On Thu May 22 16:35:06 2025 +0200, Mathis Foerst wrote:
> The MT9M114 sensor has an internal PLL that generates the required SYSCLK
> from EXTCLK. It also has the option to bypass the PLL and use EXTCLK
> directly as SYSCLK.
> The current driver implementation uses a hardcoded PLL configuration that
> requires a specific EXTCLK frequency. Depending on the available clocks,
> it can be desirable to use a different PLL configuration or to bypass it.
>
> The link-frequency of the output bus (Parallel or MIPI-CSI) is configured
> in the device tree.
>
> Check if EXTCLK can be used as SYSCLK to achieve this link-frequency. If
> yes, bypass the PLL.
> Otherwise, (as before) check if EXTCLK and the default PLL configuration
> provide the required SYSCLK to achieve the link-frequency. If yes, use the
> PLL. If no, throw an error.
>
> Signed-off-by: Mathis Foerst <mathis.foe...@mt.com>
> Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>
> Signed-off-by: Sakari Ailus <sakari.ai...@linux.intel.com>
> Signed-off-by: Hans Verkuil <hverk...@xs4all.nl>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/i2c/mt9m114.c | 68 +++++++++++++++++++++++++++++++++------------
1 file changed, 50 insertions(+), 18 deletions(-)
---
diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index 5f0b0ad8f885..c3ec2eb0b134 100644
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -261,6 +261,7 @@
#define MT9M114_CAM_PGA_PGA_CONTROL CCI_REG16(0xc95e)
#define MT9M114_CAM_SYSCTL_PLL_ENABLE CCI_REG8(0xc97e)
#define MT9M114_CAM_SYSCTL_PLL_ENABLE_VALUE BIT(0)
+#define MT9M114_CAM_SYSCTL_PLL_DISABLE_VALUE 0x00
#define MT9M114_CAM_SYSCTL_PLL_DIVIDER_M_N CCI_REG16(0xc980)
#define MT9M114_CAM_SYSCTL_PLL_DIVIDER_VALUE(m, n) (((n) << 8) |
(m))
#define MT9M114_CAM_SYSCTL_PLL_DIVIDER_P CCI_REG16(0xc982)
@@ -377,6 +378,7 @@ struct mt9m114 {
struct gpio_desc *reset;
struct regulator_bulk_data supplies[3];
struct v4l2_fwnode_endpoint bus_cfg;
+ bool bypass_pll;
struct {
unsigned int m;
@@ -743,14 +745,21 @@ static int mt9m114_initialize(struct mt9m114 *sensor)
}
/* Configure the PLL. */
- cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_ENABLE,
- MT9M114_CAM_SYSCTL_PLL_ENABLE_VALUE, &ret);
- cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_DIVIDER_M_N,
- MT9M114_CAM_SYSCTL_PLL_DIVIDER_VALUE(sensor->pll.m,
- sensor->pll.n),
- &ret);
- cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_DIVIDER_P,
- MT9M114_CAM_SYSCTL_PLL_DIVIDER_P_VALUE(sensor->pll.p), &ret);
+ if (sensor->bypass_pll) {
+ cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_ENABLE,
+ MT9M114_CAM_SYSCTL_PLL_DISABLE_VALUE, &ret);
+ } else {
+ cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_ENABLE,
+ MT9M114_CAM_SYSCTL_PLL_ENABLE_VALUE, &ret);
+ cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_DIVIDER_M_N,
+ MT9M114_CAM_SYSCTL_PLL_DIVIDER_VALUE(sensor->pll.m,
+ sensor->pll.n),
+ &ret);
+ cci_write(sensor->regmap, MT9M114_CAM_SYSCTL_PLL_DIVIDER_P,
+ MT9M114_CAM_SYSCTL_PLL_DIVIDER_P_VALUE(sensor->pll.p),
+ &ret);
+ }
+
cci_write(sensor->regmap, MT9M114_CAM_SENSOR_CFG_PIXCLK,
sensor->pixrate, &ret);
@@ -2235,9 +2244,22 @@ static const struct dev_pm_ops mt9m114_pm_ops = {
* Probe & Remove
*/
+static int mt9m114_verify_link_frequency(struct mt9m114 *sensor,
+ unsigned int pixrate)
+{
+ unsigned int link_freq = sensor->bus_cfg.bus_type == V4L2_MBUS_CSI2_DPHY
+ ? pixrate * 8 : pixrate * 2;
+
+ if (sensor->bus_cfg.nr_of_link_frequencies != 1 ||
+ sensor->bus_cfg.link_frequencies[0] != link_freq)
+ return -EINVAL;
+
+ return 0;
+}
+
static int mt9m114_clk_init(struct mt9m114 *sensor)
{
- unsigned int link_freq;
+ unsigned int pixrate;
/* Hardcode the PLL multiplier and dividers to default settings. */
sensor->pll.m = 32;
@@ -2249,19 +2271,29 @@ static int mt9m114_clk_init(struct mt9m114 *sensor)
* for 16-bit per pixel, transmitted in DDR over a single lane. For
* parallel mode, the sensor ouputs one pixel in two PIXCLK cycles.
*/
- sensor->pixrate = clk_get_rate(sensor->clk) * sensor->pll.m
- / ((sensor->pll.n + 1) * (sensor->pll.p + 1));
- link_freq = sensor->bus_cfg.bus_type == V4L2_MBUS_CSI2_DPHY
- ? sensor->pixrate * 8 : sensor->pixrate * 2;
+ /*
+ * Check if EXTCLK fits the configured link frequency. Bypass the PLL
+ * in this case.
+ */
+ pixrate = clk_get_rate(sensor->clk) / 2;
+ if (mt9m114_verify_link_frequency(sensor, pixrate) == 0) {
+ sensor->pixrate = pixrate;
+ sensor->bypass_pll = true;
+ return 0;
+ }
- if (sensor->bus_cfg.nr_of_link_frequencies != 1 ||
- sensor->bus_cfg.link_frequencies[0] != link_freq) {
- dev_err(&sensor->client->dev, "Unsupported DT
link-frequencies\n");
- return -EINVAL;
+ /* Check if the PLL configuration fits the configured link frequency. */
+ pixrate = clk_get_rate(sensor->clk) * sensor->pll.m
+ / ((sensor->pll.n + 1) * (sensor->pll.p + 1));
+ if (mt9m114_verify_link_frequency(sensor, pixrate) == 0) {
+ sensor->pixrate = pixrate;
+ sensor->bypass_pll = false;
+ return 0;
}
- return 0;
+ dev_err(&sensor->client->dev, "Unsupported DT link-frequencies\n");
+ return -EINVAL;
}
static int mt9m114_identify(struct mt9m114 *sensor)
