[PATCH] drm/exynos/mixer: fix MIXER shadow registry synchronisation code
Marian Mihailescu
mihailescu2m at gmail.com
Fri Mar 8 00:12:36 UTC 2019
Tested on my Exynos5422 Odroid XU4, vsync seems to not happen at all,
screen remains black since kernel loads.
--
Either I've been missing something or nothing has been going on. (K. E. Gordon)
On Thu, Mar 7, 2019 at 1:36 AM Andrzej Hajda <a.hajda at samsung.com> wrote:
>
> MIXER on Exynos5 SoCs uses different synchronisation method than Exynos4
> to update internal state (shadow registers).
> Apparently the driver implements it incorrectly. The rule should be
> as follows:
> - do not request updating registers until previous request was finished,
> ie. MXR_CFG_LAYER_UPDATE_COUNT must be 0.
> - before setting registers synchronisation on VSYNC should be turned off,
> ie. MXR_STATUS_SYNC_ENABLE should be reset,
> - after finishing MXR_STATUS_SYNC_ENABLE should be set again.
> The patch hopefully implements it correctly.
> Below sample kernel log from page fault caused by the bug:
>
> [ 25.670038] exynos-sysmmu 14650000.sysmmu: 14450000.mixer: PAGE FAULT occurred at 0x2247b800
> [ 25.677888] ------------[ cut here ]------------
> [ 25.682164] kernel BUG at ../drivers/iommu/exynos-iommu.c:450!
> [ 25.687971] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
> [ 25.693778] Modules linked in:
> [ 25.696816] CPU: 5 PID: 1553 Comm: fb-release_test Not tainted 5.0.0-rc7-01157-g5f86b1566bdd #136
> [ 25.705646] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> [ 25.711710] PC is at exynos_sysmmu_irq+0x1c0/0x264
> [ 25.716470] LR is at lock_is_held_type+0x44/0x64
>
> Reported-by: Marian Mihailescu <mihailescu2m at gmail.com>
> Signed-off-by: Andrzej Hajda <a.hajda at samsung.com>
> ---
> drivers/gpu/drm/exynos/exynos_mixer.c | 107 +++++++++++++++-----------
> 1 file changed, 63 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
> index 0573eab0e190..42ce01c226ef 100644
> --- a/drivers/gpu/drm/exynos/exynos_mixer.c
> +++ b/drivers/gpu/drm/exynos/exynos_mixer.c
> @@ -20,6 +20,7 @@
> #include "regs-vp.h"
>
> #include <linux/kernel.h>
> +#include <linux/ktime.h>
> #include <linux/spinlock.h>
> #include <linux/wait.h>
> #include <linux/i2c.h>
> @@ -352,15 +353,59 @@ static void mixer_cfg_vp_blend(struct mixer_context *ctx, unsigned int alpha)
> mixer_reg_write(ctx, MXR_VIDEO_CFG, val);
> }
>
> -static void mixer_vsync_set_update(struct mixer_context *ctx, bool enable)
> +static bool mixer_is_synced(struct mixer_context *ctx)
> {
> - /* block update on vsync */
> - mixer_reg_writemask(ctx, MXR_STATUS, enable ?
> - MXR_STATUS_SYNC_ENABLE : 0, MXR_STATUS_SYNC_ENABLE);
> + u32 base, shadow;
>
> + if (ctx->mxr_ver == MXR_VER_16_0_33_0 ||
> + ctx->mxr_ver == MXR_VER_128_0_0_184)
> + return !(mixer_reg_read(ctx, MXR_CFG) &
> + MXR_CFG_LAYER_UPDATE_COUNT_MASK);
> +
> + if (test_bit(MXR_BIT_VP_ENABLED, &ctx->flags) &&
> + vp_reg_read(ctx, VP_SHADOW_UPDATE))
> + return false;
> +
> + base = mixer_reg_read(ctx, MXR_CFG);
> + shadow = mixer_reg_read(ctx, MXR_CFG_S);
> + if (base != shadow)
> + return false;
> +
> + base = mixer_reg_read(ctx, MXR_GRAPHIC_BASE(0));
> + shadow = mixer_reg_read(ctx, MXR_GRAPHIC_BASE_S(0));
> + if (base != shadow)
> + return false;
> +
> + base = mixer_reg_read(ctx, MXR_GRAPHIC_BASE(1));
> + shadow = mixer_reg_read(ctx, MXR_GRAPHIC_BASE_S(1));
> + if (base != shadow)
> + return false;
> +
> + return true;
> +}
> +
> +static int mixer_wait_for_sync(struct mixer_context *ctx)
> +{
> + ktime_t timeout = ktime_add_us(ktime_get(), 100000);
> +
> + while (!mixer_is_synced(ctx)) {
> + usleep_range(1000, 2000);
> + if (ktime_compare(ktime_get(), timeout) > 0)
> + return -ETIMEDOUT;
> + }
> + return 0;
> +}
> +
> +static void mixer_disable_sync(struct mixer_context *ctx)
> +{
> + mixer_reg_writemask(ctx, MXR_STATUS, 0, MXR_STATUS_SYNC_ENABLE);
> +}
> +
> +static void mixer_enable_sync(struct mixer_context *ctx)
> +{
> + mixer_reg_writemask(ctx, MXR_STATUS, ~0, MXR_STATUS_SYNC_ENABLE);
> if (test_bit(MXR_BIT_VP_ENABLED, &ctx->flags))
> - vp_reg_write(ctx, VP_SHADOW_UPDATE, enable ?
