[PATCH v3 1/1] drm/mediatek: Filter modes according to hardware capability
CK Hu (胡俊光)
ck.hu at mediatek.com
Thu Feb 22 21:50:23 PST 2024
Hi, Shawn:
On Tue, 2024-02-20 at 17:37 +0800, Shawn Sung wrote:
> From: Hsiao Chien Sung <shawn.sung at mediatek.corp-partner.google.com>
>
> We found a stability issue on MT8188 when connecting an external
> monitor
> in 2560x1440 at 144Hz mode. Checked with the designer, there is a
> function
> called "prefetch" which is working during VBP (triggered by VSYNC).
> If the duration of VBP is too short, the throughput requirement could
> increase more than 3 times and lead to stability issues.
>
> The mode settings that VDOSYS supports are mainly affected by clock
> rate and throughput, display driver should filter these settings
> according to the SoC's limitation to avoid unstable conditions.
>
> Since currently the mode filter is only available on MT8195 and
> MT8188
> and they share the same compatible name, the reference number (8250)
> is hard coded instead of in the driver data.
Reviewed-by: CK Hu <ck.hu at mediatek.com>
>
> Signed-off-by: Hsiao Chien Sung <
> shawn.sung at mediatek.corp-partner.google.com>
> ---
> drivers/gpu/drm/mediatek/mtk_disp_drv.h | 4 ++
> drivers/gpu/drm/mediatek/mtk_disp_merge.c | 65
> +++++++++++++++++++
> .../gpu/drm/mediatek/mtk_disp_ovl_adaptor.c | 17 +++++
> drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 17 +++++
> drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c | 1 +
> drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h | 12 ++++
> 6 files changed, 116 insertions(+)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> b/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> index eb738f14f09e3..4a5661334fb1a 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> @@ -72,6 +72,8 @@ void mtk_merge_advance_config(struct device *dev,
> unsigned int l_w, unsigned int
> struct cmdq_pkt *cmdq_pkt);
> void mtk_merge_start_cmdq(struct device *dev, struct cmdq_pkt
> *cmdq_pkt);
> void mtk_merge_stop_cmdq(struct device *dev, struct cmdq_pkt
> *cmdq_pkt);
> +enum drm_mode_status mtk_merge_mode_valid(struct device *dev,
> + const struct drm_display_mode
> *mode);
>
> void mtk_ovl_bgclr_in_on(struct device *dev);
> void mtk_ovl_bgclr_in_off(struct device *dev);
> @@ -130,6 +132,8 @@ unsigned int mtk_ovl_adaptor_layer_nr(struct
> device *dev);
> struct device *mtk_ovl_adaptor_dma_dev_get(struct device *dev);
> const u32 *mtk_ovl_adaptor_get_formats(struct device *dev);
> size_t mtk_ovl_adaptor_get_num_formats(struct device *dev);
> +enum drm_mode_status mtk_ovl_adaptor_mode_valid(struct device *dev,
> + const struct
> drm_display_mode *mode);
>
> void mtk_rdma_bypass_shadow(struct device *dev);
> int mtk_rdma_clk_enable(struct device *dev);
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_merge.c
> b/drivers/gpu/drm/mediatek/mtk_disp_merge.c
> index c19fb1836034d..80953b3e8ace6 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_merge.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_merge.c
> @@ -223,6 +223,71 @@ void mtk_merge_clk_disable(struct device *dev)
> clk_disable_unprepare(priv->clk);
> }
>
> +enum drm_mode_status mtk_merge_mode_valid(struct device *dev,
> + const struct drm_display_mode
