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Subject[PATCH v2 1/4] media: atmel: atmel-isc: reworked white balance feature
Date
From: Eugen Hristev <eugen.hristev@microchip.com>

Reworked auto white balance feature (awb) to cope with all four channels.
Implemented stretching and grey world algorithms.
Using the histogram, the ISC will auto adjust the white balance during
frame captures.
Because each histogram needs a frame, it will take 4 frames for one adjustment.
When the gains were updated by previous code, the registers for the gains
were updated only on new streaming start. Now, after each full histogram the
registers are updated with new gains.
Also, on previous code, if the streaming stopped but not all 3 histograms
finished, a new histogram was started either way. This used to lead to an
error "timeout to update profile" when streaming was stopped.
According to the hardware, histogram can only work together with the capture,
not independently.

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
---
drivers/media/platform/atmel/atmel-isc-regs.h | 6 +-
drivers/media/platform/atmel/atmel-isc.c | 200 +++++++++++++++++++++++---
2 files changed, 181 insertions(+), 25 deletions(-)

diff --git a/drivers/media/platform/atmel/atmel-isc-regs.h b/drivers/media/platform/atmel/atmel-isc-regs.h
index 8f7f8ef..c1283fb 100644
--- a/drivers/media/platform/atmel/atmel-isc-regs.h
+++ b/drivers/media/platform/atmel/atmel-isc-regs.h
@@ -100,13 +100,15 @@
#define ISC_WB_O_RGR 0x00000060

/* ISC White Balance Offset for B, GB Register */
-#define ISC_WB_O_BGR 0x00000064
+#define ISC_WB_O_BGB 0x00000064

/* ISC White Balance Gain for R, GR Register */
#define ISC_WB_G_RGR 0x00000068

/* ISC White Balance Gain for B, GB Register */
-#define ISC_WB_G_BGR 0x0000006c
+#define ISC_WB_G_BGB 0x0000006c
+
+#define ISC_WB_O_ZERO_VAL (1 << 13)

/* ISC Color Filter Array Control Register */
#define ISC_CFA_CTRL 0x00000070
diff --git a/drivers/media/platform/atmel/atmel-isc.c b/drivers/media/platform/atmel/atmel-isc.c
index 94cb309..0ac5953 100644
--- a/drivers/media/platform/atmel/atmel-isc.c
+++ b/drivers/media/platform/atmel/atmel-isc.c
@@ -169,13 +169,17 @@ struct isc_ctrls {
u8 gamma_index;
u8 awb;

- u32 r_gain;
- u32 b_gain;
+ /* one for each component : GR, R, GB, B */
+ u32 gain[HIST_BAYER];
+ u32 offset[HIST_BAYER];

u32 hist_entry[HIST_ENTRIES];
u32 hist_count[HIST_BAYER];
u8 hist_id;
u8 hist_stat;
+#define HIST_MIN_INDEX 0
+#define HIST_MAX_INDEX 1
+ u32 hist_minmax[HIST_BAYER][2];
};

#define ISC_PIPE_LINE_NODE_NUM 11
@@ -209,6 +213,7 @@ struct isc_device {
struct work_struct awb_work;

struct mutex lock;
+ spinlock_t awb_lock;

struct regmap_field *pipeline[ISC_PIPE_LINE_NODE_NUM];

@@ -395,6 +400,40 @@ module_param(sensor_preferred, uint, 0644);
MODULE_PARM_DESC(sensor_preferred,
"Sensor is preferred to output the specified format (1-on 0-off), default 1");

