[PATCH 07/14] gpu: host1x: mipi: Preserve the contents of MIPI_CAL_CTRL

[Thierry Reding]

From: Sean Paul <seanpaul at chromium.org>

By paving the CTRL reg value, the current code changes MIPI_CAL_PRESCALE
("Auto-cal calibration step prescale") from 1us to 0.1us (val=0). In the
description for PHY's noise filter (MIPI_CAL_NOISE_FLT), the TRM states
that if the value of the prescale is 0 (or 0.1us), the filter should be
set between 2-5. However, the current code sets it to 0.

For now, let's keep the prescale and filter values as-is, which is most
likely the power-on-reset values of 0x2 and 0xa, respectively.

Signed-off-by: Sean Paul <seanpaul at chromium.org>
Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/host1x/mipi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/host1x/mipi.c b/drivers/gpu/host1x/mipi.c
index a3e215a0116f..0d8c3ae8db6a 100644
--- a/drivers/gpu/host1x/mipi.c
+++ b/drivers/gpu/host1x/mipi.c
@@ -208,7 +208,9 @@ int tegra_mipi_calibrate(struct tegra_mipi_device *device)
 		tegra_mipi_writel(device->mipi, value, modules[i].reg);
 	}
 
-	tegra_mipi_writel(device->mipi, MIPI_CAL_CTRL_START, MIPI_CAL_CTRL);
+	value = tegra_mipi_readl(device->mipi, MIPI_CAL_CTRL);
+	value |= MIPI_CAL_CTRL_START;
+	tegra_mipi_writel(device->mipi, value, MIPI_CAL_CTRL);
 
 	err = tegra_mipi_wait(device->mipi);
 
-- 
2.1.2