> *mode)
> +{
> + struct mtk_disp_merge *priv = dev_get_drvdata(dev);
> + unsigned long rate = 0;
> +
> + rate = clk_get_rate(priv->clk);
> +
> + /* Convert to KHz and round the number */
> + rate = (rate + 500) / 1000;
> +
> + if (rate && mode->clock > rate) {
> + dev_dbg(dev, "invalid clock: %d (>%lu)\n", mode->clock,
> rate);
> + return MODE_CLOCK_HIGH;
> + }
> +
> + /*
> + * Measure the bandwidth requirement of hardware prefetch (per
> frame)
> + *
> + * let N = prefetch buffer size in lines
> + * (ex. N=3, then prefetch buffer size = 3 lines)
> + *
> + * prefetch size = htotal * N (pixels)
> + * time per line = 1 / fps / vtotal (seconds)
> + * duration = vbp * time per line
> + * = vbp / fps / vtotal
> + *
> + * data rate = prefetch size / duration
> + * = htotal * N / (vbp / fps / vtotal)
> + * = htotal * vtotal * fps * N / vbp
> + * = clk * N / vbp (pixels per second)
> + *
> + * Say 4K60 (CEA-861) is the maximum mode supported by the SoC
> + * data rate = 594000K * N / 72 = 8250 (standard)
> + * (remove K * N due to the same unit)
> + *
> + * For 2560x1440 at 144 (clk=583600K, vbp=17):
> + * data rate = 583600 / 17 ~= 34329 > 8250 (NG)
> + *
> + * For 2560x1440 at 120 (clk=497760K, vbp=77):
> + * data rate = 497760 / 77 ~= 6464 < 8250 (OK)
> + *
> + * A non-standard 4K60 timing (clk=521280K, vbp=54)
> + * data rate = 521280 / 54 ~= 9653 > 8250 (NG)
> + *
> + * Bandwidth requirement of hardware prefetch increases
> significantly
> + * when the VBP decreases (more than 4x in this example).
> + *
> + * The proposed formula is only one way to estimate whether our
> SoC
> + * supports the mode setting. The basic idea behind it is just
> to check
> + * if the data rate requirement is too high (directly
> proportional to
> + * pixel clock, inversely proportional to vbp). Please adjust
> the
> + * function if it doesn't fit your situation in the future.
> + */
> + rate = mode->clock / (mode->vtotal - mode->vsync_end);
> +
> + if (rate > 8250) {
> + dev_dbg(dev, "invalid rate: %lu (>8250): " DRM_MODE_FMT
> "\n",
> + rate, DRM_MODE_ARG(mode));
> + return MODE_BAD;
> + }
> +
> + return MODE_OK;
> +}
> +
> static int mtk_disp_merge_bind(struct device *dev, struct device
> *master,
> void *data)
> {
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c
> b/drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c
> index 10d23e76acaa9..6d4334955e3d3 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl_adaptor.c
> @@ -88,6 +88,7 @@ static const struct mtk_ddp_comp_funcs ethdr = {
> static const struct mtk_ddp_comp_funcs merge = {
> .clk_enable = mtk_merge_clk_enable,
> .clk_disable = mtk_merge_clk_disable,
> + .mode_valid = mtk_merge_mode_valid,
> };
>
> static const struct mtk_ddp_comp_funcs padding = {
> @@ -341,6 +342,22 @@ void mtk_ovl_adaptor_clk_disable(struct device
> *dev)
> }
> }
>
> +enum drm_mode_status mtk_ovl_adaptor_mode_valid(struct device *dev,
> + const struct
> drm_display_mode *mode)
> +
> +{
> + int i;
> + struct mtk_disp_ovl_adaptor *ovl_adaptor =
> dev_get_drvdata(dev);
> +
> + for (i = 0; i < OVL_ADAPTOR_ID_MAX; i++) {
> + dev = ovl_adaptor->ovl_adaptor_comp[i];
> + if (!dev || !comp_matches[i].funcs->mode_valid)
> + continue;
> + return comp_matches[i].funcs->mode_valid(dev, mode);