+static inline void isc_update_awb_ctrls(struct isc_device *isc)
+{
+ struct isc_ctrls *ctrls = &isc->ctrls;
+
+ regmap_write(isc->regmap, ISC_WB_O_RGR,
+ (ISC_WB_O_ZERO_VAL - (ctrls->offset[ISC_HIS_CFG_MODE_R])) |
+ ((ISC_WB_O_ZERO_VAL - ctrls->offset[ISC_HIS_CFG_MODE_GR]) << 16));
+ regmap_write(isc->regmap, ISC_WB_O_BGB,
+ (ISC_WB_O_ZERO_VAL - (ctrls->offset[ISC_HIS_CFG_MODE_B])) |
+ ((ISC_WB_O_ZERO_VAL - ctrls->offset[ISC_HIS_CFG_MODE_GB]) << 16));
+ regmap_write(isc->regmap, ISC_WB_G_RGR,
+ ctrls->gain[ISC_HIS_CFG_MODE_R] |
+ (ctrls->gain[ISC_HIS_CFG_MODE_GR] << 16));
+ regmap_write(isc->regmap, ISC_WB_G_BGB,
+ ctrls->gain[ISC_HIS_CFG_MODE_B] |
+ (ctrls->gain[ISC_HIS_CFG_MODE_GB] << 16));
+}
+
+static inline void isc_reset_awb_ctrls(struct isc_device *isc)
+{
+ int c;
+
+ for (c = ISC_HIS_CFG_MODE_GR; c <= ISC_HIS_CFG_MODE_B; c++) {
+ /* gains have a fixed point at 9 decimals */
+ isc->ctrls.gain[c] = 1 << 9;
+ /* offsets are in 2's complements, the value
+ * will be substracted from ISC_WB_O_ZERO_VAL to obtain
+ * 2's complement of a value between 0 and
+ * ISC_WB_O_ZERO_VAL >> 1
+ */
+ isc->ctrls.offset[c] = ISC_WB_O_ZERO_VAL;
+ }
+}
+
static int isc_wait_clk_stable(struct clk_hw *hw)
{
struct isc_clk *isc_clk = to_isc_clk(hw);
@@ -775,7 +814,9 @@ static void isc_start_dma(struct isc_device *isc)
dctrl_dview = isc->config.dctrl_dview;

regmap_write(regmap, ISC_DCTRL, dctrl_dview | ISC_DCTRL_IE_IS);
+ spin_lock(&isc->awb_lock);
regmap_write(regmap, ISC_CTRLEN, ISC_CTRL_CAPTURE);
+ spin_unlock(&isc->awb_lock);
}

static void isc_set_pipeline(struct isc_device *isc, u32 pipeline)
@@ -797,11 +838,11 @@ static void isc_set_pipeline(struct isc_device *isc, u32 pipeline)

bay_cfg = isc->config.sd_format->cfa_baycfg;

+ if (!ctrls->awb)
+ isc_reset_awb_ctrls(isc);
+
regmap_write(regmap, ISC_WB_CFG, bay_cfg);
- regmap_write(regmap, ISC_WB_O_RGR, 0x0);
- regmap_write(regmap, ISC_WB_O_BGR, 0x0);
- regmap_write(regmap, ISC_WB_G_RGR, ctrls->r_gain | (0x1 << 25));
- regmap_write(regmap, ISC_WB_G_BGR, ctrls->b_gain | (0x1 << 25));
+ isc_update_awb_ctrls(isc);

regmap_write(regmap, ISC_CFA_CFG, bay_cfg | ISC_CFA_CFG_EITPOL);

@@ -851,13 +892,13 @@ static void isc_set_histogram(struct isc_device *isc, bool enable)

if (enable) {
regmap_write(regmap, ISC_HIS_CFG,
- ISC_HIS_CFG_MODE_R |
+ ISC_HIS_CFG_MODE_GR |
(isc->config.sd_format->cfa_baycfg
<< ISC_HIS_CFG_BAYSEL_SHIFT) |
ISC_HIS_CFG_RAR);
regmap_write(regmap, ISC_HIS_CTRL, ISC_HIS_CTRL_EN);
regmap_write(regmap, ISC_INTEN, ISC_INT_HISDONE);
- ctrls->hist_id = ISC_HIS_CFG_MODE_R;
+ ctrls->hist_id = ISC_HIS_CFG_MODE_GR;
isc_update_profile(isc);
regmap_write(regmap, ISC_CTRLEN, ISC_CTRL_HISREQ);

@@ -900,7 +941,7 @@ static int isc_configure(struct isc_device *isc)
isc_set_pipeline(isc, pipeline);

/*
- * The current implemented histogram is available for RAW R, B, GB
+ * The current implemented histogram is available for RAW R, B, GB, GR
* channels. We need to check if sensor is outputting RAW BAYER
*/
if (isc->ctrls.awb &&
@@ -1475,6 +1516,12 @@ static int isc_set_fmt(struct isc_device *isc, struct v4l2_format *f)
return ret;

isc->fmt = *f;
+
+ if (isc->try_config.sd_format && isc->config.sd_format &&
+ isc->try_config.sd_format != isc->config.sd_format) {
+ isc->ctrls.hist_stat = HIST_INIT;
+ isc_reset_awb_ctrls(isc);
+ }
/* make the try configuration active */
isc->config = isc->try_config;

