Re: [RFC PATCH] media: rcar-csi2: Fix field detection

From: Steve Longerbeam
Date: Wed Apr 17 2019 - 13:57:06 EST

Hi Nklas,

On 4/16/19 4:59 PM, Steve Longerbeam wrote:
Hi Niklas,

On 4/16/19 4:50 PM, Niklas SÃderlund wrote:
Hi Steve,

Thanks for your work.

I upported most rcar-csi2 patches but a few of them are still pending,
an alternating version based on this BSP patch is already on its way.

https://patchwork.linuxtv.org/patch/55623/

Great, that patch confirms that FLD_NUM should be set to 0 or 1 when setting FLD_DET_SEL = 0x01.

But your patch has it inverted. NTSC should be FLD_NUM=1, PAL should be FLD_NUM=0. Can you please confirm that after reading the commit description of my RFC patch.

Can you please confirm that your patch at https://patchwork.linuxtv.org/patch/55623 has the FLD_NUM bits inverted? It's the most important question regarding this. Please review my reasoning in the RFC patch. NTSC should be FLD_NUM=1, PAL should be FLD_NUM=0.

Also, slightly off-topic, but another question:

Do you know if it is possible to capture from a source that is sending SEQ-BT/TB and transfer to userspace as unmodified SEQ-BT/TB without requiring the capture of each field individually and concatenating them?

In other words, treat the frame from the source the same as progressive, i.e. as if the source were sending V4L2_FIELD_NONE. That is, program VnMC.IM bits as VNMC_IM_ODD_EVEN and use continuous frame capture mode.

TIA,
Steve






On 2019-04-16 16:38:07 -0700, Steve Longerbeam wrote:
The RCAR Gen3 hardware manual doesn't mention that the "Word Count" field
in the MIPI CSI-2 Frame Start packet is really the frame number. FS packets
are short packets, and short packets do not have a WC but rather a 16-bit
data field, and for Frame synchronization packets (FS/FE) the 16-bit data
field contains a frame number.

Here is a reprinting from the MIPI CSI-2 specification, version 2
(section 9.1.2 Low Level Protocol Short Packet Format):

"Figure 42 and Figure 43 show the Low Level Protocol Short Packet
structures for the D-PHY and C-PHY physical layer options, respectively.
For each option, the Short Packet structure matches the Packet Header of
the corresponding Low Level Protocol Long Packet structure with the
exception that the Packet Header Word Count (WC) field shall be replaced
by the Short Packet Data Field...For Frame Synchronization Data Types
the Short Packet Data Field shall be the frame number..."

Also in section 9.8.1 Frame Synchronization Packets, the CSI-2 spec reads:

"The behavior of the 16-bit frame number shall be as one of the following
- Frame number is always zero â frame number is inoperative.
- Frame number increments by 1 for every FS packet with the same Virtual
ÂÂ Channel and is periodically reset to one e.g. 1, 2, 1, 2, 1, 2, 1, 2 or
ÂÂ 1, 2, 3, 4, 1, 2, 3, 4"

So from the above, FLD_NUM in the FLD register matches against the
frame number transmitted by the CSI-2 source in the Frame Start Packet,
and goes as "1,2,1,2,1,2" or "1,2,3,4,...,1,2,3,4". If there is a match,
the RCAR CSI-2 receiver declares the field as the even, e.g. the BOTTOM,
field.

NTSC transmits bottom/even field first, and PAL and HD transmit top/odd
field first. So fields with a frame number 1 in the CSI-2 Frame Start
Packet are bottom/even fields for NTSC, and frame number 2 are bottom/even
fields for PAL/HD.

But the above assumes the transmitting CSI-2 sensor is sending frame
numbers in the sequence "1,2,1,2,...". But according to the CSI-2 spec,
sensors are also allowed to send frame numbers that simply increment as
in "1,2,3,4,...". To generalize to catch those cases, set FLD_DET_SEL
to 0x01, which according to the RCAR Gen3 hardware manual means "the
field is detected as the EVEN field when FLD_NUM[0] matches WC[0]".
Then, the even/bottom fields have odd frame numbers for NTSC, and even
frame numbers for PAL (this patch assumes HDMI sources will not
implement .g_std(), so std will be 0 in that case).

Finally, set the FLD register to non-zero value only if trnsmitter is
sending ALTERNATE fields.

Signed-off-by: Steve Longerbeam <slongerbeam@xxxxxxxxx>
---
 drivers/media/platform/rcar-vin/rcar-csi2.c | 37 ++++++++++++++++++---
 1 file changed, 32 insertions(+), 5 deletions(-)

