linux-kernel - [PATCH 4/4] drm/fsl-dcu: do not update when modifying irq registers

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Message-Id: <20160906040233.32471-5-stefan@agner.ch>
Date:   Mon,  5 Sep 2016 21:02:33 -0700
From:   Stefan Agner <stefan@...er.ch>
To:     dri-devel@...ts.freedesktop.org, meng.yi@....com
Cc:     alison.wang@...escale.com, jianwei.wang.chn@...il.com,
        linux-kernel@...r.kernel.org, Stefan Agner <stefan@...er.ch>
Subject: [PATCH 4/4] drm/fsl-dcu: do not update when modifying irq registers

The IRQ status and mask registers are not "double buffered" according
to the reference manual. Hence, there is no extra transfer/update
write needed when modifying these registers.

Signed-off-by: Stefan Agner <stefan@...er.ch>
---
 drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c | 4 ----
 1 file changed, 4 deletions(-)

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 092aaec..4e700bc4 100644
--- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
+++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_drv.c
@@ -59,8 +59,6 @@ static int fsl_dcu_drm_irq_init(struct drm_device *dev)
 
 	regmap_write(fsl_dev->regmap, DCU_INT_STATUS, 0);
 	regmap_write(fsl_dev->regmap, DCU_INT_MASK, ~0);
-	regmap_write(fsl_dev->regmap, DCU_UPDATE_MODE,
-		     DCU_UPDATE_MODE_READREG);
 
 	return ret;
 }
@@ -139,8 +137,6 @@ static irqreturn_t fsl_dcu_drm_irq(int irq, void *arg)
 		drm_handle_vblank(dev, 0);
 
 	regmap_write(fsl_dev->regmap, DCU_INT_STATUS, int_status);
-	regmap_write(fsl_dev->regmap, DCU_UPDATE_MODE,
-		     DCU_UPDATE_MODE_READREG);
 
 	return IRQ_HANDLED;
 }
-- 
2.9.3