Message-ID: <d852f997-aa40-390d-bca1-ec9bb330049d@ideasonboard.com>
Date:   Fri, 3 Feb 2023 17:12:51 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Aradhya Bhatia <a-bhatia1@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jyri Sarha <jyri.sarha@....fi>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     DRI Development List <dri-devel@...ts.freedesktop.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rahul T R <r-ravikumar@...com>,
        Devarsh Thakkar <devarsht@...com>,
        Jai Luthra <j-luthra@...com>,
        Jayesh Choudhary <j-choudhary@...com>
Subject: Re: [PATCH v7 4/6] drm/tidss: Add support to configure OLDI mode for
 am625-dss

On 25/01/2023 13:35, Aradhya Bhatia wrote:
> The newer version of DSS (AM625-DSS) has 2 OLDI TXes at its disposal.
> These can be configured to support the following modes:
> 
> 1. OLDI_SINGLE_LINK_SINGLE_MODE
> Single Output over OLDI 0.
> +------+        +---------+      +-------+
> |      |        |         |      |       |
> | CRTC +------->+ ENCODER +----->| PANEL |
> |      |        |         |      |       |
> +------+        +---------+      +-------+
> 
> 2. OLDI_SINGLE_LINK_CLONE_MODE
> Duplicate Output over OLDI 0 and 1.
> +------+        +---------+      +-------+
> |      |        |         |      |       |
> | CRTC +---+--->| ENCODER +----->| PANEL |
> |      |   |    |         |      |       |
> +------+   |    +---------+      +-------+
>             |
>             |    +---------+      +-------+
>             |    |         |      |       |
>             +--->| ENCODER +----->| PANEL |
>                  |         |      |       |
>                  +---------+      +-------+
> 
> 3. OLDI_DUAL_LINK_MODE
> Combined Output over OLDI 0 and 1.
> +------+        +---------+      +-------+
> |      |        |         +----->|       |
> | CRTC +------->+ ENCODER |      | PANEL |
> |      |        |         +----->|       |
> +------+        +---------+      +-------+
> 
> Following the above pathways for different modes, 2 encoder/panel-bridge
> pipes get created for clone mode, and 1 pipe in cases of single link and
> dual link mode.
> 
> Add support for confguring the OLDI modes using OF and LVDS DRM helper
> functions.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>   drivers/gpu/drm/tidss/tidss_dispc.c   |  24 ++-
>   drivers/gpu/drm/tidss/tidss_dispc.h   |  12 ++
>   drivers/gpu/drm/tidss/tidss_drv.h     |   3 +
>   drivers/gpu/drm/tidss/tidss_encoder.c |   4 +-
>   drivers/gpu/drm/tidss/tidss_encoder.h |   3 +-
>   drivers/gpu/drm/tidss/tidss_kms.c     | 221 ++++++++++++++++++++++++--
>   6 files changed, 245 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
> index b55ccbcaa67f..37a73e309330 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
> @@ -88,6 +88,8 @@ const struct dispc_features dispc_k2g_feats = {
>   
>   	.subrev = DISPC_K2G,
>   
> +	.has_oldi = false,
> +
>   	.common = "common",
>   
>   	.common_regs = tidss_k2g_common_regs,
> @@ -166,6 +168,8 @@ const struct dispc_features dispc_am625_feats = {
>   
>   	.subrev = DISPC_AM625,
>   
> +	.has_oldi = true,
> +
>   	.common = "common",
>   	.common_regs = tidss_am65x_common_regs,
>   
> @@ -218,6 +222,8 @@ const struct dispc_features dispc_am65x_feats = {
>   