diff --git a/drivers/media/platform/rcar-vin/rcar-csi2.c b/drivers/media/platform/rcar-vin/rcar-csi2.c
index a438ec2c218f..c5bee20d7907 100644
--- a/drivers/media/platform/rcar-vin/rcar-csi2.c
+++ b/drivers/media/platform/rcar-vin/rcar-csi2.c
@@ -67,6 +67,7 @@ struct rcar_csi2;
 /* Field Detection Control */
 #define FLD_REG 0x1c
 #define FLD_FLD_NUM(n) (((n) & 0xff) << 16)
+#define FLD_FLD_DET_SEL(n)ÂÂÂÂÂÂÂ (((n) & 0x3) << 4)
 #define FLD_FLD_EN4 BIT(3)
 #define FLD_FLD_EN3 BIT(2)
 #define FLD_FLD_EN2 BIT(1)
@@ -462,10 +463,11 @@ static int rcsi2_calc_mbps(struct rcar_csi2 *priv, unsigned int bpp)
ÂÂÂÂÂ return mbps;
 }
 -static int rcsi2_start(struct rcar_csi2 *priv)
+static int rcsi2_start(struct rcar_csi2 *priv, struct v4l2_subdev *nextsd)
 {
ÂÂÂÂÂ const struct rcar_csi2_format *format;
-ÂÂÂ u32 phycnt, vcdt = 0, vcdt2 = 0;
+ÂÂÂ u32 phycnt, vcdt = 0, vcdt2 = 0, fld = 0;
+ÂÂÂ v4l2_std_id std = 0;
ÂÂÂÂÂ unsigned int i;
ÂÂÂÂÂ int mbps, ret;
 @@ -476,6 +478,10 @@ static int rcsi2_start(struct rcar_csi2 *priv)
ÂÂÂÂÂ /* Code is validated in set_fmt. */
ÂÂÂÂÂ format = rcsi2_code_to_fmt(priv->mf.code);
 + ret = v4l2_subdev_call(nextsd, video, g_std, &std);
+ÂÂÂ if (ret < 0 && ret != -ENOIOCTLCMD && ret != -ENODEV)
+ÂÂÂÂÂÂÂ return ret;
+
ÂÂÂÂÂ /*
ÂÂÂÂÂÂ * Enable all supported CSI-2 channels with virtual channel and
ÂÂÂÂÂÂ * data type matching.
@@ -509,9 +515,30 @@ static int rcsi2_start(struct rcar_csi2 *priv)
ÂÂÂÂÂ rcsi2_reset(priv);
ÂÂÂÂÂ rcsi2_write(priv, PHTC_REG, 0);
 + /*
+ÂÂÂÂ * NTSC standard transmits even/bottom field first, then odd/top.
+ÂÂÂÂ * PAL standard and interlaced HD transmit odd/top field first,
+ÂÂÂÂ * then even/bottom.
+ÂÂÂÂ *
+ÂÂÂÂ * For CSI-2 sensors that transmit frame numbers (in the CSI-2
+ÂÂÂÂ * Frame Start packet) as "1,2,1,2,..." or "1,2,3,4,5,...", then:
+ÂÂÂÂ *
+ÂÂÂÂ * - for NTSC, the even/bottom fields have odd frame numbers.
+ÂÂÂÂ * - for PAL and HD, the even/bottom fields have even frame numbers.
+ÂÂÂÂ */
+ÂÂÂ if (priv->mf.field == V4L2_FIELD_ALTERNATE) {
+ÂÂÂÂÂÂÂ fld = FLD_FLD_DET_SEL(1) | FLD_FLD_EN4 | FLD_FLD_EN3 |
+ÂÂÂÂÂÂÂÂÂÂÂ FLD_FLD_EN2 | FLD_FLD_EN;
+
+ÂÂÂÂÂÂÂ if (std & V4L2_STD_525_60)
+ÂÂÂÂÂÂÂÂÂÂÂ fld |= FLD_FLD_NUM(1); /* NTSC */
+ÂÂÂÂÂÂÂ else
+ÂÂÂÂÂÂÂÂÂÂÂ fld |= FLD_FLD_NUM(0); /* PAL or HD */
+ÂÂÂ }
+
ÂÂÂÂÂ /* Configure */
-ÂÂÂ rcsi2_write(priv, FLD_REG, FLD_FLD_NUM(2) | FLD_FLD_EN4 |
-ÂÂÂÂÂÂÂÂÂÂÂ FLD_FLD_EN3 | FLD_FLD_EN2 | FLD_FLD_EN);
+ÂÂÂ rcsi2_write(priv, FLD_REG, fld);
+
ÂÂÂÂÂ rcsi2_write(priv, VCDT_REG, vcdt);
ÂÂÂÂÂ if (vcdt2)
ÂÂÂÂÂÂÂÂÂ rcsi2_write(priv, VCDT2_REG, vcdt2);
@@ -591,7 +618,7 @@ static int rcsi2_s_stream(struct v4l2_subdev *sd, int enable)
ÂÂÂÂÂ if (enable && priv->stream_count == 0) {
ÂÂÂÂÂÂÂÂÂ pm_runtime_get_sync(priv->dev);
 - ret = rcsi2_start(priv);
+ÂÂÂÂÂÂÂ ret = rcsi2_start(priv, nextsd);
ÂÂÂÂÂÂÂÂÂ if (ret) {
ÂÂÂÂÂÂÂÂÂÂÂÂÂ pm_runtime_put(priv->dev);
ÂÂÂÂÂÂÂÂÂÂÂÂÂ goto out;
--
2.17.1