Re: [PATCH] drm/stm: ltdc: update hardware error management

[Philippe CORNU]

On 6/3/22 15:46, Yannick Fertre wrote:
> The latest hardware version (0x40100) supports a hardware threshold
> register (aka FUTR) to trigger a fifo underrun interrupt.
> A software threshold has been implemented for other hardware versions.
> The threshold is set to 128 by default.
>
> Signed-off-by: Yannick Fertre <yannick.fertre@xxxxxxxxxxx>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 90 ++++++++++++++++++++++++++++++--------
>   drivers/gpu/drm/stm/ltdc.h |  6 ++-
>   2 files changed, 77 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index ff2075dd9474..42a3bd515477 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -162,16 +162,20 @@
>   #define BCCR_BCWHITE	GENMASK(23, 0)	/* Background Color WHITE */
>   
>   #define IER_LIE		BIT(0)		/* Line Interrupt Enable */
> -#define IER_FUIE	BIT(1)		/* Fifo Underrun Interrupt Enable */
> +#define IER_FUWIE	BIT(1)		/* Fifo Underrun Warning Interrupt Enable */
>   #define IER_TERRIE	BIT(2)		/* Transfer ERRor Interrupt Enable */
> -#define IER_RRIE	BIT(3)		/* Register Reload Interrupt enable */
> +#define IER_RRIE	BIT(3)		/* Register Reload Interrupt Enable */
> +#define IER_FUEIE	BIT(6)		/* Fifo Underrun Error Interrupt Enable */
> +#define IER_CRCIE	BIT(7)		/* CRC Error Interrupt Enable */
>   
>   #define CPSR_CYPOS	GENMASK(15, 0)	/* Current Y position */
>   
>   #define ISR_LIF		BIT(0)		/* Line Interrupt Flag */
> -#define ISR_FUIF	BIT(1)		/* Fifo Underrun Interrupt Flag */
> +#define ISR_FUWIF	BIT(1)		/* Fifo Underrun Warning Interrupt Flag */
>   #define ISR_TERRIF	BIT(2)		/* Transfer ERRor Interrupt Flag */
>   #define ISR_RRIF	BIT(3)		/* Register Reload Interrupt Flag */
> +#define ISR_FUEIF	BIT(6)		/* Fifo Underrun Error Interrupt Flag */
> +#define ISR_CRCIF	BIT(7)		/* CRC Error Interrupt Flag */
>   
>   #define EDCR_OCYEN	BIT(25)		/* Output Conversion to YCbCr 422: ENable */
>   #define EDCR_OCYSEL	BIT(26)		/* Output Conversion to YCbCr 422: SELection of the CCIR */
> @@ -231,6 +235,8 @@
>   
>   #define NB_PF		8		/* Max nb of HW pixel format */
>   
> +#define FUT_DFT		128		/* Default value of fifo underrun threshold */
> +
>   /*
>    * Skip the first value and the second in case CRC was enabled during
>    * the thread irq. This is to be sure CRC value is relevant for the
> @@ -711,12 +717,13 @@ static irqreturn_t ltdc_irq_thread(int irq, void *arg)
>   			ltdc_irq_crc_handle(ldev, crtc);
>   	}
>   
> -	/* Save FIFO Underrun & Transfer Error status */
>   	mutex_lock(&ldev->err_lock);
> -	if (ldev->irq_status & ISR_FUIF)
> -		ldev->error_status |= ISR_FUIF;
>   	if (ldev->irq_status & ISR_TERRIF)
> -		ldev->error_status |= ISR_TERRIF;
> +		ldev->transfer_err++;
> +	if (ldev->irq_status & ISR_FUEIF)
> +		ldev->fifo_err++;
> +	if (ldev->irq_status & ISR_FUWIF)
> +		ldev->fifo_warn++;
>   	mutex_unlock(&ldev->err_lock);
>   
>   	return IRQ_HANDLED;
> @@ -775,7 +782,7 @@ static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
>   	regmap_write(ldev->regmap, LTDC_BCCR, BCCR_BCBLACK);
>   
>   	/* Enable IRQ */
> -	regmap_set_bits(ldev->regmap, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
> +	regmap_set_bits(ldev->regmap, LTDC_IER, IER_FUWIE | IER_FUEIE | IER_RRIE | IER_TERRIE);
>   
>   	/* Commit shadow registers = update planes at next vblank */