@@ -1758,7 +1805,7 @@ static irqreturn_t isc_interrupt(int irq, void *dev_id)
return ret;
}

-static void isc_hist_count(struct isc_device *isc)
+static void isc_hist_count(struct isc_device *isc, u32 *min, u32 *max)
{
struct regmap *regmap = isc->regmap;
struct isc_ctrls *ctrls = &isc->ctrls;
@@ -1766,25 +1813,99 @@ static void isc_hist_count(struct isc_device *isc)
u32 *hist_entry = &ctrls->hist_entry[0];
u32 i;

+ *min = 0;
+ *max = HIST_ENTRIES;
+
regmap_bulk_read(regmap, ISC_HIS_ENTRY, hist_entry, HIST_ENTRIES);

*hist_count = 0;
- for (i = 0; i < HIST_ENTRIES; i++)
+ /*
+ * we deliberately ignore the end of the histogram,
+ * the most white pixels
+ */
+ for (i = 1; i < HIST_ENTRIES; i++) {
+ if (*hist_entry && !*min)
+ *min = i;
+ if (*hist_entry)
+ *max = i;
*hist_count += i * (*hist_entry++);
+ }
+
+ if (!*min)
+ *min = 1;
}

static void isc_wb_update(struct isc_ctrls *ctrls)
{
u32 *hist_count = &ctrls->hist_count[0];
- u64 g_count = (u64)hist_count[ISC_HIS_CFG_MODE_GB] << 9;
- u32 hist_r = hist_count[ISC_HIS_CFG_MODE_R];
- u32 hist_b = hist_count[ISC_HIS_CFG_MODE_B];
+ u32 c, offset[4];
+ u64 avg = 0;
+ /* We compute two gains, stretch gain and grey world gain */
+ u32 s_gain[4], gw_gain[4];

- if (hist_r)
- ctrls->r_gain = div_u64(g_count, hist_r);
+ /*
+ * According to Grey World, we need to set gains for R/B to normalize
+ * them towards the green channel.
+ * Thus we want to keep Green as fixed and adjust only Red/Blue
+ * Compute the average of the both green channels first
+ */
+ avg = (u64)hist_count[ISC_HIS_CFG_MODE_GR] +
+ (u64)hist_count[ISC_HIS_CFG_MODE_GB];
+ avg >>= 1;
+
+ /* Green histogram is null, nothing to do */
+ if (!avg)
+ return;

- if (hist_b)
- ctrls->b_gain = div_u64(g_count, hist_b);
+ for (c = ISC_HIS_CFG_MODE_GR; c <= ISC_HIS_CFG_MODE_B; c++) {
+ /*
+ * the color offset is the minimum value of the histogram.
+ * we stretch this color to the full range by substracting
+ * this value from the color component.
+ */
+ offset[c] = ctrls->hist_minmax[c][HIST_MIN_INDEX];
+ /*
+ * The offset is always at least 1. If the offset is 1, we do
+ * not need to adjust it, so our result must be zero.
+ * the offset is computed in a histogram on 9 bits (0..512)
+ * but the offset in register is based on
+ * 12 bits pipeline (0..4096).
+ * we need to shift with the 3 bits that the histogram is
+ * ignoring
+ */
+ ctrls->offset[c] = (offset[c] - 1) << 3;
+
+ /* the offset is then taken and converted to 2's complements */
+ if (!ctrls->offset[c])
+ ctrls->offset[c] = ISC_WB_O_ZERO_VAL;
+
+ /*
+ * the stretch gain is the total number of histogram bins
+ * divided by the actual range of color component (Max - Min)
+ * If we compute gain like this, the actual color component
+ * will be stretched to the full histogram.
+ * We need to shift 9 bits for precision, we have 9 bits for
+ * decimals
+ */
+ s_gain[c] = (HIST_ENTRIES << 9) /
+ (ctrls->hist_minmax[c][HIST_MAX_INDEX] -
+ ctrls->hist_minmax[c][HIST_MIN_INDEX] + 1);
+
+ /*
+ * Now we have to compute the gain w.r.t. the average.
+ * Add/lose gain to the component towards the average.
+ * If it happens that the component is zero, use the
+ * fixed point value : 1.0 gain.
+ */
+ if (hist_count[c])
+ gw_gain[c] = div_u64(avg << 9, hist_count[c]);
+ else
+ gw_gain[c] = 1 << 9;
+
+ /* multiply both gains and adjust for decimals */
+ ctrls->gain[c] = s_gain[c] * gw_gain[c];
+ ctrls->gain[c] >>= 9;
+ }
}

