[RFC PATCH v2 16/18] media: tegra-video: Compute settle times based on the clock rate

From: Sowjanya Komatineni
Date: Tue Jun 16 2020 - 21:39:59 EST

Settle time determines the number of cil clock cyles to wait after
LP00 when moving from LP to HS.

This patch computes T-CLK-SETTLE and T-HS-SETTLE times based on cil
clock rate and pixel rate from the sensor and programs them during
streaming.

T-CLK-SETTLE time is the interval during which receiver will ignore
any HS transitions on clock lane starting from the beginning of
T-CLK-PREPARE.

T-HS-SETTLE time is the interval during which recevier will ignore
any HS transitions on data lane starting from the beginning of
T-HS-PREPARE.

Signed-off-by: Sowjanya Komatineni <skomatineni@xxxxxxxxxx>
---
drivers/staging/media/tegra-video/csi.c | 55 ++++++++++++++++++++++++++++
drivers/staging/media/tegra-video/csi.h | 5 +++
drivers/staging/media/tegra-video/tegra210.c | 17 ++++++++-
3 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
index f598b76..a8c0186 100644
--- a/drivers/staging/media/tegra-video/csi.c
+++ b/drivers/staging/media/tegra-video/csi.c
@@ -19,6 +19,8 @@
#include "csi.h"
#include "video.h"

+#define MHZ 1000000
+
static inline struct tegra_csi *
host1x_client_to_csi(struct host1x_client *client)
{
@@ -235,6 +237,59 @@ static int tegra_csi_g_frame_interval(struct v4l2_subdev *subdev,
return 0;
}

+static unsigned int csi_get_pixel_rate(struct tegra_csi_channel *csi_chan)
+{
+ struct tegra_vi_channel *chan;
+ struct v4l2_subdev *src_subdev;
+ struct v4l2_ctrl *ctrl;
+
+ chan = v4l2_get_subdev_hostdata(&csi_chan->subdev);
+ src_subdev = tegra_channel_get_remote_subdev(chan, true);
+ ctrl = v4l2_ctrl_find(src_subdev->ctrl_handler, V4L2_CID_PIXEL_RATE);
+ if (ctrl)
+ return v4l2_ctrl_g_ctrl_int64(ctrl);
+
+ return 0;
+}
+
+void tegra_csi_calc_settle_time(struct tegra_csi_channel *csi_chan,
+ u8 *clk_settle_time,
+ u8 *ths_settle_time)
+{
+ struct tegra_csi *csi = csi_chan->csi;
+ unsigned int cil_clk_mhz;
+ unsigned int pix_clk_mhz;
+ int clk_idx = (csi_chan->csi_port_num >> 1) + 1;
+
+ cil_clk_mhz = clk_get_rate(csi->clks[clk_idx].clk) / MHZ;
+ pix_clk_mhz = csi_get_pixel_rate(csi_chan) / MHZ;
+
+ /*
+ * CLK Settle time is the interval during which HS receiver should
+ * ignore any clock lane HS transitions, starting from the beginning
+ * of T-CLK-PREPARE.
+ * Per DPHY specification, T-CLK-SETTLE should be between 95ns ~ 300ns
+ *
+ * 95ns < (clk-settle-programmed + 7) * lp clk period < 300ns
+ * midpoint = 197.5 ns
+ */
+ *clk_settle_time = ((95 + 300) * cil_clk_mhz - 14000) / 2000;
+
+ /*
+ * THS Settle time is the interval during which HS receiver should
+ * ignore any data lane HS transitions, starting from the beginning
+ * of THS-PREPARE.
+ *
+ * Per DPHY specification, T-HS-SETTLE should be between 85ns + 6UI
+ * and 145ns+10UI.
+ * 85ns + 6UI < (Ths-settle-prog + 5) * lp_clk_period < 145ns + 10UI
+ * midpoint = 115ns + 8UI
+ */
+ if (pix_clk_mhz)
+ *ths_settle_time = (115 * cil_clk_mhz + 8000 * cil_clk_mhz
+ / (2 * pix_clk_mhz) - 5000) / 1000;
+}
+
static int tegra_csi_s_stream(struct v4l2_subdev *subdev, int enable)
{
struct tegra_vi_channel *chan = v4l2_get_subdev_hostdata(subdev);
diff --git a/drivers/staging/media/tegra-video/csi.h b/drivers/staging/media/tegra-video/csi.h
index 0d50fc3..c65ff73 100644
--- a/drivers/staging/media/tegra-video/csi.h
+++ b/drivers/staging/media/tegra-video/csi.h
@@ -51,6 +51,7 @@ struct tegra_csi;
* @h_blank: horizontal blanking for TPG active format
* @v_blank: vertical blanking for TPG active format
* @mipi: mipi device for corresponding csi channel pads
+ * @pixel_rate: active pixel rate from the sensor on this channel
*/
struct tegra_csi_channel {
struct list_head list;
@@ -67,6 +68,7 @@ struct tegra_csi_channel {
unsigned int h_blank;
unsigned int v_blank;
struct tegra_mipi_device *mipi;
+ unsigned int pixel_rate;
};

