linux-kernel - Re: [PATCH v3 3/5] drm/panel: samsung-s6e88a0-ams427ap24: Add initial driver

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Message-ID: <CACRpkdY6w1LmKP+69TDRLJCszPpz_XAM_uoe8oC07MH-9ALAig@mail.gmail.com>
Date: Fri, 25 Oct 2024 18:36:59 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Jakob Hauser <jahau@...ketmail.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thierry Reding <thierry.reding@...il.com>, 
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v3 3/5] drm/panel: samsung-s6e88a0-ams427ap24: Add initial driver

Hi Jakob,

thanks for your patch!

On Thu, Oct 24, 2024 at 5:18 AM Jakob Hauser <jahau@...ketmail.com> wrote:

> This initial part of the panel driver was mostly generated by the
> "linux-mdss-dsi-panel-driver-generator" tool [1], reading downstream
> Android kernel file "dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi" [2].
>
> On top of the generic output of the tool, there were a couple of changes
> applied:
> - Added mipi_dsi_dcs_set_display_on() to function s6e88a0_ams427ap24_on(),
>   otherwise the display does not show up.
> - In functions s6e88a0_ams427ap24_on() and s6e88a0_ams427ap24_off()
>   changed DSI commands to multi context and used "accum_err" returns.
> - In functions s6e88a0_ams427ap24_on() and s6e88a0_ams427ap24_off() replaced
>   msleep() by mipi_dsi_msleep().
> - The function s6e88a0_ams427ap24_get_modes() was changed to make use of
>   drm_connector_helper_get_modes_fixed(). This also required to include
>   drm/drm_probe_helper.h.
> - In function s6e88a0_ams427ap24_probe() registring the regulators was changed
>   to devm_regulator_bulk_get_const(). This required to change supplies in struct
>   s6e88a0_ams427ap24 to a pointer.
> - Removed bool "prepared" from struct s6e88a0_ams427ap24 and according parts in
>   functions s6e88a0_ams427ap24_prepare() and s6e88a0_ams427ap24_unprepare().
>
> [1] https://github.com/msm8916-mainline/linux-mdss-dsi-panel-driver-generator
> [2] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi
>
> Signed-off-by: Jakob Hauser <jahau@...ketmail.com>

Nice job on this driver so far!

> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.h>

Why do you need this include? .of_match_table is part of
<linux/driver.h>

> +static int s6e88a0_ams427ap24_on(struct s6e88a0_ams427ap24 *ctx)
> +{
> +       struct mipi_dsi_device *dsi = ctx->dsi;
> +       struct mipi_dsi_multi_context dsi_ctx = { .dsi = dsi };
> +
> +       dsi->mode_flags |= MIPI_DSI_MODE_LPM;
> +
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0, 0x5a, 0x5a);

Can we provide #defines for at least some of this magic?
See other drivers for a very good idea of what some of them mean.
panel-samsung-s6d27a1.c:#define S6D27A1_PASSWD_L2       0xF0    /*
Password Command for Level 2 Control */
panel-samsung-s6d7aa0.c:#define MCS_PASSWD1             0xf0

> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfc, 0x5a, 0x5a);

panel-samsung-s6d7aa0.c:#define MCS_PASSWD3             0xfc

> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb0, 0x11);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfd, 0x11);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb0, 0x13);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfd, 0x18);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb0, 0x02);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb8, 0x30);
(...)
> +       mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
> +       mipi_dsi_msleep(&dsi_ctx, 20);
> +
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf1, 0x5a, 0x5a);

panel-samsung-s6d7aa0.c:#define MCS_PASSWD2             0xf1

> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcc, 0x4c);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf2, 0x03, 0x0d);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf1, 0xa5, 0xa5);

panel-samsung-s6d7aa0.c:#define MCS_PASSWD2             0xf1
Send in the reverse password: disable access.

> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xca,
> +                                    0x01, 0x00, 0x01, 0x00, 0x01, 0x00, 0x80,
> +                                    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
> +                                    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
> +                                    0x80, 0x80, 0x80, 0x80, 0x80, 0x80, 0x80,
> +                                    0x80, 0x80, 0x00, 0x00, 0x00);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb2,
> +                                    0x40, 0x08, 0x20, 0x00, 0x08);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb6, 0x28, 0x0b);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf7, 0x03);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0x55, 0x00);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0, 0xa5, 0xa5);
> +       mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfc, 0xa5, 0xa5);

Send in the reverse password: disable access.

A bit of #defines and comments would make it much more clear what
is going on.

Yours,
Linus Walleij