[PATCH v7 07/28] media: ov5640: Rework CSI-2 clock tree

Sakari Ailus
2022-05-13T14:16:17Z

Re-work the ov5640_set_mipi_pclk() function to calculate the
PLL configuration using the pixel_rate and link_freq values set at
s_fmt time.

Rework the DVP clock mode settings to calculate the pixel clock
internally and remove the assumption on the 16bpp format.

Tested in MIPI CSI-2 mode with 1 and 2 data lanes with:
- all the sensor supported resolutions in UYVY, RGB565 and MJPEG formats.
- resolutions >= 1280x720 in RAW Bayer format.
- resolutions < 1280x720 in RGB888 format.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Acked-by: Hugues Fruchet <hugues.fruchet@foss.st.com>
Tested-by: Hugues Fruchet <hugues.fruchet@foss.st.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

[Rework pclk_period and link_freq computation]
Signed-off-by: Hugues Fruchet <hugues.fruchet@st.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
drivers/media/i2c/ov5640.c | 208 +++++++++++++++++++------------------
1 file changed, 108 insertions(+), 100 deletions(-)

diff --git a/drivers/media/i2c/ov5640.c b/drivers/media/i2c/ov5640.c
index 5d7383369a4cc..1f439f7692746 100644
--- a/drivers/media/i2c/ov5640.c
+++ b/drivers/media/i2c/ov5640.c
@@ -90,6 +90,7 @@
#define OV5640_REG_POLARITY_CTRL00 0x4740
#define OV5640_REG_MIPI_CTRL00 0x4800
#define OV5640_REG_DEBUG_MODE 0x4814
+#define OV5640_REG_PCLK_PERIOD 0x4837
#define OV5640_REG_ISP_FORMAT_MUX_CTRL 0x501f
#define OV5640_REG_PRE_ISP_TEST_SET1 0x503d
#define OV5640_REG_SDE_CTRL0 0x5580
@@ -354,6 +355,18 @@ static inline bool ov5640_is_csi2(const struct ov5640_dev *sensor)
return sensor->ep.bus_type == V4L2_MBUS_CSI2_DPHY;
}

+static u32 ov5640_code_to_bpp(u32 code)
+{
+ unsigned int i;
+
+ for (i = 0; i < ARRAY_SIZE(ov5640_formats); ++i) {
+ if (ov5640_formats[i].code == code)
+ return ov5640_formats[i].bpp;
+ }
+
+ return 0;
+}
+
/*
* FIXME: all of these register tables are likely filled with
* entries that set the register to their power-on default values,
@@ -914,20 +927,10 @@ static int ov5640_mod_reg(struct ov5640_dev *sensor, u16 reg,
* +-----+-----+
* +------------> PCLK
*
- * This is deviating from the datasheet at least for the register
- * 0x3108, since it's said here that the PCLK would be clocked from
- * the PLL.
- *
- * There seems to be also (unverified) constraints:
+ * There seems to be also constraints:
* - the PLL pre-divider output rate should be in the 4-27MHz range
* - the PLL multiplier output rate should be in the 500-1000MHz range
* - PCLK >= SCLK * 2 in YUV, >= SCLK in Raw or JPEG
- *
- * In the two latter cases, these constraints are met since our
- * factors are hardcoded. If we were to change that, we would need to
- * take this into account. The only varying parts are the PLL
- * multiplier and the system clock divider, which are shared between
- * all these clocks so won't cause any issue.
*/

/*
@@ -946,13 +949,6 @@ static int ov5640_mod_reg(struct ov5640_dev *sensor, u16 reg,
#define OV5640_SYSDIV_MIN 1
#define OV5640_SYSDIV_MAX 16