/**
@@ -147,4 +149,7 @@ extern const struct tegra_csi_soc tegra210_csi_soc;
#endif

void tegra_csi_error_recover(struct v4l2_subdev *subdev);
+void tegra_csi_calc_settle_time(struct tegra_csi_channel *csi_chan,
+ u8 *clk_settle_time,
+ u8 *ths_settle_time);
#endif
diff --git a/drivers/staging/media/tegra-video/tegra210.c b/drivers/staging/media/tegra-video/tegra210.c
index 4f5080a..bcc0492 100644
--- a/drivers/staging/media/tegra-video/tegra210.c
+++ b/drivers/staging/media/tegra-video/tegra210.c
@@ -7,6 +7,7 @@
* This source file contains Tegra210 supported video formats,
* VI and CSI SoC specific data, operations and registers accessors.
*/
+#include <linux/bitfield.h>
#include <linux/clk.h>
#include <linux/clk/tegra.h>
#include <linux/delay.h>
@@ -98,6 +99,8 @@
#define BRICK_CLOCK_B_4X (0x2 << 16)
#define TEGRA_CSI_CIL_PAD_CONFIG1 0x004
#define TEGRA_CSI_CIL_PHY_CONTROL 0x008
+#define CLK_SETTLE_MASK GENMASK(13, 8)
+#define THS_SETTLE_MASK GENMASK(5, 0)
#define TEGRA_CSI_CIL_INTERRUPT_MASK 0x00c
#define TEGRA_CSI_CIL_STATUS 0x010
#define TEGRA_CSI_CILX_STATUS 0x014
@@ -770,8 +773,14 @@ static int tegra210_csi_start_streaming(struct tegra_csi_channel *csi_chan)
{
struct tegra_csi *csi = csi_chan->csi;
unsigned int portno = csi_chan->csi_port_num;
+ u8 clk_settle_time = 0;
+ u8 ths_settle_time = 10;
u32 val;

+ if (!csi_chan->pg_mode)
+ tegra_csi_calc_settle_time(csi_chan, &clk_settle_time,
+ &ths_settle_time);
+
csi_write(csi, portno, TEGRA_CSI_CLKEN_OVERRIDE, 0);

/* clean up status */
@@ -782,7 +791,9 @@ static int tegra210_csi_start_streaming(struct tegra_csi_channel *csi_chan)

/* CIL PHY registers setup */
cil_write(csi, portno, TEGRA_CSI_CIL_PAD_CONFIG0, 0x0);
- cil_write(csi, portno, TEGRA_CSI_CIL_PHY_CONTROL, 0xa);
+ cil_write(csi, portno, TEGRA_CSI_CIL_PHY_CONTROL,
+ FIELD_PREP(CLK_SETTLE_MASK, clk_settle_time) |
+ FIELD_PREP(THS_SETTLE_MASK, ths_settle_time));

/*
* The CSI unit provides for connection of up to six cameras in
@@ -801,7 +812,9 @@ static int tegra210_csi_start_streaming(struct tegra_csi_channel *csi_chan)
BRICK_CLOCK_A_4X);
cil_write(csi, portno + 1, TEGRA_CSI_CIL_PAD_CONFIG0, 0x0);
cil_write(csi, portno + 1, TEGRA_CSI_CIL_INTERRUPT_MASK, 0x0);
- cil_write(csi, portno + 1, TEGRA_CSI_CIL_PHY_CONTROL, 0xa);
+ cil_write(csi, portno + 1, TEGRA_CSI_CIL_PHY_CONTROL,
+ FIELD_PREP(CLK_SETTLE_MASK, clk_settle_time) |
+ FIELD_PREP(THS_SETTLE_MASK, ths_settle_time));
csi_write(csi, portno, TEGRA_CSI_PHY_CIL_COMMAND,
CSI_A_PHY_CIL_ENABLE | CSI_B_PHY_CIL_ENABLE);
} else {
--
2.7.4