>   	.subrev = DISPC_AM65X,
>   
> +	.has_oldi = true,
> +
>   	.common = "common",
>   	.common_regs = tidss_am65x_common_regs,
>   
> @@ -309,6 +315,8 @@ const struct dispc_features dispc_j721e_feats = {
>   
>   	.subrev = DISPC_J721E,
>   
> +	.has_oldi = false,
> +
>   	.common = "common_m",
>   	.common_regs = tidss_j721e_common_regs,
>   
> @@ -361,6 +369,8 @@ struct dispc_device {
>   
>   	struct dss_vp_data vp_data[TIDSS_MAX_VPS];
>   
> +	enum dispc_oldi_modes oldi_mode;
> +
>   	u32 *fourccs;
>   	u32 num_fourccs;
>   
> @@ -1963,6 +1973,12 @@ const u32 *dispc_plane_formats(struct dispc_device *dispc, unsigned int *len)
>   	return dispc->fourccs;
>   }
>   
> +void dispc_set_oldi_mode(struct dispc_device *dispc,
> +			 enum dispc_oldi_modes oldi_mode)
> +{
> +	dispc->oldi_mode = oldi_mode;
> +}
> +
>   static s32 pixinc(int pixels, u8 ps)
>   {
>   	if (pixels == 1)
> @@ -2647,7 +2663,7 @@ int dispc_runtime_resume(struct dispc_device *dispc)
>   		REG_GET(dispc, DSS_SYSSTATUS, 2, 2),
>   		REG_GET(dispc, DSS_SYSSTATUS, 3, 3));
>   
> -	if (dispc->feat->subrev == DISPC_AM65X)
> +	if (dispc->feat->has_oldi)
>   		dev_dbg(dispc->dev, "OLDI RESETDONE %d,%d,%d\n",
>   			REG_GET(dispc, DSS_SYSSTATUS, 5, 5),
>   			REG_GET(dispc, DSS_SYSSTATUS, 6, 6),
> @@ -2688,7 +2704,7 @@ static int dispc_iomap_resource(struct platform_device *pdev, const char *name,
>   	return 0;
>   }
>   
> -static int dispc_init_am65x_oldi_io_ctrl(struct device *dev,
> +static int dispc_init_am6xx_oldi_io_ctrl(struct device *dev,
>   					 struct dispc_device *dispc)
>   {
>   	dispc->oldi_io_ctrl =
> @@ -2827,8 +2843,8 @@ int dispc_init(struct tidss_device *tidss)
>   		dispc->vp_data[i].gamma_table = gamma_table;
>   	}
>   
> -	if (feat->subrev == DISPC_AM65X) {
> -		r = dispc_init_am65x_oldi_io_ctrl(dev, dispc);
> +	if (feat->has_oldi) {
> +		r = dispc_init_am6xx_oldi_io_ctrl(dev, dispc);
>   		if (r)
>   			return r;
>   	}
> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.h b/drivers/gpu/drm/tidss/tidss_dispc.h
> index 971f2856f015..880bc7de68b3 100644
> --- a/drivers/gpu/drm/tidss/tidss_dispc.h
> +++ b/drivers/gpu/drm/tidss/tidss_dispc.h
> @@ -64,6 +64,15 @@ enum dispc_dss_subrevision {
>   	DISPC_J721E,
>   };
>   
> +enum dispc_oldi_modes {
> +	OLDI_MODE_SINGLE_LINK,		/* Single output over OLDI 0. */
> +	OLDI_MODE_CLONE_SINGLE_LINK,	/* Cloned output over OLDI 0 and 1. */
> +	OLDI_MODE_DUAL_LINK,		/* Combined output over OLDI 0 and 1. */
> +	OLDI_MODE_OFF,			/* OLDI TXes not connected in OF. */
> +	OLDI_MODE_UNSUPPORTED,		/* Unsupported OLDI configuration in OF. */
> +	OLDI_MODE_UNAVAILABLE,		/* OLDI TXes not available in SoC. */
> +};
> +
>   struct dispc_features {
>   	int min_pclk_khz;
>   	int max_pclk_khz[DISPC_PORT_MAX_BUS_TYPE];
> @@ -72,6 +81,8 @@ struct dispc_features {
>   
>   	enum dispc_dss_subrevision subrev;
>   
> +	bool has_oldi;
> +
>   	const char *common;
>   	const u16 *common_regs;
>   	u32 num_vps;
> @@ -131,6 +142,7 @@ int dispc_plane_setup(struct dispc_device *dispc, u32 hw_plane,
>   		      u32 hw_videoport);
>   int dispc_plane_enable(struct dispc_device *dispc, u32 hw_plane, bool enable);
>   const u32 *dispc_plane_formats(struct dispc_device *dispc, unsigned int *len);
