Re: [PATCH v5 09/12] media: microchip-isc: add SAMA7G5 hue and saturation controls

[Eugen Hristev <ehristev@kernel.org>]

On 5/27/26 14:07, Balakrishnan Sambath wrote:
> The CBHS (Contrast/Brightness/Hue/Saturation) block on SAMA7G5
> operates in YCbCr space; expose hue and saturation as V4L2 controls
> for the YUV/RGB output paths only. The SAMA5D2 has only the CBC
> block (no hue/saturation), so the controls are gated on a new
> has_cbhs flag.
> 
> Saturation uses the Q4 fixed-point range 0..127 with default 16
> (1.0x) directly matching the CBHS_SAT register field. The control
> state is initialised to neutral at probe so the first config_cbc()
> write after streaming starts does not produce a grayscale image.
> 
> Co-developed-by: Balamanikandan Gunasundar <balamanikandan.gunasundar@microchip.com>
> Signed-off-by: Balamanikandan Gunasundar <balamanikandan.gunasundar@microchip.com>
> Signed-off-by: Balakrishnan Sambath <balakrishnan.s@microchip.com>
> ---
>  .../media/platform/microchip/microchip-isc-base.c  | 75 ++++++++++++++++++++++
>  .../media/platform/microchip/microchip-isc-regs.h  | 11 ++--
>  drivers/media/platform/microchip/microchip-isc.h   |  3 +
>  .../platform/microchip/microchip-sama7g5-isc.c     |  6 +-
>  4 files changed, 88 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/platform/microchip/microchip-isc-base.c b/drivers/media/platform/microchip/microchip-isc-base.c
> index 04187127070d..cb338133d03f 100644
> --- a/drivers/media/platform/microchip/microchip-isc-base.c
> +++ b/drivers/media/platform/microchip/microchip-isc-base.c
> @@ -859,6 +859,56 @@ static int isc_try_configure_pipeline(struct isc_device *isc)
>  	return 0;
>  }
>  
> +static bool isc_format_has_chroma(u32 fourcc)
> +{
> +	switch (fourcc) {
> +	case V4L2_PIX_FMT_YUV420:
> +	case V4L2_PIX_FMT_YUV422P:
> +	case V4L2_PIX_FMT_YUYV:
> +	case V4L2_PIX_FMT_UYVY:
> +	case V4L2_PIX_FMT_VYUY:
> +		return true;
RGB565 doesn't have chroma for example ?

> +	default:
> +		return false;
> +	}
> +}
> +
> +/*
> + * isc_update_cbc_ctrl_activity() - Activate/deactivate CBC controls

What is the purpose of 'activity' in the name ? is a bit misleading for me.
> + *
> + * Called from isc_set_fmt(), isc_link_validate(), and isc_ctrl_init().
> + * At isc_ctrl_init() time isc->config.bits_pipeline is zero (no format
> + * has been negotiated yet), so all CBC controls are initially marked
> + * inactive.  They become active once a format that includes CBHS in the
> + * pipeline is configured via VIDIOC_S_FMT or link validation.
> + */
> +static void isc_update_cbc_ctrl_activity(struct isc_device *isc)
> +{
> +	struct v4l2_ctrl_handler *hdl = &isc->ctrls.handler;
> +	struct v4l2_ctrl *brightness;
> +	struct v4l2_ctrl *contrast;
> +	struct v4l2_ctrl *hue;
> +	struct v4l2_ctrl *saturation;
> +	bool cbc_active = isc->config.bits_pipeline & CBHS_ENABLE;
> +	bool chroma_active = cbc_active && isc_format_has_chroma(isc->config.fourcc);
> +
> +	brightness = v4l2_ctrl_find(hdl, V4L2_CID_BRIGHTNESS);
> +	if (brightness)
> +		v4l2_ctrl_activate(brightness, cbc_active);
> +
> +	contrast = v4l2_ctrl_find(hdl, V4L2_CID_CONTRAST);
> +	if (contrast)
> +		v4l2_ctrl_activate(contrast, cbc_active);
> +
> +	hue = v4l2_ctrl_find(hdl, V4L2_CID_HUE);
> +	if (hue)
> +		v4l2_ctrl_activate(hue, chroma_active);
> +
> +	saturation = v4l2_ctrl_find(hdl, V4L2_CID_SATURATION);
> +	if (saturation)
> +		v4l2_ctrl_activate(saturation, chroma_active);

Usage of v4l2_ctrl_find is a bit odd, don't you have the ctrls already
in the isc struct ? e.g. isc->ctrls.brightness, etc.

