[media] stk1160: Add frame scaling support

This commit implements frame decimation for stk1160, which allows
to support format changes instead of a static frame size.

The stk1160 supports independent row and column decimation, in two
different modes:
 * set a number of rows/columns units to skip for each unit sent.
 * set a number of rows/columns units to send for each unit skipped.

This effectively allows to achieve different frame scaling ratios.

The unit number can be set to either two row/columns sent/skipped,
or four row/columns sent/skipped. Since the video format (UYVY)
has 4-bytes, using a unit number of two row/columns results
in frame color 'shifting', so set to four row/columns sent/skipped.

Signed-off-by: Michael Stegemann <michael@stegemann.it>
Signed-off-by: Dale Hamel <dale.hamel@srvthe.net>
Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/drivers/media/usb/stk1160/stk1160-reg.h b/drivers/media/usb/stk1160/stk1160-reg.h
index 3e49da6e7edd..81ff3a15d96e 100644
--- a/drivers/media/usb/stk1160/stk1160-reg.h
+++ b/drivers/media/usb/stk1160/stk1160-reg.h
@@ -33,6 +33,40 @@
  */
 #define STK1160_DCTRL			0x100
 
+/*
+ * Decimation Control Register:
+ * Byte 104: Horizontal Decimation Line Unit Count
+ * Byte 105: Vertical Decimation Line Unit Count
+ * Byte 106: Decimation Control
+ * Bit 0 - Horizontal Decimation Control
+ *   0 Horizontal decimation is disabled.
+ *   1 Horizontal decimation is enabled.
+ * Bit 1 - Decimates Half or More Column
+ *   0 Decimates less than half from original column,
+ *     send count unit (0x105) before each unit skipped.
+ *   1 Decimates half or more from original column,
+ *     skip count unit (0x105) before each unit sent.
+ * Bit 2 - Vertical Decimation Control
+ *   0 Vertical decimation is disabled.
+ *   1 Vertical decimation is enabled.
+ * Bit 3 - Vertical Greater or Equal to Half
+ *   0 Decimates less than half from original row,
+ *     send count unit (0x105) before each unit skipped.
+ *   1 Decimates half or more from original row,
+ *     skip count unit (0x105) before each unit sent.
+ * Bit 4 - Decimation Unit
+ *  0 Decimation will work with 2 rows or columns per unit.
+ *  1 Decimation will work with 4 rows or columns per unit.
+ */
+#define STK1160_DMCTRL_H_UNITS		0x104
+#define STK1160_DMCTRL_V_UNITS		0x105
+#define STK1160_DMCTRL			0x106
+#define  STK1160_H_DEC_EN		BIT(0)
+#define  STK1160_H_DEC_MODE		BIT(1)
+#define  STK1160_V_DEC_EN		BIT(2)
+#define  STK1160_V_DEC_MODE		BIT(3)
+#define  STK1160_DEC_UNIT_SIZE		BIT(4)
+
 /* Capture Frame Start Position */
 #define STK116_CFSPO			0x110
 #define STK116_CFSPO_STX_L		0x110