> +void dispc_set_oldi_mode(struct dispc_device *dispc, enum dispc_oldi_modes oldi_mode);
>   
>   int dispc_init(struct tidss_device *tidss);
>   void dispc_remove(struct tidss_device *tidss);
> diff --git a/drivers/gpu/drm/tidss/tidss_drv.h b/drivers/gpu/drm/tidss/tidss_drv.h
> index 0ce7ee5ccd5b..58892f065c16 100644
> --- a/drivers/gpu/drm/tidss/tidss_drv.h
> +++ b/drivers/gpu/drm/tidss/tidss_drv.h
> @@ -13,6 +13,9 @@
>   #define TIDSS_MAX_PLANES 4
>   #define TIDSS_MAX_OUTPUT_PORTS 4
>   
> +/* For AM625-DSS with 2 OLDI TXes */
> +#define TIDSS_MAX_BRIDGES_PER_PIPE	2
> +
>   typedef u32 dispc_irq_t;
>   
>   struct tidss_device {
> diff --git a/drivers/gpu/drm/tidss/tidss_encoder.c b/drivers/gpu/drm/tidss/tidss_encoder.c
> index 0d4865e9c03d..bd2a7358d7b0 100644
> --- a/drivers/gpu/drm/tidss/tidss_encoder.c
> +++ b/drivers/gpu/drm/tidss/tidss_encoder.c
> @@ -70,7 +70,8 @@ static const struct drm_encoder_funcs encoder_funcs = {
>   };
>   
>   struct drm_encoder *tidss_encoder_create(struct tidss_device *tidss,
> -					 u32 encoder_type, u32 possible_crtcs)
> +					 u32 encoder_type, u32 possible_crtcs,
> +					 u32 possible_clones)
>   {
>   	struct drm_encoder *enc;
>   	int ret;
> @@ -80,6 +81,7 @@ struct drm_encoder *tidss_encoder_create(struct tidss_device *tidss,
>   		return ERR_PTR(-ENOMEM);
>   
>   	enc->possible_crtcs = possible_crtcs;
> +	enc->possible_clones = possible_clones;
>   
>   	ret = drm_encoder_init(&tidss->ddev, enc, &encoder_funcs,
>   			       encoder_type, NULL);
> diff --git a/drivers/gpu/drm/tidss/tidss_encoder.h b/drivers/gpu/drm/tidss/tidss_encoder.h
> index ace877c0e0fd..01c62ba3ef16 100644
> --- a/drivers/gpu/drm/tidss/tidss_encoder.h
> +++ b/drivers/gpu/drm/tidss/tidss_encoder.h
> @@ -12,6 +12,7 @@
>   struct tidss_device;
>   
>   struct drm_encoder *tidss_encoder_create(struct tidss_device *tidss,
> -					 u32 encoder_type, u32 possible_crtcs);
> +					 u32 encoder_type, u32 possible_crtcs,
> +					 u32 possible_clones);
>   
>   #endif
> diff --git a/drivers/gpu/drm/tidss/tidss_kms.c b/drivers/gpu/drm/tidss/tidss_kms.c
> index d449131935d2..8322ee6310bf 100644
> --- a/drivers/gpu/drm/tidss/tidss_kms.c
> +++ b/drivers/gpu/drm/tidss/tidss_kms.c
> @@ -13,6 +13,7 @@
>   #include <drm/drm_of.h>
>   #include <drm/drm_panel.h>
>   #include <drm/drm_vblank.h>
> +#include <linux/of.h>
>   
>   #include "tidss_crtc.h"
>   #include "tidss_dispc.h"
> @@ -104,26 +105,129 @@ static const struct drm_mode_config_funcs mode_config_funcs = {
>   	.atomic_commit = drm_atomic_helper_commit,
>   };
>   
> +static enum dispc_oldi_modes tidss_get_oldi_mode(struct tidss_device *tidss)
> +{
> +	int pixel_order;
> +	enum dispc_oldi_modes oldi_mode;
> +	struct device_node *oldi0_port, *oldi1_port;
> +
> +	/*
> +	 * For am625-dss, the OLDI ports are expected at port reg = 0 and 2,
> +	 * and for am65x-dss, the OLDI port is expected only at port reg = 0.
> +	 */
> +	const u32 portnum_oldi0 = 0, portnum_oldi1 = 2;
> +
> +	oldi0_port = of_graph_get_port_by_id(tidss->dev->of_node, portnum_oldi0);
> +	oldi1_port = of_graph_get_port_by_id(tidss->dev->of_node, portnum_oldi1);
> +
> +	if (!(oldi0_port || oldi1_port)) {
> +		/* Keep OLDI TXes OFF if neither OLDI port is present. */
> +		oldi_mode = OLDI_MODE_OFF;
> +	} else if (oldi0_port && !oldi1_port) {
