Message-ID: <CAGWqDJ4ESRxNe59+q2KaEK5YO-X5od_CbyKn7V5dJh0PJZJHtg@mail.gmail.com>
Date:	Wed, 15 Jun 2016 18:41:11 +0530
From:	Vinay Simha <simhavcs@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Archit Taneja <archit.taneja@...il.com>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	John Stultz <john.stultz@...aro.org>,
	Rob Clark <robdclark@...il.com>,
	David Airlie <airlied@...ux.ie>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:DRM PANEL DRIVERS" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v4 2/2] drm/panel: Add JDI LT070ME05000 WUXGA DSI Panel

On Mon, Jun 13, 2016 at 6:05 PM, Thierry Reding
<thierry.reding@...il.com> wrote:
> On Mon, Jun 13, 2016 at 03:55:28PM +0530, Vinay Simha BN wrote:
>> Add support for the JDI lt070me05000 WUXGA DSI panel used in
>
> Can you please make the names consistent? Use the all-uppercase spelling
> for the panel model.
>
>> Nexus 7 2013 devices.
>>
>> Programming sequence for the panel is was originally found in the
>> android-msm-flo-3.4-lollipop-release branch from:
>>     https://android.googlesource.com/kernel/msm.git
>>
>> And video mode setting is from dsi-panel-jdi-dualmipi1-video.dtsi
>> file in:
>>     git://codeaurora.org/kernel/msm-3.10.git  LNX.LA.3.6_rb1.27
>>
>> Cc: Archit Taneja <archit.taneja@...il.com>
>> [sumit.semwal: Ported to the drm/panel framework]
>> Signed-off-by: Sumit Semwal <sumit.semwal@...aro.org>
>> [jstultz: Cherry-picked to mainline, folded down other fixes
>>  from Vinay and Archit]
>> Signed-off-by: John Stultz <john.stultz@...aro.org>
>> [vinay simha bn: removed interface setting cmd mode, video
>> mode panel setting selection]
>> Cc: Rob Clark <robdclark@...il.com>
>> Signed-off-by: Vinay Simha BN <simhavcs@...il.com>
>> --
>> v2:
>>  * incorporated code reviews from theiry, archit
>>    code style, alphabetical soring in Makefile, Kconfig, regulator_bulk,
>>    arrays of u8, generic helper function, documentation bindings,
>>
>> v3:
>>  * dcs backlight support added
>>  * tested this panel driver in nexus7 2013 device
>>
>> v4:
>>  * backlight interface added in the panel driver
>>  * incorporated width_mm and height_mm suggested by rob herring
>> ---
>>  drivers/gpu/drm/panel/Kconfig                  |  11 +
>>  drivers/gpu/drm/panel/Makefile                 |   1 +
>>  drivers/gpu/drm/panel/panel-jdi-lt070me05000.c | 539 +++++++++++++++++++++++++
>>  3 files changed, 551 insertions(+)
>>  create mode 100644 drivers/gpu/drm/panel/panel-jdi-lt070me05000.c
>>
>> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
>> index 1500ab9..83e89e7 100644
>> --- a/drivers/gpu/drm/panel/Kconfig
>> +++ b/drivers/gpu/drm/panel/Kconfig
>> @@ -7,6 +7,17 @@ config DRM_PANEL
>>  menu "Display Panels"
>>       depends on DRM && DRM_PANEL
>>
>> +config DRM_PANEL_JDI_LT070ME05000
>> +        tristate "JDI LT070ME05000 WUXGA DSI panel"
>> +        depends on OF
>> +        depends on DRM_MIPI_DSI
>> +        depends on BACKLIGHT_CLASS_DEVICE
>> +        help
>
> Please use consistent indentation here. Also, this is badly sorted. The
> DRM_PANEL_SIMPLE is special in that it doesn't have a vendor prefix, all
> others should be sorted after panel-simple and in alphabetical order by
> vendor, then model.
>
>> +        Say Y here if you want to enable support for JDI WUXGA DSI video
>> +        mode panel as found in Google Nexus 7 (2013) devices.
>> +        The panel has a 1200(RGB)×1920 (WUXGA) resolution and uses
>> +        24 bit RGB per pixel.
>
> It's kind of redundant to say 1200(RGB) when you say that it's 24 bit
> RGB afterwards. You also repeat WUXGA twice, so you can drop either of
> the occurrences as well.
>
>> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
>> index f277eed..5d74ac2 100644
>> --- a/drivers/gpu/drm/panel/Makefile
>> +++ b/drivers/gpu/drm/panel/Makefile
>> @@ -1,3 +1,4 @@
>> +obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
>
> Please sort this the same way as the Kconfig entries.