-/*
- * Hardcode these values for scaler and non-scaler modes.
- * FIXME: to be re-calcualted for 1 data lanes setups
- */
-#define OV5640_MIPI_DIV_PCLK 2
-#define OV5640_MIPI_DIV_SCLK 1
-
/*
* This is supposed to be ranging from 1 to 2, but the value is always
* set to 2 in the vendor kernels.
@@ -1062,70 +1058,83 @@ static unsigned long ov5640_calc_sys_clk(struct ov5640_dev *sensor,
/*
* ov5640_set_mipi_pclk() - Calculate the clock tree configuration values
* for the MIPI CSI-2 output.
- *
- * @rate: The requested bandwidth per lane in bytes per second.
- * 'Bandwidth Per Lane' is calculated as:
- * bpl = HTOT * VTOT * FPS * bpp / num_lanes;
- *
- * This function use the requested bandwidth to calculate:
- * - sample_rate = bpl / (bpp / num_lanes);
- * = bpl / (PLL_RDIV * BIT_DIV * PCLK_DIV * MIPI_DIV / num_lanes);
- *
- * - mipi_sclk = bpl / MIPI_DIV / 2; ( / 2 is for CSI-2 DDR)
- *
- * with these fixed parameters:
- * PLL_RDIV = 2;
- * BIT_DIVIDER = 2; (MIPI_BIT_MODE == 8 ? 2 : 2,5);
- * PCLK_DIV = 1;
- *
- * The MIPI clock generation differs for modes that use the scaler and modes
- * that do not. In case the scaler is in use, the MIPI_SCLK generates the MIPI
- * BIT CLk, and thus:
- *
- * - mipi_sclk = bpl / MIPI_DIV / 2;
- * MIPI_DIV = 1;
- *
- * For modes that do not go through the scaler, the MIPI BIT CLOCK is generated
- * from the pixel clock, and thus:
- *
- * - sample_rate = bpl / (bpp / num_lanes);
- * = bpl / (2 * 2 * 1 * MIPI_DIV / num_lanes);
- * = bpl / (4 * MIPI_DIV / num_lanes);
- * - MIPI_DIV = bpp / (4 * num_lanes);
- *
- * FIXME: this have been tested with 16bpp and 2 lanes setup only.
- * MIPI_DIV is fixed to value 2, but it -might- be changed according to the
- * above formula for setups with 1 lane or image formats with different bpp.
- *
- * FIXME: this deviates from the sensor manual documentation which is quite
- * thin on the MIPI clock tree generation part.
*/
-static int ov5640_set_mipi_pclk(struct ov5640_dev *sensor,
- unsigned long rate)
+static int ov5640_set_mipi_pclk(struct ov5640_dev *sensor)
{
- const struct ov5640_mode_info *mode = sensor->current_mode;
+ u8 bit_div, mipi_div, pclk_div, sclk_div, sclk2x_div, root_div;
u8 prediv, mult, sysdiv;
- u8 mipi_div;
+ unsigned long link_freq;
+ unsigned long sysclk;
+ u8 pclk_period;
+ u32 sample_rate;
+ u32 num_lanes;
int ret;

+ /* Use the link freq computed at ov5640_update_pixel_rate() time. */
+ link_freq = sensor->current_link_freq;
+
/*
- * 1280x720 is reported to use 'SUBSAMPLING' only,
- * but according to the sensor manual it goes through the
- * scaler before subsampling.
+ * - mipi_div - Additional divider for the MIPI lane clock.
+ *
+ * Higher link frequencies would make sysclk > 1GHz.
+ * Keep the sysclk low and do not divide in the MIPI domain.
*/
- if (mode->dn_mode == SCALING ||
- (mode->id == OV5640_MODE_720P_1280_720))
- mipi_div = OV5640_MIPI_DIV_SCLK;
+ if (link_freq > OV5640_LINK_RATE_MAX)
+ mipi_div = 1;
else
- mipi_div = OV5640_MIPI_DIV_PCLK;
+ mipi_div = 2;

- ov5640_calc_sys_clk(sensor, rate, &prediv, &mult, &sysdiv);
+ sysclk = link_freq * mipi_div;
+ ov5640_calc_sys_clk(sensor, sysclk, &prediv, &mult, &sysdiv);

- ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL0,
- 0x0f, OV5640_PLL_CTRL0_MIPI_MODE_8BIT);
+ /*
+ * Adjust PLL parameters to maintain the MIPI_SCLK-to-PCLK ratio.
+ *
+ * - root_div = 2 (fixed)
+ * - bit_div : MIPI 8-bit = 2; MIPI 10-bit = 2.5
+ * - pclk_div = 1 (fixed)
+ * - p_div = (2 lanes ? mipi_div : 2 * mipi_div)
+ *
+ * This results in the following MIPI_SCLK depending on the number
+ * of lanes:
+ *
+ * - 2 lanes: MIPI_SCLK = (4 or 5) * PCLK
+ * - 1 lanes: MIPI_SCLK = (8 or 10) * PCLK
+ */
+ root_div = OV5640_PLL_CTRL3_PLL_ROOT_DIV_2;
+ bit_div = OV5640_PLL_CTRL0_MIPI_MODE_8BIT;
+ pclk_div = ilog2(OV5640_PCLK_ROOT_DIV);

- ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL1,
- 0xff, sysdiv << 4 | mipi_div);
+ /*
+ * Scaler clock:
+ * - YUV: PCLK >= 2 * SCLK
+ * - RAW or JPEG: PCLK >= SCLK
+ * - sclk2x_div = sclk_div / 2
+ */
+ sclk_div = ilog2(OV5640_SCLK_ROOT_DIV);
+ sclk2x_div = ilog2(OV5640_SCLK2X_ROOT_DIV);
+
+ /*
+ * Set the pixel clock period expressed in ns with 1-bit decimal
+ * (0x01=0.5ns).
+ *
+ * The register is very briefly documented. In the OV5645 datasheet it
+ * is described as (2 * pclk period), and from testing it seems the
+ * actual definition is 2 * 8-bit sample period.
+ *
+ * 2 * sample_period = (mipi_clk * 2 * num_lanes / bpp) * (bpp / 8) / 2
+ */
+ num_lanes = sensor->ep.bus.mipi_csi2.num_data_lanes;
+ sample_rate = (link_freq * mipi_div * num_lanes * 2) / 16;
+ pclk_period = 2000000000UL / sample_rate;
+
+ /* Program the clock tree registers. */
+ ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL0, 0x0f, bit_div);
+ if (ret)
+ return ret;
+
+ ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL1, 0xff,
+ (sysdiv << 4) | mipi_div);
if (ret)
return ret;

