> __drm_atomic_helper_plane_duplicate_state(plane,
> &vkms_state->base);
> @@ -49,12 +49,12 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
> /* dropping the reference we acquired in
> * vkms_primary_plane_update()
> */
> - if (drm_framebuffer_read_refcount(&vkms_state->crc_data->fb))
> - drm_framebuffer_put(&vkms_state->crc_data->fb);
> + if (drm_framebuffer_read_refcount(&vkms_state->composer->fb))
> + drm_framebuffer_put(&vkms_state->composer->fb);
> }
>
> - kfree(vkms_state->crc_data);
> - vkms_state->crc_data = NULL;
> + kfree(vkms_state->composer);
> + vkms_state->composer = NULL;
>
> __drm_atomic_helper_plane_destroy_state(old_state);
> kfree(vkms_state);
> @@ -91,21 +91,21 @@ static void vkms_plane_atomic_update(struct drm_plane *plane,
> {
> struct vkms_plane_state *vkms_plane_state;
> struct drm_framebuffer *fb = plane->state->fb;
> - struct vkms_crc_data *crc_data;
> + struct vkms_composer *composer;
>
> if (!plane->state->crtc || !fb)
> return;
>
> vkms_plane_state = to_vkms_plane_state(plane->state);
>
> - crc_data = vkms_plane_state->crc_data;
> - memcpy(&crc_data->src, &plane->state->src, sizeof(struct drm_rect));
> - memcpy(&crc_data->dst, &plane->state->dst, sizeof(struct drm_rect));
> - memcpy(&crc_data->fb, fb, sizeof(struct drm_framebuffer));
> - drm_framebuffer_get(&crc_data->fb);
> - crc_data->offset = fb->offsets[0];
> - crc_data->pitch = fb->pitches[0];
> - crc_data->cpp = fb->format->cpp[0];
> + composer = vkms_plane_state->composer;
> + memcpy(&composer->src, &plane->state->src, sizeof(struct drm_rect));
> + memcpy(&composer->dst, &plane->state->dst, sizeof(struct drm_rect));
> + memcpy(&composer->fb, fb, sizeof(struct drm_framebuffer));
> + drm_framebuffer_get(&composer->fb);
> + composer->offset = fb->offsets[0];
> + composer->pitch = fb->pitches[0];
> + composer->cpp = fb->format->cpp[0];
> }
>
> static int vkms_plane_atomic_check(struct drm_plane *plane,
> --
> 2.21.0
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch