media: ov5640: Adjust the clock based on the expected rate

The clock structure for the PCLK is quite obscure in the documentation, and
was hardcoded through the bytes array of each and every mode.

This is troublesome, since we cannot adjust it at runtime based on other
parameters (such as the number of bytes per pixel), and we can't support
either framerates that have not been used by the various vendors, since we
don't have the needed initialization sequence.

We can however understand how the clock tree works, and then implement some
functions to derive the various parameters from a given rate. And now that
those parameters are calculated at runtime, we can remove them from the
initialization sequence.

The modes also gained a new parameter which is the clock that they are
running at, from the register writes they were doing, so for now the switch
to the new algorithm should be transparent.
Co-Developed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Tested-by: Adam Ford <aford173@gmail.com> #imx6dq
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/i2c/ov5640.c

@@ -176,6 +176,7 @@ struct ov5640_mode_info {
 	u32 htot;
 	u32 vact;
 	u32 vtot;
+	u32 pixel_clock;
 	const struct reg_value *reg_data;
 	u32 reg_data_size;
 };
@@ -701,6 +702,7 @@ static const struct reg_value ov5640_setting_15fps_QSXGA_2592_1944[] = {
 /* power-on sensor init reg table */
 static const struct ov5640_mode_info ov5640_mode_init_data = {
 	0, SUBSAMPLING, 640, 1896, 480, 984,
+	56000000,
 	ov5640_init_setting_30fps_VGA,
 	ARRAY_SIZE(ov5640_init_setting_30fps_VGA),
 };
@@ -710,74 +712,91 @@ ov5640_mode_data[OV5640_NUM_FRAMERATES][OV5640_NUM_MODES] = {
 	{
 		{OV5640_MODE_QCIF_176_144, SUBSAMPLING,
 		 176, 1896, 144, 984,
+		 28000000,
 		 ov5640_setting_15fps_QCIF_176_144,
 		 ARRAY_SIZE(ov5640_setting_15fps_QCIF_176_144)},
 		{OV5640_MODE_QVGA_320_240, SUBSAMPLING,
 		 320, 1896, 240, 984,
+		 28000000,
 		 ov5640_setting_15fps_QVGA_320_240,
 		 ARRAY_SIZE(ov5640_setting_15fps_QVGA_320_240)},
 		{OV5640_MODE_VGA_640_480, SUBSAMPLING,
 		 640, 1896, 480, 1080,
+		 28000000,
 		 ov5640_setting_15fps_VGA_640_480,
 		 ARRAY_SIZE(ov5640_setting_15fps_VGA_640_480)},
 		{OV5640_MODE_NTSC_720_480, SUBSAMPLING,
 		 720, 1896, 480, 984,
+		 28000000,
 		 ov5640_setting_15fps_NTSC_720_480,
 		 ARRAY_SIZE(ov5640_setting_15fps_NTSC_720_480)},
 		{OV5640_MODE_PAL_720_576, SUBSAMPLING,
 		 720, 1896, 576, 984,
+		 28000000,
 		 ov5640_setting_15fps_PAL_720_576,
 		 ARRAY_SIZE(ov5640_setting_15fps_PAL_720_576)},
 		{OV5640_MODE_XGA_1024_768, SUBSAMPLING,
 		 1024, 1896, 768, 1080,
+		 28000000,
 		 ov5640_setting_15fps_XGA_1024_768,
 		 ARRAY_SIZE(ov5640_setting_15fps_XGA_1024_768)},
 		{OV5640_MODE_720P_1280_720, SUBSAMPLING,
 		 1280, 1892, 720, 740,
+		 21000000,
 		 ov5640_setting_15fps_720P_1280_720,
 		 ARRAY_SIZE(ov5640_setting_15fps_720P_1280_720)},
 		{OV5640_MODE_1080P_1920_1080, SCALING,
 		 1920, 2500, 1080, 1120,
+		 42000000,
 		 ov5640_setting_15fps_1080P_1920_1080,
 		 ARRAY_SIZE(ov5640_setting_15fps_1080P_1920_1080)},
 		{OV5640_MODE_QSXGA_2592_1944, SCALING,
 		 2592, 2844, 1944, 1968,
+		 84000000,
 		 ov5640_setting_15fps_QSXGA_2592_1944,
 		 ARRAY_SIZE(ov5640_setting_15fps_QSXGA_2592_1944)},
 	}, {
 		{OV5640_MODE_QCIF_176_144, SUBSAMPLING,
 		 176, 1896, 144, 984,
+		 56000000,
 		 ov5640_setting_30fps_QCIF_176_144,
 		 ARRAY_SIZE(ov5640_setting_30fps_QCIF_176_144)},
 		{OV5640_MODE_QVGA_320_240, SUBSAMPLING,
 		 320, 1896, 240, 984,
+		 56000000,
 		 ov5640_setting_30fps_QVGA_320_240,
 		 ARRAY_SIZE(ov5640_setting_30fps_QVGA_320_240)},
 		{OV5640_MODE_VGA_640_480, SUBSAMPLING,
 		 640, 1896, 480, 1080,
+		 56000000,
 		 ov5640_setting_30fps_VGA_640_480,
 		 ARRAY_SIZE(ov5640_setting_30fps_VGA_640_480)},
 		{OV5640_MODE_NTSC_720_480, SUBSAMPLING,
 		 720, 1896, 480, 984,
+		 56000000,
 		 ov5640_setting_30fps_NTSC_720_480,
 		 ARRAY_SIZE(ov5640_setting_30fps_NTSC_720_480)},
 		{OV5640_MODE_PAL_720_576, SUBSAMPLING,
 		 720, 1896, 576, 984,
+		 56000000,
 		 ov5640_setting_30fps_PAL_720_576,
 		 ARRAY_SIZE(ov5640_setting_30fps_PAL_720_576)},
 		{OV5640_MODE_XGA_1024_768, SUBSAMPLING,
 		 1024, 1896, 768, 1080,
+		 56000000,
 		 ov5640_setting_30fps_XGA_1024_768,
 		 ARRAY_SIZE(ov5640_setting_30fps_XGA_1024_768)},
 		{OV5640_MODE_720P_1280_720, SUBSAMPLING,
 		 1280, 1892, 720, 740,
+		 42000000,
 		 ov5640_setting_30fps_720P_1280_720,
 		 ARRAY_SIZE(ov5640_setting_30fps_720P_1280_720)},
 		{OV5640_MODE_1080P_1920_1080, SCALING,
 		 1920, 2500, 1080, 1120,
+		 84000000,
 		 ov5640_setting_30fps_1080P_1920_1080,
 		 ARRAY_SIZE(ov5640_setting_30fps_1080P_1920_1080)},
-		{OV5640_MODE_QSXGA_2592_1944, -1, 0, 0, 0, 0, NULL, 0},
+		{OV5640_MODE_QSXGA_2592_1944, -1, 0, 0, 0, 0, 0, NULL, 0},
 	},
 };
 