> - VP_SHADOW_UPDATE_ENABLE : 0);
> + vp_reg_write(ctx, VP_SHADOW_UPDATE, VP_SHADOW_UPDATE_ENABLE);
> }
>
> static void mixer_cfg_scan(struct mixer_context *ctx, int width, int height)
> @@ -498,7 +543,6 @@ static void vp_video_buffer(struct mixer_context *ctx,
>
> spin_lock_irqsave(&ctx->reg_slock, flags);
>
> - vp_reg_write(ctx, VP_SHADOW_UPDATE, 1);
> /* interlace or progressive scan mode */
> val = (test_bit(MXR_BIT_INTERLACE, &ctx->flags) ? ~0 : 0);
> vp_reg_writemask(ctx, VP_MODE, val, VP_MODE_LINE_SKIP);
> @@ -553,11 +597,6 @@ static void vp_video_buffer(struct mixer_context *ctx,
> vp_regs_dump(ctx);
> }
>
> -static void mixer_layer_update(struct mixer_context *ctx)
> -{
> - mixer_reg_writemask(ctx, MXR_CFG, ~0, MXR_CFG_LAYER_UPDATE);
> -}
> -
> static void mixer_graph_buffer(struct mixer_context *ctx,
> struct exynos_drm_plane *plane)
> {
> @@ -640,11 +679,6 @@ static void mixer_graph_buffer(struct mixer_context *ctx,
> mixer_cfg_layer(ctx, win, priority, true);
> mixer_cfg_gfx_blend(ctx, win, pixel_alpha, state->base.alpha);
>
> - /* layer update mandatory for mixer 16.0.33.0 */
> - if (ctx->mxr_ver == MXR_VER_16_0_33_0 ||
> - ctx->mxr_ver == MXR_VER_128_0_0_184)
> - mixer_layer_update(ctx);
> -
> spin_unlock_irqrestore(&ctx->reg_slock, flags);
>
> mixer_regs_dump(ctx);
> @@ -709,7 +743,7 @@ static void mixer_win_reset(struct mixer_context *ctx)
> static irqreturn_t mixer_irq_handler(int irq, void *arg)
> {
> struct mixer_context *ctx = arg;
> - u32 val, base, shadow;
> + u32 val;
>
> spin_lock(&ctx->reg_slock);
>
> @@ -723,26 +757,9 @@ static irqreturn_t mixer_irq_handler(int irq, void *arg)
> val &= ~MXR_INT_STATUS_VSYNC;
>
> /* interlace scan need to check shadow register */
> - if (test_bit(MXR_BIT_INTERLACE, &ctx->flags)) {
> - if (test_bit(MXR_BIT_VP_ENABLED, &ctx->flags) &&
> - vp_reg_read(ctx, VP_SHADOW_UPDATE))
> - goto out;
> -
> - base = mixer_reg_read(ctx, MXR_CFG);
> - shadow = mixer_reg_read(ctx, MXR_CFG_S);
> - if (base != shadow)
> - goto out;
> -
> - base = mixer_reg_read(ctx, MXR_GRAPHIC_BASE(0));
> - shadow = mixer_reg_read(ctx, MXR_GRAPHIC_BASE_S(0));
> - if (base != shadow)
> - goto out;
> -
> - base = mixer_reg_read(ctx, MXR_GRAPHIC_BASE(1));
> - shadow = mixer_reg_read(ctx, MXR_GRAPHIC_BASE_S(1));
> - if (base != shadow)
> - goto out;
> - }
> + if (test_bit(MXR_BIT_INTERLACE, &ctx->flags)
> + && !mixer_is_synced(ctx))
> + goto out;
>
> drm_crtc_handle_vblank(&ctx->crtc->base);
> }
> @@ -917,12 +934,14 @@ static void mixer_disable_vblank(struct exynos_drm_crtc *crtc)
>
> static void mixer_atomic_begin(struct exynos_drm_crtc *crtc)
> {
> - struct mixer_context *mixer_ctx = crtc->ctx;
> + struct mixer_context *ctx = crtc->ctx;
>
> - if (!test_bit(MXR_BIT_POWERED, &mixer_ctx->flags))
> + if (!test_bit(MXR_BIT_POWERED, &ctx->flags))
> return;
>
> - mixer_vsync_set_update(mixer_ctx, false);
> + if (mixer_wait_for_sync(ctx))
> + dev_err(ctx->dev, "timeout waiting for VSYNC\n");
> + mixer_disable_sync(ctx);
> }
>
> static void mixer_update_plane(struct exynos_drm_crtc *crtc,
> @@ -964,7 +983,7 @@ static void mixer_atomic_flush(struct exynos_drm_crtc *crtc)
> if (!test_bit(MXR_BIT_POWERED, &mixer_ctx->flags))
> return;
>
> - mixer_vsync_set_update(mixer_ctx, true);
> + mixer_enable_sync(mixer_ctx);
> exynos_crtc_handle_event(crtc);
> }
>
> @@ -979,7 +998,7 @@ static void mixer_enable(struct exynos_drm_crtc *crtc)
>
> exynos_drm_pipe_clk_enable(crtc, true);
>
> - mixer_vsync_set_update(ctx, false);
> + mixer_disable_sync(ctx);
>
> mixer_reg_writemask(ctx, MXR_STATUS, ~0, MXR_STATUS_SOFT_RESET);
>
> @@ -992,7 +1011,7 @@ static void mixer_enable(struct exynos_drm_crtc *crtc)
>
> mixer_commit(ctx);
>
> - mixer_vsync_set_update(ctx, true);
> + mixer_enable_sync(ctx);
>
> set_bit(MXR_BIT_POWERED, &ctx->flags);
> }
> --
> 2.17.1
>
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