Running (and terminating) Weston on i.MX8MP sometimes produced black or grey screens. The LCDIF3 INT_STATUS_D0 register showed a FIFO underrun:
32FC6024: 1000002 The PANIC0_THRES register was set to: 32FC6238: AA0154 which apparently meant low = 2736 bytes (0xAA * 16 + 16), high = 5456 bytes (0x154 * 16 + 16). With this patch (based on NXP's driver) the watermarks are only 16 bytes higher (register values increased by 1) and the underruns are gone. Tested on Solidrun Hummingboard Mate with a 1080p60 HDMI display. Signed-off-by: Krzysztof Hałasa <[email protected]> --- a/drivers/gpu/drm/mxsfb/lcdif_kms.c +++ b/drivers/gpu/drm/mxsfb/lcdif_kms.c @@ -353,8 +353,8 @@ static void lcdif_enable_controller(struct lcdif_drm_private *lcdif) u32 reg; /* Set FIFO Panic watermarks, low 1/3, high 2/3 . */ - writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, 1 * PANIC0_THRES_MAX / 3) | - FIELD_PREP(PANIC0_THRES_HIGH_MASK, 2 * PANIC0_THRES_MAX / 3), + writel(FIELD_PREP(PANIC0_THRES_LOW_MASK, DIV_ROUND_UP(1 * PANIC0_THRES_MAX, 3)) | + FIELD_PREP(PANIC0_THRES_HIGH_MASK, DIV_ROUND_UP(2 * PANIC0_THRES_MAX, 3)), lcdif->base + LCDC_V8_PANIC0_THRES); /* -- Krzysztof "Chris" Hałasa Sieć Badawcza Łukasiewicz Przemysłowy Instytut Automatyki i Pomiarów PIAP Al. Jerozolimskie 202, 02-486 Warszawa
