The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2c1fb9d86f6820abbfaa38a6836157c76ccb4e7b Mon Sep 17 00:00:00 2001

From: Claudiu Beznea claudiu.beznea@microchip.com Date: Wed, 18 Dec 2019 14:28:25 +0200 Subject: [PATCH] drm: atmel-hlcdc: enable clock before configuring timing engine

Changing pixel clock source without having this clock source enabled will block the timing engine and the next operations after (in this case setting ATMEL_HLCDC_CFG(5) settings in atmel_hlcdc_crtc_mode_set_nofb() will fail). It is recomended (although in datasheet this is not present) to actually enabled pixel clock source before doing any changes on timing enginge (only SAM9X60 datasheet specifies that the peripheral clock and pixel clock must be enabled before using LCD controller).

Fixes: 1a396789f65a ("drm: add Atmel HLCDC Display Controller support") Signed-off-by: Claudiu Beznea claudiu.beznea@microchip.com Signed-off-by: Sam Ravnborg sam@ravnborg.org Cc: Boris Brezillon boris.brezillon@free-electrons.com Cc: stable@vger.kernel.org # v4.0+ Link: https://patchwork.freedesktop.org/patch/msgid/1576672109-22707-3-git-send-em...

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c index 5040ed8d0871..721fa88bf71d 100644 --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c @@ -73,7 +73,11 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c) unsigned long prate; unsigned int mask = ATMEL_HLCDC_CLKDIV_MASK | ATMEL_HLCDC_CLKPOL; unsigned int cfg = 0; - int div; + int div, ret; + + ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk); + if (ret) + return;

vm.vfront_porch = adj->crtc_vsync_start - adj->crtc_vdisplay; vm.vback_porch = adj->crtc_vtotal - adj->crtc_vsync_end; @@ -147,6 +151,8 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc *c) ATMEL_HLCDC_VSPSU | ATMEL_HLCDC_VSPHO | ATMEL_HLCDC_GUARDTIME_MASK | ATMEL_HLCDC_MODE_MASK, cfg); + + clk_disable_unprepare(crtc->dc->hlcdc->sys_clk); }

static enum drm_mode_status