Re: [PATCH v2] drm/exynos/mixer: fix MIXER shadow registry synchronisation code

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This patch works on my odroid xu4 too, on 5.0.3 kernel.

Thanks!
-Marian

> On 19 Mar 2019, at 11:35 pm, Andrzej Hajda <a.hajda@xxxxxxxxxxx> 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
> 
> v2: added missing MXR_CFG_LAYER_UPDATE bit setting in mixer_enable_sync
> 
> Reported-by: Marian Mihailescu <mihailescu2m@xxxxxxxxx>
> Signed-off-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> ---
> Hi Inki and Marian,
> 
> This is fixed version of my previous patch. The only difference is
> added missing MXR_CFG_LAYER_UPDATE setting in mixer_enable_sync.
> I hope this time it is correct. It should solve one page fault issue
> in MIXER, Marek is preparing fix for another issue (to low clock set by
> devfreq). I hope with both patches page faults will not happen anymore ;)
> 
> Regards
> Andrzej
> ---
> drivers/gpu/drm/exynos/exynos_mixer.c | 110 +++++++++++++++-----------
> 1 file changed, 66 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/gpu/drm/exynos/exynos_mixer.c b/drivers/gpu/drm/exynos/exynos_mixer.c
> index 0573eab0e190..f35e4ab55b27 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 +353,62 @@ 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)
> +{
> +    if (ctx->mxr_ver == MXR_VER_16_0_33_0 ||
> +        ctx->mxr_ver == MXR_VER_128_0_0_184)
> +        mixer_reg_writemask(ctx, MXR_CFG, ~0, MXR_CFG_LAYER_UPDATE);
> +    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 +546,6 @@ 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 +600,6 @@ 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 +682,6 @@ 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 +746,7 @@ 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 +760,9 @@ 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 +937,14 @@ 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 +986,7 @@ 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 +1001,7 @@ 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 +1014,7 @@ 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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