linux-kernel - Re: [PATCH 1/4] drm/panel/lpm102a188a: Switch to mipi_dsi_generic_write_seq

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Message-ID: <ecb7d7de-d674-49d2-b373-39041b363167@linaro.org>
Date: Wed, 29 Oct 2025 21:35:23 +0100
From: neil.armstrong@...aro.org
To: rtapadia730@...il.com, maarten.lankhorst@...ux.intel.com
Cc: mripard@...nel.org, tzimmermann@...e.de, airlied@...il.com,
 simona@...ll.ch, jessica.zhang@....qualcomm.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-doc@...r.kernel.org, corbet@....net
Subject: Re: [PATCH 1/4] drm/panel/lpm102a188a: Switch to
 mipi_dsi_generic_write_seq_multi()

On 9/21/25 20:37, rtapadia730@...il.com wrote:
> From: Rajeev Tapadia <rtapadia730@...il.com>
> 
> Replace deprecated mipi_dsi_generic_write_seq() calls with
> mipi_dsi_generic_write_seq_multi(). This avoids hidden early returns
> and matches the direction of other panel drivers.
> 
> No functional change intended.
> 
> Signed-off-by: Rajeev Tapadia <rtapadia730@...il.com>
> ---
> 
> Question for reviewers:
> In this patch, I switched to using mipi_dsi_generic_write_seq_multi().
> Currently, if both link1 and link2 return errors, only one error is
> reported via accum_err. How should this ideally be handled? Should we
> report the first error, the last, or combine them somehow?

No it's fine, the first error is catched and reported.

The good way to do this is via this macro:

#define mipi_dsi_dual_dcs_write_seq_multi(dsi_ctx, dsi0, dsi1, cmd, seq...)	\
		do {								\
			dsi_ctx.dsi = dsi0;					\
			mipi_dsi_dcs_write_seq_multi(&dsi_ctx, cmd, seq);	\
			dsi_ctx.dsi = dsi1;					\
			mipi_dsi_dcs_write_seq_multi(&dsi_ctx, cmd, seq);	\
		} while (0)

with a single context. The mipi_dsi_dcs_write_seq_multi will print the
error from the proper DSI and the context will have the appropriate error.

Neil

> 
>   drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c | 15 +++++++++++----
>   1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c b/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> index 5f897e143758..982cb61849a0 100644
> --- a/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> +++ b/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> @@ -162,27 +162,34 @@ static int jdi_setup_symmetrical_split(struct mipi_dsi_device *left,
>   static int jdi_write_dcdc_registers(struct jdi_panel *jdi)
>   {
>   	/* Clear the manufacturer command access protection */
> -	mipi_dsi_generic_write_seq(jdi->link1, MCS_CMD_ACS_PROT,
> +	struct mipi_dsi_multi_context dsi_ctx1 = {.dsi = jdi->link1};
> +	struct mipi_dsi_multi_context dsi_ctx2 = {.dsi = jdi->link2};
> +
> +	mipi_dsi_generic_write_seq_multi(&dsi_ctx1, MCS_CMD_ACS_PROT,
>   				   MCS_CMD_ACS_PROT_OFF);
> -	mipi_dsi_generic_write_seq(jdi->link2, MCS_CMD_ACS_PROT,
> +	mipi_dsi_generic_write_seq_multi(&dsi_ctx2, MCS_CMD_ACS_PROT,
>   				   MCS_CMD_ACS_PROT_OFF);
>   	/*
>   	 * Change the VGH/VGL divide rations to move the noise generated by the
>   	 * TCONN. This should hopefully avoid interaction with the backlight
>   	 * controller.
>   	 */
> -	mipi_dsi_generic_write_seq(jdi->link1, MCS_PWR_CTRL_FUNC,
> +	mipi_dsi_generic_write_seq_multi(&dsi_ctx1, MCS_PWR_CTRL_FUNC,
>   				   MCS_PWR_CTRL_PARAM1_VGH_330_DIV |
>   				   MCS_PWR_CTRL_PARAM1_DEFAULT,
>   				   MCS_PWR_CTRL_PARAM2_VGL_410_DIV |
>   				   MCS_PWR_CTRL_PARAM2_DEFAULT);
>   
> -	mipi_dsi_generic_write_seq(jdi->link2, MCS_PWR_CTRL_FUNC,
> +	mipi_dsi_generic_write_seq_multi(&dsi_ctx2, MCS_PWR_CTRL_FUNC,
>   				   MCS_PWR_CTRL_PARAM1_VGH_330_DIV |
>   				   MCS_PWR_CTRL_PARAM1_DEFAULT,
>   				   MCS_PWR_CTRL_PARAM2_VGL_410_DIV |
>   				   MCS_PWR_CTRL_PARAM2_DEFAULT);
>   
> +	if (dsi_ctx1.accum_err < 0)
> +		return dsi_ctx1.accum_err;
> +	if (dsi_ctx2.accum_err < 0)
> +		return dsi_ctx2.accum_err;
>   	return 0;
>   }
>