> + }
> + return MODE_OK;
> +}
> +
> unsigned int mtk_ovl_adaptor_layer_nr(struct device *dev)
> {
> return MTK_OVL_ADAPTOR_LAYER_NUM;
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index 1dac8d0fbc669..14cf75fa217f9 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -212,6 +212,22 @@ static void mtk_drm_crtc_destroy_state(struct
> drm_crtc *crtc,
> kfree(to_mtk_crtc_state(state));
> }
>
> +static enum drm_mode_status
> +mtk_drm_crtc_mode_valid(struct drm_crtc *crtc,
> + const struct drm_display_mode *mode)
> +{
> + struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> + enum drm_mode_status status = MODE_OK;
> + int i;
> +
> + for (i = 0; i < mtk_crtc->ddp_comp_nr; i++) {
> + status = mtk_ddp_comp_mode_valid(mtk_crtc->ddp_comp[i],
> mode);
> + if (status != MODE_OK)
> + break;
> + }
> + return status;
> +}
> +
> static bool mtk_drm_crtc_mode_fixup(struct drm_crtc *crtc,
> const struct drm_display_mode
> *mode,
> struct drm_display_mode
> *adjusted_mode)
> @@ -830,6 +846,7 @@ static const struct drm_crtc_funcs mtk_crtc_funcs
> = {
> static const struct drm_crtc_helper_funcs mtk_crtc_helper_funcs = {
> .mode_fixup = mtk_drm_crtc_mode_fixup,
> .mode_set_nofb = mtk_drm_crtc_mode_set_nofb,
> + .mode_valid = mtk_drm_crtc_mode_valid,
> .atomic_begin = mtk_drm_crtc_atomic_begin,
> .atomic_flush = mtk_drm_crtc_atomic_flush,
> .atomic_enable = mtk_drm_crtc_atomic_enable,
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> index 9633e860cc3ce..94590227c56a9 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.c
> @@ -416,6 +416,7 @@ static const struct mtk_ddp_comp_funcs
> ddp_ovl_adaptor = {
> .remove = mtk_ovl_adaptor_remove_comp,
> .get_formats = mtk_ovl_adaptor_get_formats,
> .get_num_formats = mtk_ovl_adaptor_get_num_formats,
> + .mode_valid = mtk_ovl_adaptor_mode_valid,
> };
>
> static const char * const mtk_ddp_comp_stem[MTK_DDP_COMP_TYPE_MAX] =
> {
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> index f8c7e8d8ddc12..215b7234ff13c 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_ddp_comp.h
> @@ -12,6 +12,8 @@
> #include <linux/soc/mediatek/mtk-mmsys.h>
> #include <linux/soc/mediatek/mtk-mutex.h>
>
> +#include <drm/drm_modes.h>
> +
> struct device;
> struct device_node;
> struct drm_crtc;
> @@ -84,6 +86,7 @@ struct mtk_ddp_comp_funcs {
> void (*add)(struct device *dev, struct mtk_mutex *mutex);
> void (*remove)(struct device *dev, struct mtk_mutex *mutex);
> unsigned int (*encoder_index)(struct device *dev);
> + enum drm_mode_status (*mode_valid)(struct device *dev, const
> struct drm_display_mode *mode);
> };
>
> struct mtk_ddp_comp {
> @@ -125,6 +128,15 @@ static inline void
> mtk_ddp_comp_clk_disable(struct mtk_ddp_comp *comp)
> comp->funcs->clk_disable(comp->dev);
> }
>
> +static inline
> +enum drm_mode_status mtk_ddp_comp_mode_valid(struct mtk_ddp_comp
> *comp,
> + const struct
> drm_display_mode *mode)
> +{
> + if (comp && comp->funcs && comp->funcs->mode_valid)
> + return comp->funcs->mode_valid(comp->dev, mode);
> + return MODE_OK;
> +}
> +
> static inline void mtk_ddp_comp_config(struct mtk_ddp_comp *comp,
> unsigned int w, unsigned int h,
> unsigned int vrefresh, unsigned
> int bpc,
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