>   	if (!ldev->caps.plane_reg_shadow)
> @@ -801,13 +808,20 @@ static void ltdc_crtc_atomic_disable(struct drm_crtc *crtc,
>   				  LXCR_CLUTEN | LXCR_LEN, 0);
>   
>   	/* disable IRQ */
> -	regmap_clear_bits(ldev->regmap, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
> +	regmap_clear_bits(ldev->regmap, LTDC_IER, IER_FUWIE | IER_FUEIE | IER_RRIE | IER_TERRIE);
>   
>   	/* immediately commit disable of layers before switching off LTDC */
>   	if (!ldev->caps.plane_reg_shadow)
>   		regmap_set_bits(ldev->regmap, LTDC_SRCR, SRCR_IMR);
>   
>   	pm_runtime_put_sync(ddev->dev);
> +
> +	/*  clear interrupt error counters */
> +	mutex_lock(&ldev->err_lock);
> +	ldev->transfer_err = 0;
> +	ldev->fifo_err = 0;
> +	ldev->fifo_warn = 0;
> +	mutex_unlock(&ldev->err_lock);
>   }
>   
>   #define CLK_TOLERANCE_HZ 50
> @@ -1168,6 +1182,18 @@ static int ltdc_crtc_verify_crc_source(struct drm_crtc *crtc,
>   	return 0;
>   }
>   
> +static void ltdc_crtc_atomic_print_state(struct drm_printer *p,
> +					 const struct drm_crtc_state *state)
> +{
> +	struct drm_crtc *crtc = state->crtc;
> +	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> +
> +	drm_printf(p, "\ttransfer_error=%d\n", ldev->transfer_err);
> +	drm_printf(p, "\tfifo_underrun_error=%d\n", ldev->fifo_err);
> +	drm_printf(p, "\tfifo_underrun_warning=%d\n", ldev->fifo_warn);
> +	drm_printf(p, "\tfifo_underrun_threshold=%d\n", ldev->fifo_threshold);
> +}
> +
>   static const struct drm_crtc_funcs ltdc_crtc_funcs = {
>   	.destroy = drm_crtc_cleanup,
>   	.set_config = drm_atomic_helper_set_config,
> @@ -1178,6 +1204,7 @@ static const struct drm_crtc_funcs ltdc_crtc_funcs = {
>   	.enable_vblank = ltdc_crtc_enable_vblank,
>   	.disable_vblank = ltdc_crtc_disable_vblank,
>   	.get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
> +	.atomic_print_state = ltdc_crtc_atomic_print_state,
>   };
>   
>   static const struct drm_crtc_funcs ltdc_crtc_with_crc_support_funcs = {
> @@ -1192,6 +1219,7 @@ static const struct drm_crtc_funcs ltdc_crtc_with_crc_support_funcs = {
>   	.get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp,
>   	.set_crc_source = ltdc_crtc_set_crc_source,
>   	.verify_crc_source = ltdc_crtc_verify_crc_source,
> +	.atomic_print_state = ltdc_crtc_atomic_print_state,
>   };
>   
>   /*
> @@ -1452,13 +1480,21 @@ static void ltdc_plane_atomic_update(struct drm_plane *plane,
>   	ldev->plane_fpsi[plane->index].counter++;
>   
>   	mutex_lock(&ldev->err_lock);
> -	if (ldev->error_status & ISR_FUIF) {
> -		DRM_WARN("ltdc fifo underrun: please verify display mode\n");
> -		ldev->error_status &= ~ISR_FUIF;
> +	if (ldev->transfer_err) {
> +		DRM_WARN("ltdc transfer error: %d\n", ldev->transfer_err);
> +		ldev->transfer_err = 0;
>   	}
> -	if (ldev->error_status & ISR_TERRIF) {
> -		DRM_WARN("ltdc transfer error\n");
> -		ldev->error_status &= ~ISR_TERRIF;
> +
> +	if (ldev->caps.fifo_threshold) {
> +		if (ldev->fifo_err) {
> +			DRM_WARN("ltdc fifo underrun: please verify display mode\n");
> +			ldev->fifo_err = 0;
> +		}
> +	} else {
> +		if (ldev->fifo_warn >= ldev->fifo_threshold) {
> +			DRM_WARN("ltdc fifo underrun: please verify display mode\n");
> +			ldev->fifo_warn = 0;
> +		}
>   	}
>   	mutex_unlock(&ldev->err_lock);
>   }
> @@ -1700,6 +1736,10 @@ static void ltdc_encoder_enable(struct drm_encoder *encoder)