> +}
> +
>  static int isc_try_fmt(struct isc_device *isc, struct v4l2_format *f)
>  {
>  	struct v4l2_pix_format *pixfmt = &f->fmt.pix;
> @@ -902,6 +952,7 @@ static int isc_set_fmt(struct isc_device *isc, struct v4l2_format *f)
>  	/* make the try configuration active */
>  	isc->config = isc->try_config;
>  	isc->fmt = isc->try_fmt;
> +	isc_update_cbc_ctrl_activity(isc);
>  
>  	dev_dbg(isc->dev, "ISC set_fmt to %.4s @%dx%d\n",
>  		(char *)&f->fmt.pix.pixelformat,
> @@ -989,6 +1040,7 @@ static int isc_link_validate(struct media_link *link)
>  		return ret;
>  
>  	isc->config = isc->try_config;
> +	isc_update_cbc_ctrl_activity(isc);
>  
>  	dev_dbg(isc->dev, "New ISC configuration in place\n");
>  
> @@ -1457,6 +1509,14 @@ static int isc_s_ctrl(struct v4l2_ctrl *ctrl)
>  	case V4L2_CID_CONTRAST:
>  		ctrls->contrast = ctrl->val & ISC_CBC_CONTRAST_MASK;
>  		break;
> +	case V4L2_CID_HUE:
> +		if (isc->has_cbhs)
> +			ctrls->hue = ctrl->val & ISC_CBHS_HUE_MASK;
> +		break;
> +	case V4L2_CID_SATURATION:
> +		if (isc->has_cbhs)
> +			ctrls->saturation = ctrl->val & ISC_CBHS_SAT_MASK;
> +		break;
>  	case V4L2_CID_GAMMA:
>  		ctrls->gamma_index = ctrl->val;
>  		break;
> @@ -1464,6 +1524,7 @@ static int isc_s_ctrl(struct v4l2_ctrl *ctrl)
>  		return -EINVAL;
>  	}
>  
> +	/* config_cbc() flushes ctrls to hardware at stream start. */

What's the meaning of this comment here . s_ctrl configures multiple
controls, including gamma, etc, so why mention config_cbc() ?