>
>>  obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
>>  obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
>>  obj-$(CONFIG_DRM_PANEL_PANASONIC_VVX10F034N00) += panel-panasonic-vvx10f034n00.o
>> diff --git a/drivers/gpu/drm/panel/panel-jdi-lt070me05000.c b/drivers/gpu/drm/panel/panel-jdi-lt070me05000.c
>> new file mode 100644
>> index 0000000..8657e5f
>> --- /dev/null
>> +++ b/drivers/gpu/drm/panel/panel-jdi-lt070me05000.c
>> @@ -0,0 +1,539 @@
>> +/*
>> + * Copyright (C) 2016 InforceComputing
>> + * Author: Vinay Simha BN <simhavcs@...il.com>
>> + *
>> + * Copyright (C) 2016 Linaro Ltd
>> + * Author: Sumit Semwal <sumit.semwal@...aro.org>
>> + *
>> + * From internet archives, the panel for Nexus 7 2nd Gen, 2013 model is a
>> + * JDI model LT070ME05000, and its data sheet is at:
>> + * http://panelone.net/en/7-0-inch/JDI_LT070ME05000_7.0_inch-datasheet
>> + *
>> + * This program is free software; you can redistribute it and/or modify it
>> + * under the terms of the GNU General Public License version 2 as published by
>> + * the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful, but WITHOUT
>> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
>> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
>> + * more details.
>> + *
>> + * You should have received a copy of the GNU General Public License along with
>> + * this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +#include <linux/backlight.h>
>> +#include <linux/gpio/consumer.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/regulator/consumer.h>
>> +
>> +#include <drm/drmP.h>
>> +#include <drm/drm_crtc.h>
>> +#include <drm/drm_mipi_dsi.h>
>> +#include <drm/drm_panel.h>
>> +
>> +#include <video/mipi_display.h>
>> +
>> +#define PANEL_DEV_REGULATOR_MAX   3
>
> _MAX suggests that the number of regulators is actually variable, but
> it's not. PANEL_NUM_REGULATORS, perhaps?
>
>> +#define PANEL_MAX_BRIGHTNESS 0xFF
>
> There isn't really a need for this macro, you only use the constant in
> one location. Also, a brightness is usually represented in decimal.
>
>> +const char *regs[] = {
>> +     "vddp",
>> +     "dcdc_en",
>> +     "vcc"
>> +};
>
> This should be static. Also use a more sensible name, such as
> regulator_names, please.
>
>> +static int jdi_panel_init(struct jdi_panel *jdi)
>> +{
> [...]
>> +     struct mipi_dsi_device *dsi = jdi->dsi;
>> +     int ret;
>> +
>> +     dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +     ret = mipi_dsi_dcs_soft_reset(dsi);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     usleep_range(10000, 20000);
>> +
>> +     ret = mipi_dsi_dcs_set_pixel_format(dsi, 0x70);
>> +     if (ret < 0)
>> +             return ret;
>
> Please use the existing symbolic constants for this.
>
>> +
>> +     ret = mipi_dsi_dcs_set_column_address(dsi, 0x0000, 0x04AF);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     ret = mipi_dsi_dcs_set_page_address(dsi, 0x0000, 0x077F);
>> +     if (ret < 0)
>> +             return ret;
>
> Please parameterize these using the panel width and height.
>
>> +
>> +     ret = mipi_dsi_dcs_set_tear_on(dsi,
>> +                                    MIPI_DSI_DCS_TEAR_MODE_VBLANK);
>> +     if (ret < 0)
>> +             return ret;
>> +     usleep_range(5000, 10000);
>
> Use a blank line after conditional blocks, please.
>
>> +
>> +     ret = mipi_dsi_set_tear_scanline(dsi, 0x0300);
>> +     if (ret < 0)
>> +             return ret;
>
> Might be worth making this a decimal. But then the question begs: why is
> 768 a good value for the tear scanline? Also, should you not set the
> tear scanline before enabling tear mode?
>
>> +
>> +     ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_SET_DISPLAY_BRIGHTNESS,
>> +                              (u8[]){ 0xFF }, 1);
>> +     if (ret < 0)
>> +             return ret;
>
> Is this necessary? Shouldn't the backlight implementation set this upon
> registration already?