> +		/*
> +		 * OLDI0 port found, but not OLDI1 port. Setting single
> +		 * link output mode.
> +		 */
> +		oldi_mode = OLDI_MODE_SINGLE_LINK;
> +	} else if (!oldi0_port && oldi1_port) {
> +		/*
> +		 * The 2nd OLDI TX cannot be operated alone. This use case is
> +		 * not supported in the HW. Since the pins for OLDIs 0 and 1 are
> +		 * separate, one could theoretically set a clone mode over OLDIs
> +		 * 0 and 1 and just simply not use the OLDI 0. This is a hacky
> +		 * way to enable only OLDI TX 1 and hence is not officially
> +		 * supported.
> +		 */
> +		dev_warn(tidss->dev,
> +			 "Single Mode over OLDI 1 is not supported in HW.\n");
> +		oldi_mode = OLDI_MODE_UNSUPPORTED;
> +	} else {
> +		/*
> +		 * OLDI Ports found for both the OLDI TXes. The DSS is to be
> +		 * configured in either Dual Link or Clone Mode.
> +		 */
> +		pixel_order = drm_of_lvds_get_dual_link_pixel_order(oldi0_port,
> +								    oldi1_port);
> +		switch (pixel_order) {
> +		case -EINVAL:
> +			/*
> +			 * The dual link properties were not found in at least
> +			 * one of the sink nodes. Since 2 OLDI ports are present
> +			 * in the DT, it can be safely assumed that the required
> +			 * configuration is Clone Mode.
> +			 */
> +			oldi_mode = OLDI_MODE_CLONE_SINGLE_LINK;
> +			break;
> +
> +		case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
> +			/*
> +			 * Note that the OLDI TX 0 transmits the odd set of
> +			 * pixels while the OLDI TX 1 transmits the even set.
> +			 * This is a fixed configuration in the HW and an cannot
> +			 * be change via SW.
> +			 */
> +			dev_warn(tidss->dev,
> +				 "EVEN-ODD Dual-Link Mode is not supported in HW.\n");
> +			oldi_mode = OLDI_MODE_UNSUPPORTED;
> +			break;
> +
> +		case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
> +			oldi_mode = OLDI_MODE_DUAL_LINK;
> +			break;
> +
> +		default:
> +			oldi_mode = OLDI_MODE_UNSUPPORTED;
> +			break;
> +		}
> +	}
> +
> +	of_node_put(oldi0_port);
> +	of_node_put(oldi1_port);
> +
> +	return oldi_mode;
> +}
> +
>   static int tidss_dispc_modeset_init(struct tidss_device *tidss)
>   {
>   	struct device *dev = tidss->dev;
>   	unsigned int fourccs_len;
>   	const u32 *fourccs = dispc_plane_formats(tidss->dispc, &fourccs_len);
> -	unsigned int i;
> +	unsigned int i, j;
>   
>   	struct pipe {
>   		u32 hw_videoport;
> -		struct drm_bridge *bridge;
> +		struct drm_bridge *bridge[TIDSS_MAX_BRIDGES_PER_PIPE];
>   		u32 enc_type;
> +		u32 num_bridges;
>   	};
>   
>   	const struct dispc_features *feat = tidss->feat;
>   	u32 output_ports = feat->num_output_ports;
>   	u32 max_planes = feat->num_planes;
>   
> -	struct pipe pipes[TIDSS_MAX_VPS];
> +	struct pipe pipes[TIDSS_MAX_VPS] = {0};
> +
>   	u32 num_pipes = 0;
>   	u32 crtc_mask;
> +	enum dispc_oldi_modes oldi_mode = OLDI_MODE_UNAVAILABLE;
> +	u32 num_oldi = 0;
> +	u32 num_encoders = 0;
> +	u32 oldi_pipe_index = 0;
> +
> +	if (feat->has_oldi) {
> +		oldi_mode = tidss_get_oldi_mode(tidss);
> +
> +		if ((oldi_mode == OLDI_MODE_DUAL_LINK ||
> +		     oldi_mode == OLDI_MODE_CLONE_SINGLE_LINK) &&
> +		    feat->subrev == DISPC_AM65X) {
> +			dev_warn(tidss->dev,
> +				 "am65x-dss does not support this OLDI mode.\n");
> +
> +			oldi_mode = OLDI_MODE_UNSUPPORTED;
> +		}

