[PATCH v2] gpu: ipu-v3: pre: only use internal clock gating

[Lucas Stach]

By setting the SFTRST bit, the PRE will be held in the lowest power state
with clocks to the internal blocks gated. When external clock gating is
used (from the external clock controller, or by setting the CLKGATE bit)
the PRE will sporadically fail to start.

Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
---
v2: add missing clk_disable_unprepare in remove path

This is a fix for newly introduced functionality and should be applied
for 4.12 fixes.
---
 drivers/gpu/ipu-v3/ipu-pre.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/ipu-v3/ipu-pre.c b/drivers/gpu/ipu-v3/ipu-pre.c
index c55563379e2e..c35f74c83065 100644
--- a/drivers/gpu/ipu-v3/ipu-pre.c
+++ b/drivers/gpu/ipu-v3/ipu-pre.c
@@ -131,8 +131,6 @@ int ipu_pre_get(struct ipu_pre *pre)
 	if (pre->in_use)
 		return -EBUSY;
 
-	clk_prepare_enable(pre->clk_axi);
-
 	/* first get the engine out of reset and remove clock gating */
 	writel(0, pre->regs + IPU_PRE_CTRL);
 
@@ -149,12 +147,7 @@ int ipu_pre_get(struct ipu_pre *pre)
 
 void ipu_pre_put(struct ipu_pre *pre)
 {
-	u32 val;
-
-	val = IPU_PRE_CTRL_SFTRST | IPU_PRE_CTRL_CLKGATE;
-	writel(val, pre->regs + IPU_PRE_CTRL);
-
-	clk_disable_unprepare(pre->clk_axi);
+	writel(IPU_PRE_CTRL_SFTRST, pre->regs + IPU_PRE_CTRL);
 
 	pre->in_use = false;
 }
@@ -249,6 +242,8 @@ static int ipu_pre_probe(struct platform_device *pdev)
 	if (!pre->buffer_virt)
 		return -ENOMEM;
 
+	clk_prepare_enable(pre->clk_axi);
+
 	pre->dev = dev;
 	platform_set_drvdata(pdev, pre);
 	mutex_lock(&ipu_pre_list_mutex);
@@ -268,6 +263,8 @@ static int ipu_pre_remove(struct platform_device *pdev)
 	available_pres--;
 	mutex_unlock(&ipu_pre_list_mutex);
 
+	clk_disable_unprepare(pre->clk_axi);
+
 	if (pre->buffer_virt)
 		gen_pool_free(pre->iram, (unsigned long)pre->buffer_virt,
 			      IPU_PRE_MAX_WIDTH * IPU_PRE_NUM_SCANLINES * 4);
-- 
2.11.0