>
>> +
>> +     ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_WRITE_CONTROL_DISPLAY,
>> +                              (u8[]){ 0x24 }, 1);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     ret = mipi_dsi_dcs_write(dsi, MIPI_DCS_WRITE_POWER_SAVE,
>> +                              (u8[]){ 0x00 }, 1);
>> +     if (ret < 0)
>> +             return ret;
>
> What do these mean?
>
>> +
>> +     ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
>> +     if (ret < 0)
>> +             return ret;
>> +     mdelay(120);
>
> Again, could use an extra blank line for readability. Also, don't ever
> use mdelay() for such large delays! Use msleep() instead.
>
>> +     ret = mipi_dsi_generic_write(dsi, (u8[]){0xB0, 0x00}, 2);
>> +     if (ret < 0)
>> +             return ret;
>> +     mdelay(10);
>
> Same here. This also needs at least a comment, though ideally you'd use
> symbolic names for those magic numbers.
>
>> +     ret = mipi_dsi_generic_write(dsi, (u8[])
>> +                                  {0xB3, 0x26, 0x08, 0x00, 0x20, 0x00}, 6);
>> +     if (ret < 0)
>> +             return ret;
>> +     mdelay(20);
>
> And here.
>
>> +static int jdi_panel_unprepare(struct drm_panel *panel)
>> +{
>> +     struct jdi_panel *jdi = to_jdi_panel(panel);
>> +     struct regulator_bulk_data *s = jdi->supplies;
>> +     int num = PANEL_DEV_REGULATOR_MAX;
>> +     struct device *dev = &jdi->dsi->dev;
>> +     int ret;
>> +
>> +     if (!jdi->prepared)
>> +             return 0;
>> +
>> +     DRM_DEBUG("unprepare\n");
>> +
>> +     ret = jdi_panel_off(jdi);
>> +     if (ret) {
>> +             dev_err(panel->dev, "failed to set panel off: %d\n", ret);
>> +             return ret;
>> +     }
>> +
>> +     ret = regulator_bulk_disable(num, s);
>> +     if (ret < 0) {
>> +             dev_err(dev, "regulator disable failed, %d\n", ret);
>> +             return ret;
>> +     }
>> +
>> +     if (jdi->reset_gpio)
>> +             gpiod_set_value(jdi->reset_gpio, 0);
>
> That's odd. Wouldn't you typically assert the reset in ->unprepare()?
> Perhaps you need to mark the GPIO as GPIO_ACTIVE_LOW?
in prepare() reset_gpio and enable_gpio are active high
   unprepare() reset_gpio and enable_gpio are active low
do i am missing any flag settings?
>
>> +     if (jdi->enable_gpio)
>> +             gpiod_set_value(jdi->enable_gpio, 0);
>> +
>> +     jdi->prepared = false;
>> +
>> +     return 0;
>> +}
>> +
>> +static int jdi_panel_prepare(struct drm_panel *panel)
>> +{
>> +     struct jdi_panel *jdi = to_jdi_panel(panel);
>> +     struct regulator_bulk_data *s = jdi->supplies;
>
> There's no need for this temporary variable, jdi->supplies isn't
> terrible long.
>
>> +     int num = PANEL_DEV_REGULATOR_MAX;
>
> This should be unsigned int. Also, might be worth to simply drop this
> usage and do...
>
>> +     struct device *dev = &jdi->dsi->dev;
>> +     int ret;
>> +
>> +     if (jdi->prepared)
>> +             return 0;
>> +
>> +     DRM_DEBUG("prepare\n");
>> +
>> +     ret = regulator_bulk_enable(num, s);
>
>         ret = regulator_bulk_enable(ARRAY_SIZE(jdi->supplies), jdi->supplies);
>
> here.
>
>> +     if (ret < 0) {
>> +             dev_err(dev, "regulator enable failed, %d\n", ret);
>
> Can you please be more consistent with how you report errors? Other
> drivers use "...: %d\n", ret and you do so yourself in other parts of
> this same driver, so make them all consistent, please.
>
>> +static int jdi_panel_enable(struct drm_panel *panel)
>> +{
>> +     struct jdi_panel *jdi = to_jdi_panel(panel);
>> +
>> +     if (jdi->enabled)
>> +             return 0;
>> +
>> +     DRM_DEBUG("enable\n");
>
> Do you really need these? You can use the kernel's built-in function
> tracing for the same purpose.
