Re: [PATCH v2 1/3] drm/panel: jdi-lpm102a188a: Update deprecated MIPI function calls

Doug Anderson
2025-07-14T21:46:48Z

Hi,

On Tue, Jul 8, 2025 at 12:39 AM Brigham Campbell <me@brighamcampbell.com> wrote:
>
> Update jdi-lpm102a188a panel driver to use the "multi" variant of MIPI
> functions in order to facilitate improved error handling and remove the
> panel's dependency on deprecated MIPI functions.
>
> This patch's usage of the mipi_dsi_multi_context struct is not
> idiomatic. Rightfully, the struct wasn't designed to cater to the needs
> of panels with multiple MIPI DSI interfaces. This panel is an oddity
> which requires swapping the dsi pointer between MIPI function calls in
> order to preserve the exact behavior implemented using the non-multi
> variant of the macro.

Right. We dealt with this before with "novatek-nt36523"...

> Signed-off-by: Brigham Campbell <me@brighamcampbell.com>
> ---
> drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c | 160 +++++++-----------
> 1 file changed, 59 insertions(+), 101 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c b/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> index 5b5082efb282..5001bea1798f 100644
> --- a/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> +++ b/drivers/gpu/drm/panel/panel-jdi-lpm102a188a.c
> @@ -81,25 +81,20 @@ static int jdi_panel_disable(struct drm_panel *panel)
> static int jdi_panel_unprepare(struct drm_panel *panel)
> {
> struct jdi_panel *jdi = to_panel_jdi(panel);
> - int ret;
> + struct mipi_dsi_multi_context dsi_ctx;
>
> - ret = mipi_dsi_dcs_set_display_off(jdi->link1);
> - if (ret < 0)
> - dev_err(panel->dev, "failed to set display off: %d\n", ret);
> -
> - ret = mipi_dsi_dcs_set_display_off(jdi->link2);
> - if (ret < 0)
> - dev_err(panel->dev, "failed to set display off: %d\n", ret);
> + dsi_ctx.dsi = jdi->link1;
> + mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
> + dsi_ctx.dsi = jdi->link2;
> + mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
>
> /* Specified by JDI @ 50ms, subject to change */
> msleep(50);

Needs to be mipi_dsi_msleep() to avoid the sleep in case the above
commands caused an error.

> - ret = mipi_dsi_dcs_enter_sleep_mode(jdi->link1);
> - if (ret < 0)
> - dev_err(panel->dev, "failed to enter sleep mode: %d\n", ret);
> - ret = mipi_dsi_dcs_enter_sleep_mode(jdi->link2);
> - if (ret < 0)
> - dev_err(panel->dev, "failed to enter sleep mode: %d\n", ret);
> + dsi_ctx.dsi = jdi->link1;
> + mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
> + dsi_ctx.dsi = jdi->link2;
> + mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);

I think you need this here:

if (dsi_ctx.accum_err)
return dsi_ctx.accum_err;

...otherwise the code will do the sleeps, GPIO calls, and regulator
calls even in the case of an error. You don't want that. Then at the
end of the function you'd just have "return 0;"

> static int jdi_setup_symmetrical_split(struct mipi_dsi_device *left,
> struct mipi_dsi_device *right,
> const struct drm_display_mode *mode)
> {
> - int err;
> + struct mipi_dsi_multi_context dsi_ctx;

I think you should actually pass in the "dsi_ctx" to this function
since the caller already has one. Then you can change it to a "void"
function...

> static int jdi_write_dcdc_registers(struct jdi_panel *jdi)
> {

I think you want to pass the context into this function too and make
it "void". Then the caller doesn't need to check for the error before
calling it...

Then the "msleep(150)" after calling this function can change to a
`mipi_dsi_msleep()` and you don't need to check the error until right
before the LPM flag is cleared...

> + struct mipi_dsi_multi_context dsi_ctx;
> +
> /* Clear the manufacturer command access protection */
> - mipi_dsi_generic_write_seq(jdi->link1, MCS_CMD_ACS_PROT,
> + dsi_ctx.dsi = jdi->link1;
> + mipi_dsi_generic_write_seq_multi(&dsi_ctx, MCS_CMD_ACS_PROT,
> MCS_CMD_ACS_PROT_OFF);
> - mipi_dsi_generic_write_seq(jdi->link2, MCS_CMD_ACS_PROT,
> + dsi_ctx.dsi = jdi->link2;
> + mipi_dsi_generic_write_seq_multi(&dsi_ctx, MCS_CMD_ACS_PROT,
> MCS_CMD_ACS_PROT_OFF);

All the duplication is annoying. In "novatek-nt36523" I guess we only
needed to send _some_ of the commands to both panels and so we ended
up with a macro in just that C file just for
mipi_dsi_dual_dcs_write_seq_multi(). ...but here you seem to be
needing it for lots of functions.

Maybe the solution is to add something like this to "drm_mipi_dsi.h":

#define mipi_dsi_dual(_func, _dsi1, _dsi2, _ctx, _args...) \
do { \
(_ctx)->dsi = (_dsi1); \
(_func)((_ctx), _args); \
(_ctx)->dsi = (_dsi2); \
(_func)((_ctx), _args); \
} while (0)

Then you could have statements like:

mipi_dsi_dual(mipi_dsi_generic_write_seq_multi, jdi->link1,
jdi->link2, &dsi_ctx, ...);

I _think_ that will work? I at least prototyped it up with some simple
test code and it seemed to work... What do others think of that?

-Doug