>   
>   	DRM_DEBUG_DRIVER("\n");
>   
> +	/* set fifo underrun threshold register */
> +	if (ldev->caps.fifo_threshold)
> +		regmap_write(ldev->regmap, LTDC_FUT, ldev->fifo_threshold);
> +
>   	/* Enable LTDC */
>   	regmap_set_bits(ldev->regmap, LTDC_GCR, GCR_LTDCEN);
>   }
> @@ -1801,6 +1841,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
>   		ldev->caps.crc = false;
>   		ldev->caps.dynamic_zorder = false;
>   		ldev->caps.plane_rotation = false;
> +		ldev->caps.fifo_threshold = false;
>   		break;
>   	case HWVER_20101:
>   		ldev->caps.layer_ofs = LAY_OFS_0;
> @@ -1818,6 +1859,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
>   		ldev->caps.crc = false;
>   		ldev->caps.dynamic_zorder = false;
>   		ldev->caps.plane_rotation = false;
> +		ldev->caps.fifo_threshold = false;
>   		break;
>   	case HWVER_40100:
>   		ldev->caps.layer_ofs = LAY_OFS_1;
> @@ -1835,6 +1877,7 @@ static int ltdc_get_caps(struct drm_device *ddev)
>   		ldev->caps.crc = true;
>   		ldev->caps.dynamic_zorder = true;
>   		ldev->caps.plane_rotation = true;
> +		ldev->caps.fifo_threshold = true;
>   		break;
>   	default:
>   		return -ENODEV;
> @@ -1959,9 +2002,6 @@ int ltdc_load(struct drm_device *ddev)
>   		goto err;
>   	}
>   
> -	/* Disable interrupts */
> -	regmap_clear_bits(ldev->regmap, LTDC_IER, IER_LIE | IER_RRIE | IER_FUIE | IER_TERRIE);
> -
>   	ret = ltdc_get_caps(ddev);
>   	if (ret) {
>   		DRM_ERROR("hardware identifier (0x%08x) not supported!\n",
> @@ -1969,8 +2009,22 @@ int ltdc_load(struct drm_device *ddev)
>   		goto err;
>   	}
>   
> +	/* Disable interrupts */
> +	if (ldev->caps.fifo_threshold)
> +		regmap_clear_bits(ldev->regmap, LTDC_IER, IER_LIE | IER_RRIE | IER_FUWIE |
> +				  IER_TERRIE);
> +	else
> +		regmap_clear_bits(ldev->regmap, LTDC_IER, IER_LIE | IER_RRIE | IER_FUWIE |
> +				  IER_TERRIE | IER_FUEIE);
> +
>   	DRM_DEBUG_DRIVER("ltdc hw version 0x%08x\n", ldev->caps.hw_version);
>   
> +	/* initialize default value for fifo underrun threshold & clear interrupt error counters */
> +	ldev->transfer_err = 0;
> +	ldev->fifo_err = 0;
> +	ldev->fifo_warn = 0;
> +	ldev->fifo_threshold = FUT_DFT;
> +
>   	for (i = 0; i < ldev->caps.nb_irq; i++) {
>   		irq = platform_get_irq(pdev, i);
>   		if (irq < 0) {
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index 15139980d8ea..9d488043ffdb 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -30,6 +30,7 @@ struct ltdc_caps {
>   	bool crc;		/* cyclic redundancy check supported */
>   	bool dynamic_zorder;	/* dynamic z-order */
>   	bool plane_rotation;	/* plane rotation */
> +	bool fifo_threshold;	/* fifo underrun threshold supported */
>   };
>   
>   #define LTDC_MAX_LAYER	4
> @@ -45,8 +46,11 @@ struct ltdc_device {
>   	struct clk *pixel_clk;	/* lcd pixel clock */
>   	struct mutex err_lock;	/* protecting error_status */
>   	struct ltdc_caps caps;
> -	u32 error_status;
>   	u32 irq_status;
> +	u32 fifo_err;		/* fifo underrun error counter */
> +	u32 fifo_warn;		/* fifo underrun warning counter */
> +	u32 fifo_threshold;	/* fifo underrun threshold */
> +	u32 transfer_err;	/* transfer error counter */
>   	struct fps_info plane_fpsi[LTDC_MAX_LAYER];
>   	struct drm_atomic_state *suspend_state;
>   	int crc_skip_count;
Dear Yannick,
Many thanks for your patch,
Applied on drm-misc-next.
Have a good day
Philippe :-)