Shouldn't OLDI_MODE_UNSUPPORTED be handled as an error? It means the DT 
is faulty, doesn't it? Maybe it could even be renamed to 
OLDI_MODE_ERROR. Or tidss_get_oldi_mode() could return a negative error 
code.

> +
> +		dispc_set_oldi_mode(tidss->dispc, oldi_mode);
> +	}

Would it be better to move the above dispc_set_oldi_mode() to be outside 
the if block? Then oldi mode would be set to OLDI_MODE_UNAVAILABLE on 
SoCs that don't have OLDI.

tidss_get_oldi_mode and dispc_set_oldi_mode sound like opposites, but 
they're totally different things. Maybe tidss_get_oldi_mode should 
rather be something about parsing oldi dt properties or such.

>   	/* first find all the connected panels & bridges */
>   
> @@ -179,10 +283,87 @@ static int tidss_dispc_modeset_init(struct tidss_device *tidss)
>   			}
>   		}
>   
> -		pipes[num_pipes].hw_videoport = i;
> -		pipes[num_pipes].bridge = bridge;
> -		pipes[num_pipes].enc_type = enc_type;
> -		num_pipes++;
> +		if (feat->output_port_bus_type[i] == DISPC_PORT_OLDI) {
> +			switch (oldi_mode) {
> +			case OLDI_MODE_UNSUPPORTED:
> +			case OLDI_MODE_OFF:
> +				/*
> +				 * Either the OLDI ports are not connected in
> +				 * OF, or their configuration mode is not
> +				 * supported.
> +				 * In both the cases, the OLDI sink ports shall
> +				 * not be logically connected to DSS ports.
> +				 *
> +				 * However, since other dss ports might still
> +				 * be in use (eg, for DPI), the driver shall
> +				 * continue to find the next connected sink in
> +				 * OF.
> +				 */
> +				dev_dbg(dev, "OLDI disconnected on port %d\n", i);
> +				continue;
> +
> +			case OLDI_MODE_DUAL_LINK:
> +				/*
> +				 * The 2nd OLDI port of a dual-link sink does
> +				 * not require a separate bridge entity.
> +				 */
> +				if (num_oldi) {

I think if (num_oldi > 0) makes it more readable.

> +					drm_panel_bridge_remove(bridge);
> +					continue;
> +				}
> +
> +				fallthrough;
> +
> +			case OLDI_MODE_CLONE_SINGLE_LINK:
> +			case OLDI_MODE_SINGLE_LINK:
> +				/*
> +				 * Setting up pipe parameters when 1st OLDI
> +				 * port is detected.
> +				 */
> +				if (!num_oldi) {

And here if (num_oldi == 0).

> +					pipes[num_pipes].hw_videoport = i;
> +					pipes[num_pipes].enc_type = enc_type;
> +
> +					/*
> +					 * Saving the pipe index in case its
> +					 * required for 2nd OLDI Port.
> +					 */
> +					oldi_pipe_index = num_pipes;
> +
> +					/*
> +					 * Incrememnt num_pipe when 1st oldi
> +					 * port is discovered. For the 2nd OLDI
> +					 * port, num_pipe need not be
> +					 * incremented because the 2nd
> +					 * Encoder-to-Bridge connection will
> +					 * still be the part of the first OLDI
> +					 * Port pipe.
> +					 */
> +					num_pipes++;
> +				}
> +
> +				/*
> +				 * Bridge is required to be added only if the
> +				 * detected port is the first OLDI port (of any
> +				 * mode) or a subsequent port in Clone Mode.
> +				 */

If I understand right, you're saying that bridge is not required to be 
added for the second port for dual link? It maybe be clearer to state 
that. But if so, isn't this still always adding the bridge here, for all 
modes? Or what is the comment referring to?

  Tomi

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