>
>> +static const struct drm_display_mode default_mode = {
>> +             .clock = 155493,
>> +             .hdisplay = 1200,
>> +             .hsync_start = 1200 + 48,
>> +             .hsync_end = 1200 + 48 + 32,
>> +             .htotal = 1200 + 48 + 32 + 60,
>> +             .vdisplay = 1920,
>> +             .vsync_start = 1920 + 3,
>> +             .vsync_end = 1920 + 3 + 5,
>> +             .vtotal = 1920 + 3 + 5 + 6,
>> +             .vrefresh = 60,
>> +             .flags = 0,
>> +             .width_mm = 95,
>> +             .height_mm = 151,
>
> It's slightly unusual to set this in the mode. Typically you'd set the
> connector->display_info.{width,height}_mm directly.
>
>> +static int dsi_dcs_bl_get_brightness(struct backlight_device *bl)
>> +{
>> +     struct mipi_dsi_device *dsi = bl_get_data(bl);
>> +     int ret;
>> +     u16 brightness;
>> +     u8 bl_value[2];
>> +
>> +     dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
>> +
>> +     ret = mipi_dsi_dcs_get_display_brightness(dsi, &brightness);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +     bl_value[0] = brightness & 0xff;
>> +     bl_value[1] = brightness >> 8;
>> +
>> +     return bl_value[0];
>> +}
>
> Why not simply return "brightness & 0xff" here?
>
>> +static int dsi_dcs_bl_update_status(struct backlight_device *bl)
>> +{
>> +     struct mipi_dsi_device *dsi = bl_get_data(bl);
>> +     int ret;
>> +     u16 brightness = bl->props.brightness;
>
> There's no need for this temporary variable.
>
>> +
>> +     dsi->mode_flags &= ~MIPI_DSI_MODE_LPM;
>> +
>> +     ret = mipi_dsi_dcs_set_display_brightness(dsi, brightness);
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     dsi->mode_flags |= MIPI_DSI_MODE_LPM;
>> +
>> +     return 0;
>> +}
> [...]
>> +struct backlight_device
>> +             *drm_panel_create_dsi_backlight(struct mipi_dsi_device *dsi)
>
> Your indentation is wrong here. The * should go on the same line as the
> type, and the function name should start in column 1.
>
>> +{
>> +     struct device *dev = &dsi->dev;
>> +     struct backlight_properties props;
>> +
>> +     memset(&props, 0, sizeof(props));
>> +     props.type = BACKLIGHT_RAW;
>> +     props.brightness = PANEL_MAX_BRIGHTNESS;
>> +     props.max_brightness = PANEL_MAX_BRIGHTNESS;
>
> Just use 255 for the maximum and default brightness here.
>
>> +static int jdi_panel_add(struct jdi_panel *jdi)
>> +{
>> +     struct device *dev = &jdi->dsi->dev;
>> +     struct regulator_bulk_data *s = jdi->supplies;
>> +     int num = PANEL_DEV_REGULATOR_MAX;
>
> Again, no need for these two temporary variables.
>
>> +     int i, ret;
>
> i should be unsigned int.
>
>> +
>> +     jdi->mode = &default_mode;
>> +
>> +     for (i = 0; i < num; i++)
>> +             s[i].supply = regs[i];
>> +
>> +     ret = devm_regulator_bulk_get(dev, num, s);
>> +     if (ret < 0) {
>> +             dev_err(dev, "%s: failed to init regulator, ret=%d\n",
>> +                     __func__, ret);
>> +             return ret;
>> +     }
>> +
>> +     jdi->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
>> +     if (IS_ERR(jdi->reset_gpio)) {
>> +             dev_err(dev, "cannot get reset-gpios %ld\n",
>> +                     PTR_ERR(jdi->reset_gpio));
>
> This is a third variant of error reporting. Please stick to one.
>
>> +             jdi->reset_gpio = NULL;
>> +     } else {
>> +             gpiod_direction_output(jdi->reset_gpio, 0);
>> +     }
>> +
>> +     jdi->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
>> +     if (IS_ERR(jdi->enable_gpio)) {
>> +             dev_err(dev, "cannot get enable-gpio %ld\n",
>> +                     PTR_ERR(jdi->enable_gpio));
>> +             jdi->enable_gpio = NULL;
>> +     } else {
>> +             gpiod_direction_output(jdi->enable_gpio, 0);
>> +     }
>> +
>> +     jdi->backlight = drm_panel_create_dsi_backlight(jdi->dsi);
>
> You should check for errors here.
>
>> +MODULE_AUTHOR("Vinay Simha BN <simhavcs@...il.com>");
>> +MODULE_DESCRIPTION("JDI WUXGA LT070ME05000 DSI video mode panel driver");
>
> The commit message names this "JDI LT070ME05000 WUXGA", please use the
> same here.
>
> Thierry



-- 
Regards,

Vinay Simha.B.N.

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