@@ -1133,13 +1142,27 @@ static int ov5640_set_mipi_pclk(struct ov5640_dev *sensor,
if (ret)
return ret;

- ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL3,
- 0x1f, OV5640_PLL_CTRL3_PLL_ROOT_DIV_2 | prediv);
+ ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL3, 0x1f,
+ root_div | prediv);
if (ret)
return ret;

- return ov5640_mod_reg(sensor, OV5640_REG_SYS_ROOT_DIVIDER,
- 0x30, OV5640_PLL_SYS_ROOT_DIVIDER_BYPASS);
+ ret = ov5640_mod_reg(sensor, OV5640_REG_SYS_ROOT_DIVIDER, 0x3f,
+ (pclk_div << 4) | (sclk2x_div << 2) | sclk_div);
+ if (ret)
+ return ret;
+
+ return ov5640_write_reg(sensor, OV5640_REG_PCLK_PERIOD, pclk_period);
+}
+
+static u32 ov5640_calc_pixel_rate(struct ov5640_dev *sensor)
+{
+ u32 rate;
+
+ rate = sensor->current_mode->vtot * sensor->current_mode->htot;
+ rate *= ov5640_framerates[sensor->current_fr];
+
+ return rate;
}

static unsigned long ov5640_calc_pclk(struct ov5640_dev *sensor,
@@ -1159,11 +1182,16 @@ static unsigned long ov5640_calc_pclk(struct ov5640_dev *sensor,
return _rate / *pll_rdiv / *bit_div / *pclk_div;
}

-static int ov5640_set_dvp_pclk(struct ov5640_dev *sensor, unsigned long rate)
+static int ov5640_set_dvp_pclk(struct ov5640_dev *sensor)
{
u8 prediv, mult, sysdiv, pll_rdiv, bit_div, pclk_div;
+ u32 rate;
int ret;

+ rate = ov5640_calc_pixel_rate(sensor);
+ rate *= ov5640_code_to_bpp(sensor->fmt.code);
+ rate /= sensor->ep.bus.parallel.bus_width;
+
ov5640_calc_pclk(sensor, rate, &prediv, &mult, &sysdiv, &pll_rdiv,
&bit_div, &pclk_div);

@@ -1688,16 +1716,6 @@ ov5640_find_mode(struct ov5640_dev *sensor, enum ov5640_frame_rate fr,
return mode;
}

-static u64 ov5640_calc_pixel_rate(struct ov5640_dev *sensor)
-{
- u64 rate;
-
- rate = sensor->current_mode->vtot * sensor->current_mode->htot;
- rate *= ov5640_framerates[sensor->current_fr];
-
- return rate;
-}
-
/*
* sensor changes between scaling and subsampling, go through
* exposure calculation
@@ -1879,7 +1897,6 @@ static int ov5640_set_mode(struct ov5640_dev *sensor)
enum ov5640_downsize_mode dn_mode, orig_dn_mode;
bool auto_gain = sensor->ctrls.auto_gain->val == 1;
bool auto_exp = sensor->ctrls.auto_exp->val == V4L2_EXPOSURE_AUTO;
- unsigned long rate;
int ret;

dn_mode = mode->dn_mode;
@@ -1898,19 +1915,10 @@ static int ov5640_set_mode(struct ov5640_dev *sensor)
goto restore_auto_gain;
}

- /*
- * All the formats we support have 16 bits per pixel, seems to require
- * the same rate than YUV, so we can just use 16 bpp all the time.
- */
- rate = ov5640_calc_pixel_rate(sensor) * 16;
- if (ov5640_is_csi2(sensor)) {
- rate = rate / sensor->ep.bus.mipi_csi2.num_data_lanes;
- ret = ov5640_set_mipi_pclk(sensor, rate);
- } else {
- rate = rate / sensor->ep.bus.parallel.bus_width;
- ret = ov5640_set_dvp_pclk(sensor, rate);
- }
-
+ if (ov5640_is_csi2(sensor))
+ ret = ov5640_set_mipi_pclk(sensor);
+ else
+ ret = ov5640_set_dvp_pclk(sensor);
if (ret < 0)
return 0;

--
2.30.2