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Date: Wed, 9 Feb 2022 17:12:29 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Javier Martinez Canillas <javierm@...hat.com>
Cc: linux-kernel@...r.kernel.org,
Thomas Zimmermann <tzimmermann@...e.de>,
Noralf Trønnes <noralf@...nnes.org>,
Maxime Ripard <maxime@...no.tech>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
linux-fbdev@...r.kernel.org,
Daniel Vetter <daniel.vetter@...ll.ch>,
Sam Ravnborg <sam@...nborg.org>,
dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...ux.ie>,
Lee Jones <lee.jones@...aro.org>,
Liam Girdwood <lgirdwood@...il.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Mark Brown <broonie@...nel.org>,
Maxime Ripard <mripard@...nel.org>,
Thierry Reding <thierry.reding@...il.com>,
Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>, linux-pwm@...r.kernel.org
Subject: Re: [PATCH v3 3/7] drm: Add driver for Solomon SSD130X OLED displays
On Wed, Feb 09, 2022 at 10:03:10AM +0100, Javier Martinez Canillas wrote:
> This adds a DRM driver for SSD1305, SSD1306, SSD1307 and SSD1309 Solomon
> OLED display controllers.
>
> It's only the core part of the driver and a bus specific driver is needed
> for each transport interface supported by the display controllers.
Thank you for the update, my comments below.
...
> source "drivers/gpu/drm/sprd/Kconfig"
>
> +source "drivers/gpu/drm/solomon/Kconfig"
'o' before 'p' ?
...
> obj-$(CONFIG_DRM_SPRD) += sprd/
> +obj-y += solomon/
Ditto ?
...
> +/*
> + * DRM driver for Solomon SSD130X OLED displays
Solomon SSD130x (with lower letter it's easy to read and realize that it's
not a model name).
> + * Copyright 2022 Red Hat Inc.
> + * Authors: Javier Martinez Canillas <javierm@...hat.com>
> + *
> + * Based on drivers/video/fbdev/ssd1307fb.c
> + * Copyright 2012 Free Electrons
> + */
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/property.h>
> +#include <linux/pwm.h>
> +#include <linux/regulator/consumer.h>
...
> +#define DRIVER_NAME "ssd130x"
> +#define DRIVER_DESC "DRM driver for Solomon SSD130X OLED displays"
> +#define DRIVER_DATE "20220131"
> +#define DRIVER_MAJOR 1
> +#define DRIVER_MINOR 0
Not sure it has a value when being defined. Only one string is reused and even
if hard coded twice linker will optimize it.
...
> +/*
> + * Helper to write command (SSD130X_COMMAND). The fist variadic argument
> + * is the command to write and the following are the command options.
> + */
> +static int ssd130x_write_cmd(struct ssd130x_device *ssd130x, int count,
> + /* u8 cmd, u8 option, ... */...)
> +{
> + va_list ap;
> + u8 value;
> + int ret;
> +
> + va_start(ap, count);
> +
> + do {
> + value = va_arg(ap, int);
> + ret = regmap_write(ssd130x->regmap, SSD130X_COMMAND, (u8)value);
> + if (ret)
> + goto out_end;
> + } while (--count);
> +
> +out_end:
> + va_end(ap);
> +
> + return ret;
Can bulk operation be used in the callers instead?
I have noticed that all of the callers are using
- 1 -- makes no sense at all, can be replaced with regmap_write()
- 2
- 3
Can be helpers for two and three arguments, with use of bulk call.
What do you think?
> +}
...
> +static void ssd130x_reset(struct ssd130x_device *ssd130x)
> +{
> + /* Reset the screen */
> + gpiod_set_value_cansleep(ssd130x->reset, 1);
> + udelay(4);
> + gpiod_set_value_cansleep(ssd130x->reset, 0);
> + udelay(4);
I don't remember if reset pin is mandatory. fbtft does
if (!gpiod->reset)
return;
...do reset...
> +}
...
> + if (ssd130x->reset)
A-ha, why not in the callee?
> + ssd130x_reset(ssd130x);
...
> + /* Set COM direction */
> + com_invdir = 0xc0 | ssd130x->com_invdir << 3;
Can 0xc0 and 3 be GENMASK()'ed and defined?
...
> + /* Set clock frequency */
> + dclk = ((ssd130x->dclk_div - 1) & 0xf) | (ssd130x->dclk_frq & 0xf) << 4;
GENMASK() ?
...
> + u32 mode = ((ssd130x->area_color_enable ? 0x30 : 0) |
> + (ssd130x->low_power ? 5 : 0));
With if's it will look better.
u32 mode = 0;
if (ssd130x->area_color_enable)
mode |= 0x30;
if (ssd130x->low_power)
mode |= 5;
...
> + /* Turn on the DC-DC Charge Pump */
> + chargepump = BIT(4) | (ssd130x->device_info->need_chargepump ? BIT(2) : 0);
Ditto.
...
> + for (i = 0; i < ARRAY_SIZE(ssd130x->lookup_table); ++i) {
i++ should work as well.
> + u8 val = ssd130x->lookup_table[i];
> +
> + if (val < 31 || val > 63)
> + dev_warn(ssd130x->dev,
> + "lookup table index %d value out of range 31 <= %d <= 63\n",
> + i, val);
> + ret = ssd130x_write_cmd(ssd130x, 1, val);
> + if (ret < 0)
> + return ret;
> + }
...
> + u8 *buf = NULL;
> +
Redundant blank line, not sure if checkpatch catches this.
> + struct drm_rect fullscreen = {
> + .x1 = 0,
> + .x2 = ssd130x->width,
> + .y1 = 0,
> + .y2 = ssd130x->height,
> + };
...
> +power_off:
out_power_off: ?
...
> + ret = PTR_ERR(ssd130x->vbat_reg);
> + if (ret == -ENODEV)
> + ssd130x->vbat_reg = NULL;
> + else
> + return dev_err_probe(dev, ret, "Failed to get VBAT regulator\n");
Can it be
ret = PTR_ERR(ssd130x->vbat_reg);
if (ret != -ENODEV)
return dev_err_probe(dev, ret, "Failed to get VBAT regulator\n");
ssd130x->vbat_reg = NULL;
?
...
> + ssd130x = devm_drm_dev_alloc(dev, &ssd130x_drm_driver,
> + struct ssd130x_device, drm);
> + if (IS_ERR(ssd130x)) {
> + dev_err(dev, "Failed to allocate DRM device: %d\n", ret);
> + return ssd130x;
return dev_err_probe() ?
> + }
...
> + bl = devm_backlight_device_register(dev, dev_name(dev), dev, ssd130x,
> + &ssd130xfb_bl_ops, NULL);
> + if (IS_ERR(bl)) {
> + ret = PTR_ERR(bl);
> + dev_err(dev, "Unable to register backlight device: %d\n", ret);
> + return ERR_PTR(ret);
Ditto.
> + }
...
> + ret = drm_dev_register(drm, 0);
> + if (ret) {
> + dev_err(dev, "DRM device register failed: %d\n", ret);
> + return ERR_PTR(ret);
Ditto.
> + }
...
I have feelings that half of my comments were ignored...
Maybe I missed the discussion(s).
--
With Best Regards,
Andy Shevchenko
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