linux-kernel - Re: [PATCH v5 1/5] drm/panel: jd9365da: Modify the method of sending commands

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Date: Fri, 28 Jun 2024 10:32:02 +0200
From: neil.armstrong@...aro.org
To: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>,
 dmitry.torokhov@...il.com, robh@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, jikos@...nel.org,
 benjamin.tissoires@...hat.co, dianders@...gle.com, hsinyi@...gle.com,
 jagan@...eble.ai, quic_jesszhan@...cinc.com, dmitry.baryshkov@...aro.org
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] drm/panel: jd9365da: Modify the method of sending
 commands

On 24/06/2024 16:19, Zhaoxiong Lv wrote:
> Currently, the init_code of the jd9365da driver is placed
> in the enable() function and sent, but this seems to take
> a long time. It takes 17ms to send each instruction (an init
> code consists of about 200 instructions), so it takes
> about 3.5s to send the init_code. So we moved the sending
> of the inti_code to the prepare() function, and each
> instruction seemed to take only 25μs.
> 
> We checked the DSI host and found that the difference in
> command sending time is caused by the different modes of
> the DSI host in prepare() and enable() functions.
> Our DSI Host only supports sending cmd in LP mode, The
> prepare() function can directly send init_code (LP->cmd)
> in LP mode, but the enable() function is in HS mode and
> needs to switch to LP mode before sending init code
> (HS->LP->cmd->HS). Therefore, it takes longer to send
> the command.
> 
> Signed-off-by: Zhaoxiong Lv <lvzhaoxiong@...qin.corp-partner.google.com>
> ---
> Changes between V5 and V4:
> - 1. No changes.
> 
> V4:https://lore.kernel.org/all/20240620080509.18504-2-lvzhaoxiong@huaqin.corp-partner.google.com/
> 
> Changes between V4 and V3:
> - 1. Only move mipi_dsi_dcs_write_buffer from enable() function to prepare() function,
> -    and no longer use mipi_dsi_dcs_write_seq_multi.
> 
> V3:https://lore.kernel.org/all/20240614145510.22965-2-lvzhaoxiong@huaqin.corp-partner.google.com/
> 
> ---
>   .../gpu/drm/panel/panel-jadard-jd9365da-h3.c  | 24 +++++++++----------
>   1 file changed, 11 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> index 4879835fe101..a9c483a7b3fa 100644
> --- a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> +++ b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> @@ -52,21 +52,9 @@ static int jadard_enable(struct drm_panel *panel)
>   {
>   	struct device *dev = panel->dev;
>   	struct jadard *jadard = panel_to_jadard(panel);
> -	const struct jadard_panel_desc *desc = jadard->desc;
>   	struct mipi_dsi_device *dsi = jadard->dsi;
> -	unsigned int i;
>   	int err;
>   
> -	msleep(10);
> -
> -	for (i = 0; i < desc->num_init_cmds; i++) {
> -		const struct jadard_init_cmd *cmd = &desc->init_cmds[i];
> -
> -		err = mipi_dsi_dcs_write_buffer(dsi, cmd->data, JD9365DA_INIT_CMD_LEN);
> -		if (err < 0)
> -			return err;
> -	}
> -
>   	msleep(120);
>   
>   	err = mipi_dsi_dcs_exit_sleep_mode(dsi);
> @@ -100,6 +88,8 @@ static int jadard_disable(struct drm_panel *panel)
>   static int jadard_prepare(struct drm_panel *panel)
>   {
>   	struct jadard *jadard = panel_to_jadard(panel);
> +	const struct jadard_panel_desc *desc = jadard->desc;
> +	unsigned int i;
>   	int ret;
>   
>   	ret = regulator_enable(jadard->vccio);
> @@ -117,7 +107,15 @@ static int jadard_prepare(struct drm_panel *panel)
>   	msleep(10);
>   
>   	gpiod_set_value(jadard->reset, 1);
> -	msleep(120);
> +	msleep(130);
> +
> +	for (i = 0; i < desc->num_init_cmds; i++) {
> +		const struct jadard_init_cmd *cmd = &desc->init_cmds[i];
> +
> +		ret = mipi_dsi_dcs_write_buffer(dsi, cmd->data, JD9365DA_INIT_CMD_LEN);
> +		if (ret < 0)
> +			return ret;
> +	}
>   
>   	return 0;
>   }

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>