static void isc_awb_work(struct work_struct *w)
@@ -1795,27 +1916,56 @@ static void isc_awb_work(struct work_struct *w)
struct isc_ctrls *ctrls = &isc->ctrls;
u32 hist_id = ctrls->hist_id;
u32 baysel;
+ unsigned long flags;
+ u32 min, max;
+
+ /* streaming is not active anymore */
+ if (isc->stop)
+ return;

if (ctrls->hist_stat != HIST_ENABLED)
return;

- isc_hist_count(isc);
+ isc_hist_count(isc, &min, &max);
+ ctrls->hist_minmax[hist_id][HIST_MIN_INDEX] = min;
+ ctrls->hist_minmax[hist_id][HIST_MAX_INDEX] = max;

if (hist_id != ISC_HIS_CFG_MODE_B) {
hist_id++;
} else {
isc_wb_update(ctrls);
- hist_id = ISC_HIS_CFG_MODE_R;
+ hist_id = ISC_HIS_CFG_MODE_GR;
}

ctrls->hist_id = hist_id;
baysel = isc->config.sd_format->cfa_baycfg << ISC_HIS_CFG_BAYSEL_SHIFT;

+ /* if no more auto white balance, reset controls. */
+ if (!ctrls->awb)
+ isc_reset_awb_ctrls(isc);
+
pm_runtime_get_sync(isc->dev);

+ /*
+ * only update if we have all the required histograms and controls
+ * if awb has been disabled, we need to reset registers as well.
+ */
+ if (hist_id == ISC_HIS_CFG_MODE_GR || !ctrls->awb) {
+ /*
+ * It may happen that DMA Done IRQ will trigger while we are
+ * updating white balance registers here.
+ * In that case, only parts of the controls have been updated.
+ * We can avoid that by locking the section.
+ */
+ spin_lock_irqsave(&isc->awb_lock, flags);
+ isc_update_awb_ctrls(isc);
+ spin_unlock_irqrestore(&isc->awb_lock, flags);
+ }
regmap_write(regmap, ISC_HIS_CFG, hist_id | baysel | ISC_HIS_CFG_RAR);
isc_update_profile(isc);
- regmap_write(regmap, ISC_CTRLEN, ISC_CTRL_HISREQ);
+ /* if awb has been disabled, we don't need to start another histogram */
+ if (ctrls->awb)
+ regmap_write(regmap, ISC_CTRLEN, ISC_CTRL_HISREQ);

pm_runtime_put_sync(isc->dev);
}
@@ -1839,8 +1989,7 @@ static int isc_s_ctrl(struct v4l2_ctrl *ctrl)
case V4L2_CID_AUTO_WHITE_BALANCE:
ctrls->awb = ctrl->val;
if (ctrls->hist_stat != HIST_ENABLED) {
- ctrls->r_gain = 0x1 << 9;
- ctrls->b_gain = 0x1 << 9;
+ isc_reset_awb_ctrls(isc);
}
break;
default:
@@ -1862,11 +2011,15 @@ static int isc_ctrl_init(struct isc_device *isc)
int ret;

ctrls->hist_stat = HIST_INIT;
+ isc_reset_awb_ctrls(isc);

ret = v4l2_ctrl_handler_init(hdl, 4);
if (ret < 0)
return ret;

+ ctrls->brightness = 0;
+ ctrls->contrast = 256;
+
v4l2_ctrl_new_std(hdl, ops, V4L2_CID_BRIGHTNESS, -1024, 1023, 1, 0);
v4l2_ctrl_new_std(hdl, ops, V4L2_CID_CONTRAST, -2048, 2047, 1, 256);
v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAMMA, 0, GAMMA_MAX, 1, 2);
@@ -2034,6 +2187,7 @@ static int isc_async_complete(struct v4l2_async_notifier *notifier)
/* Init video dma queues */
INIT_LIST_HEAD(&isc->dma_queue);
spin_lock_init(&isc->dma_queue_lock);
+ spin_lock_init(&isc->awb_lock);

ret = isc_formats_init(isc);
if (ret < 0) {
--
2.7.4
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