@@ -910,6 +929,333 @@ static int ov5640_mod_reg(struct ov5640_dev *sensor, u16 reg,
 	return ov5640_write_reg(sensor, reg, val);
 }
 
+/*
+ * After trying the various combinations, reading various
+ * documentations spreaded around the net, and from the various
+ * feedback, the clock tree is probably as follows:
+ *
+ *   +--------------+
+ *   |  Ext. Clock  |
+ *   +-+------------+
+ *     |  +----------+
+ *     +->|   PLL1   | - reg 0x3036, for the multiplier
+ *        +-+--------+ - reg 0x3037, bits 0-3 for the pre-divider
+ *          |  +--------------+
+ *          +->| System Clock |  - reg 0x3035, bits 4-7
+ *             +-+------------+
+ *               |  +--------------+
+ *               +->| MIPI Divider | - reg 0x3035, bits 0-3
+ *               |  +-+------------+
+ *               |    +----------------> MIPI SCLK
+ *               |    +  +-----+
+ *               |    +->| / 2 |-------> MIPI BIT CLK
+ *               |       +-----+
+ *               |  +--------------+
+ *               +->| PLL Root Div | - reg 0x3037, bit 4
+ *                  +-+------------+
+ *                    |  +---------+
+ *                    +->| Bit Div | - reg 0x3035, bits 0-3
+ *                       +-+-------+
+ *                         |  +-------------+
+ *                         +->| SCLK Div    | - reg 0x3108, bits 0-1
+ *                         |  +-+-----------+
+ *                         |    +---------------> SCLK
+ *                         |  +-------------+
+ *                         +->| SCLK 2X Div | - reg 0x3108, bits 2-3
+ *                         |  +-+-----------+
+ *                         |    +---------------> SCLK 2X
+ *                         |  +-------------+
+ *                         +->| PCLK Div    | - reg 0x3108, bits 4-5
+ *                            ++------------+
+ *                             +  +-----------+
+ *                             +->|   P_DIV   | - reg 0x3035, bits 0-3
+ *                                +-----+-----+
+ *                                       +------------> 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:
+ *  - 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.
+ */
+
+/*
+ * This is supposed to be ranging from 1 to 8, but the value is always
+ * set to 3 in the vendor kernels.
+ */
+#define OV5640_PLL_PREDIV	3
+
+#define OV5640_PLL_MULT_MIN	4
+#define OV5640_PLL_MULT_MAX	252
+
+/*
+ * This is supposed to be ranging from 1 to 16, but the value is
+ * always set to either 1 or 2 in the vendor kernels.
+ */
+#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.
+ */
+#define OV5640_PLL_ROOT_DIV			2
+#define OV5640_PLL_CTRL3_PLL_ROOT_DIV_2		BIT(4)
+
+/*
+ * We only supports 8-bit formats at the moment
+ */
+#define OV5640_BIT_DIV				2
+#define OV5640_PLL_CTRL0_MIPI_MODE_8BIT		0x08
+
+/*
+ * This is supposed to be ranging from 1 to 8, but the value is always
+ * set to 2 in the vendor kernels.
+ */
+#define OV5640_SCLK_ROOT_DIV	2
+
+/*
+ * This is hardcoded so that the consistency is maintained between SCLK and
+ * SCLK 2x.
+ */
+#define OV5640_SCLK2X_ROOT_DIV (OV5640_SCLK_ROOT_DIV / 2)
+
+/*
+ * This is supposed to be ranging from 1 to 8, but the value is always
+ * set to 1 in the vendor kernels.
+ */
+#define OV5640_PCLK_ROOT_DIV			1
+#define OV5640_PLL_SYS_ROOT_DIVIDER_BYPASS	0x00
+
+static unsigned long ov5640_compute_sys_clk(struct ov5640_dev *sensor,
+					    u8 pll_prediv, u8 pll_mult,
+					    u8 sysdiv)
+{
+	unsigned long sysclk = sensor->xclk_freq / pll_prediv * pll_mult;
+
+	/* PLL1 output cannot exceed 1GHz. */
+	if (sysclk / 1000000 > 1000)
+		return 0;
+
+	return sysclk / sysdiv;
+}
+
+static unsigned long ov5640_calc_sys_clk(struct ov5640_dev *sensor,
+					 unsigned long rate,
+					 u8 *pll_prediv, u8 *pll_mult,
+					 u8 *sysdiv)
+{
+	unsigned long best = ~0;
+	u8 best_sysdiv = 1, best_mult = 1;
+	u8 _sysdiv, _pll_mult;
+
+	for (_sysdiv = OV5640_SYSDIV_MIN;
+	     _sysdiv <= OV5640_SYSDIV_MAX;
+	     _sysdiv++) {
+		for (_pll_mult = OV5640_PLL_MULT_MIN;
+		     _pll_mult <= OV5640_PLL_MULT_MAX;
+		     _pll_mult++) {
