FAILED: patch "[PATCH] drm: atmel-hlcdc: enable clock before configuring timing" failed to apply to 4.9-stable tree

FAILED: patch "[PATCH] drm: atmel-hlcdc: enable clock before configuring timing" failed to apply to 4.9-stable tree

[gregkh]

The patch below does not apply to the 4.9-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-email-claudiu.beznea@microchip.com

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