linux-kernel - [PATCH 1/7] drm/fsl-dcu: specify volatile registers

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Message-Id: <1447900970-15936-2-git-send-email-stefan@agner.ch>
Date:	Wed, 18 Nov 2015 18:42:44 -0800
From:	Stefan Agner <stefan@...er.ch>
To:	airlied@...ux.ie, daniel.vetter@...ll.ch,
	jianwei.wang.chn@...il.com
Cc:	alison.wang@...escale.com, mark.yao@...k-chips.com,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	Stefan Agner <stefan@...er.ch>
Subject: [PATCH 1/7] drm/fsl-dcu: specify volatile registers

Since we are using cached registers, we need to specify volatile
registers explicitly to avoid reading their value from the cache.
This allows to read the correct interrupt status in fsl_dcu_drm_irq
and clear the asserted bits only.

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
index 1930234..d6e27af 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
@@ -28,11 +28,21 @@
 #include "fsl_dcu_drm_crtc.h"
 #include "fsl_dcu_drm_drv.h"
 
+static bool fsl_dcu_drm_is_volatile_reg(struct device *dev, unsigned int reg)
+{
+	if (reg == DCU_INT_STATUS || reg == DCU_UPDATE_MODE)
+		return true;
+
+	return false;
+}
+
 static const struct regmap_config fsl_dcu_regmap_config = {
 	.reg_bits = 32,
 	.reg_stride = 4,
 	.val_bits = 32,
 	.cache_type = REGCACHE_RBTREE,
+
+	.volatile_reg = fsl_dcu_drm_is_volatile_reg,
 };
 
 static int fsl_dcu_drm_irq_init(struct drm_device *dev)
@@ -129,7 +139,7 @@ static irqreturn_t fsl_dcu_drm_irq(int irq, void *arg)
 	if (int_status & DCU_INT_STATUS_VBLANK)
 		drm_handle_vblank(dev, 0);
 
-	ret = regmap_write(fsl_dev->regmap, DCU_INT_STATUS, 0xffffffff);
+	ret = regmap_write(fsl_dev->regmap, DCU_INT_STATUS, int_status);
 	if (ret)
 		dev_err(dev->dev, "set DCU_INT_STATUS failed\n");
 	ret = regmap_write(fsl_dev->regmap, DCU_UPDATE_MODE,
-- 
2.6.2

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