+			unsigned long _rate;
+
+			/*
+			 * The PLL multiplier cannot be odd if above
+			 * 127.
+			 */
+			if (_pll_mult > 127 && (_pll_mult % 2))
+				continue;
+
+			_rate = ov5640_compute_sys_clk(sensor,
+						       OV5640_PLL_PREDIV,
+						       _pll_mult, _sysdiv);
+
+			/*
+			 * We have reached the maximum allowed PLL1 output,
+			 * increase sysdiv.
+			 */
+			if (!rate)
+				break;
+
+			/*
+			 * Prefer rates above the expected clock rate than
+			 * below, even if that means being less precise.
+			 */
+			if (_rate < rate)
+				continue;
+
+			if (abs(rate - _rate) < abs(rate - best)) {
+				best = _rate;
+				best_sysdiv = _sysdiv;
+				best_mult = _pll_mult;
+			}
+
+			if (_rate == rate)
+				goto out;
+		}
+	}
+
+out:
+	*sysdiv = best_sysdiv;
+	*pll_prediv = OV5640_PLL_PREDIV;
+	*pll_mult = best_mult;
+
+	return best;
+}
+
+/*
+ * 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)
+{
+	const struct ov5640_mode_info *mode = sensor->current_mode;
+	u8 prediv, mult, sysdiv;
+	u8 mipi_div;
+	int ret;
+
+	/*
+	 * 1280x720 is reported to use 'SUBSAMPLING' only,
+	 * but according to the sensor manual it goes through the
+	 * scaler before subsampling.
+	 */
+	if (mode->dn_mode == SCALING ||
+	   (mode->id == OV5640_MODE_720P_1280_720))
+		mipi_div = OV5640_MIPI_DIV_SCLK;
+	else
+		mipi_div = OV5640_MIPI_DIV_PCLK;
+
+	ov5640_calc_sys_clk(sensor, rate, &prediv, &mult, &sysdiv);
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL0,
+			     0x0f, OV5640_PLL_CTRL0_MIPI_MODE_8BIT);
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL1,
+			     0xff, sysdiv << 4 | mipi_div);
+	if (ret)
+		return ret;
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL2, 0xff, mult);
+	if (ret)
+		return ret;
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL3,
+			     0x1f, OV5640_PLL_CTRL3_PLL_ROOT_DIV_2 | prediv);
+	if (ret)
+		return ret;
+
+	return ov5640_mod_reg(sensor, OV5640_REG_SYS_ROOT_DIVIDER,
+			      0x30, OV5640_PLL_SYS_ROOT_DIVIDER_BYPASS);
+}
+
+static unsigned long ov5640_calc_pclk(struct ov5640_dev *sensor,
+				      unsigned long rate,
+				      u8 *pll_prediv, u8 *pll_mult, u8 *sysdiv,
+				      u8 *pll_rdiv, u8 *bit_div, u8 *pclk_div)
+{
+	unsigned long _rate = rate * OV5640_PLL_ROOT_DIV * OV5640_BIT_DIV *
+				OV5640_PCLK_ROOT_DIV;
+
+	_rate = ov5640_calc_sys_clk(sensor, _rate, pll_prediv, pll_mult,
+				    sysdiv);
+	*pll_rdiv = OV5640_PLL_ROOT_DIV;
+	*bit_div = OV5640_BIT_DIV;
+	*pclk_div = OV5640_PCLK_ROOT_DIV;
+
+	return _rate / *pll_rdiv / *bit_div / *pclk_div;
+}
+
+static int ov5640_set_dvp_pclk(struct ov5640_dev *sensor, unsigned long rate)
+{
+	u8 prediv, mult, sysdiv, pll_rdiv, bit_div, pclk_div;
+	int ret;
+
+	ov5640_calc_pclk(sensor, rate, &prediv, &mult, &sysdiv, &pll_rdiv,
+			 &bit_div, &pclk_div);
+
+	if (bit_div == 2)
+		bit_div = 8;
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL0,
+			     0x0f, bit_div);
+	if (ret)
+		return ret;
+
+	/*
+	 * We need to set sysdiv according to the clock, and to clear
+	 * the MIPI divider.
+	 */
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL1,
+			     0xff, sysdiv << 4);
+	if (ret)
+		return ret;
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL2,
+			     0xff, mult);
+	if (ret)
+		return ret;
+
+	ret = ov5640_mod_reg(sensor, OV5640_REG_SC_PLL_CTRL3,
+			     0x1f, prediv | ((pll_rdiv - 1) << 4));
+	if (ret)
+		return ret;
+
+	return ov5640_mod_reg(sensor, OV5640_REG_SYS_ROOT_DIVIDER, 0x30,
+			      (ilog2(pclk_div) << 4));
+}
+
 /* download ov5640 settings to sensor through i2c */
 static int ov5640_set_timings(struct ov5640_dev *sensor,
 			      const struct ov5640_mode_info *mode)
@@ -1638,6 +1984,7 @@ 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;
@@ -1656,6 +2003,22 @@ 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 = mode->pixel_clock * 16;
+	if (sensor->ep.bus_type == V4L2_MBUS_CSI2_DPHY) {
+		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 (ret < 0)
+		return 0;
+
 	if ((dn_mode == SUBSAMPLING && orig_dn_mode == SCALING) ||
 	    (dn_mode == SCALING && orig_dn_mode == SUBSAMPLING)) {
 		/*