>  	return 0;
>  }
>  
> @@ -1647,6 +1708,19 @@ static int isc_ctrl_init(struct isc_device *isc)
>  	ctrls->brightness = 0;
>  
>  	v4l2_ctrl_new_std(hdl, ops, V4L2_CID_BRIGHTNESS, -1024, 1023, 1, 0);
> +	if (isc->has_cbhs) {
> +		/*
> +		 * CBHS_HUE is a signed 9-bit value in degrees.
> +		 * CBHS_SAT is Q4 unsigned 7-bit, 16 = 1.0x.
> +		 * Initialize the kernel-side state to neutral here so the
> +		 * first config_cbc() call after streaming starts does not
> +		 * write zero (grayscale) to the hardware.
> +		 */
> +		ctrls->hue = 0;
> +		ctrls->saturation = 16;
> +		v4l2_ctrl_new_std(hdl, ops, V4L2_CID_HUE, -180, 180, 1, 0);
> +		v4l2_ctrl_new_std(hdl, ops, V4L2_CID_SATURATION, 0, 127, 1, 16);
> +	}
>  	v4l2_ctrl_new_std(hdl, ops, V4L2_CID_GAMMA, 0, isc->gamma_max, 1,
>  			  isc->gamma_default);
>  	isc->awb_ctrl = v4l2_ctrl_new_std(hdl, &isc_awb_ops,
> @@ -1665,6 +1739,7 @@ static int isc_ctrl_init(struct isc_device *isc)
>  	}
>  
>  	v4l2_ctrl_activate(isc->do_wb_ctrl, false);
> +	isc_update_cbc_ctrl_activity(isc);
>  
>  	isc->r_gain_ctrl = v4l2_ctrl_new_custom(hdl, &isc_r_gain_ctrl, NULL);
>  	isc->b_gain_ctrl = v4l2_ctrl_new_custom(hdl, &isc_b_gain_ctrl, NULL);
> diff --git a/drivers/media/platform/microchip/microchip-isc-regs.h b/drivers/media/platform/microchip/microchip-isc-regs.h
> index e77e1d9a1db8..7f5c2e50e74b 100644
> --- a/drivers/media/platform/microchip/microchip-isc-regs.h
> +++ b/drivers/media/platform/microchip/microchip-isc-regs.h
> @@ -268,10 +268,13 @@
>  #define ISC_CBC_CONTRAST	0x000003c0
>  #define ISC_CBC_CONTRAST_MASK	GENMASK(11, 0)
>  
> -/* Hue Register */
> -#define ISC_CBCHS_HUE	0x4e0
> -/* Saturation Register */
> -#define ISC_CBCHS_SAT	0x4e4
> +/* Hue Register: signed 9-bit two's complement, covers -180 to +180 degrees */
> +#define ISC_CBHS_HUE		0x4e0
> +#define ISC_CBHS_HUE_MASK	GENMASK(8, 0)
> +
> +/* Saturation Register: unsigned Q4 fixed-point (1.0 = 16, V4L2 range 0..127) */
> +#define ISC_CBHS_SAT		0x4e4
> +#define ISC_CBHS_SAT_MASK	GENMASK(6, 0)
>  
>  /* Offset for SUB422 register specific to sama5d2 product */
>  #define ISC_SAMA5D2_SUB422_OFFSET	0
> diff --git a/drivers/media/platform/microchip/microchip-isc.h b/drivers/media/platform/microchip/microchip-isc.h
> index 2282ef7dd596..36a9c0cb241f 100644
> --- a/drivers/media/platform/microchip/microchip-isc.h
> +++ b/drivers/media/platform/microchip/microchip-isc.h
> @@ -139,6 +139,8 @@ struct isc_ctrls {
>  
>  	u32 brightness;
>  	u32 contrast;
> +	u32 hue;
> +	u32 saturation;
>  	u8 gamma_index;
>  #define ISC_WB_NONE	0
>  #define ISC_WB_AUTO	1
> @@ -343,6 +345,7 @@ struct isc_device {
>  	const u32	(*gamma_table)[GAMMA_ENTRIES];
>  	u32		gamma_max;
>  	u32		gamma_default;
> +	bool		has_cbhs;
>  
>  	u32		max_width;
>  	u32		max_height;
> diff --git a/drivers/media/platform/microchip/microchip-sama7g5-isc.c b/drivers/media/platform/microchip/microchip-sama7g5-isc.c
> index 06aa801b88f9..f51c7cac25df 100644
> --- a/drivers/media/platform/microchip/microchip-sama7g5-isc.c
> +++ b/drivers/media/platform/microchip/microchip-sama7g5-isc.c
> @@ -257,9 +257,8 @@ static void isc_sama7g5_config_cbc(struct isc_device *isc)
>  	/* Configure what is set via v4l2 ctrls */
>  	regmap_write(regmap, ISC_CBC_BRIGHT + isc->offsets.cbc, isc->ctrls.brightness);
>  	regmap_write(regmap, ISC_CBC_CONTRAST + isc->offsets.cbc, isc->ctrls.contrast);
> -	/* Configure Hue and Saturation as neutral midpoint */
> -	regmap_write(regmap, ISC_CBCHS_HUE, 0);
> -	regmap_write(regmap, ISC_CBCHS_SAT, (1 << 4));
> +	regmap_write(regmap, ISC_CBHS_HUE, isc->ctrls.hue);
> +	regmap_write(regmap, ISC_CBHS_SAT, isc->ctrls.saturation);
>  }
>  
>  static void isc_sama7g5_config_cc(struct isc_device *isc)
> @@ -463,6 +462,7 @@ static int microchip_xisc_probe(struct platform_device *pdev)
>  	isc->gamma_max = 2;
>  	/* Index 1 in the SAMA7G5 table is gamma 1/2.2 (sRGB). */
>  	isc->gamma_default = 1;
> +	isc->has_cbhs = true;
>  
>  	if (of_machine_is_compatible("microchip,sam9x7")) {
>  		isc->max_width = ISC_SAM9X7_MAX_SUPPORT_WIDTH;
>