Message-ID: <xjimc7o6lgaivockfugwfmdsae6fm7hz2cd4nvvwkuavabjjkd@kvo4alvvoqzl>
Date: Fri, 30 Aug 2024 10:26:11 -0400
From: Alex Lanzano <lanzano.alex@...il.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: airlied@...il.com, conor+dt@...nel.org, daniel@...ll.ch, 
	devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org, krzk+dt@...nel.org, 
	linux-kernel@...r.kernel.org, maarten.lankhorst@...ux.intel.com, mehdi.djait@...tlin.com, 
	mripard@...nel.org, robh@...nel.org, tzimmermann@...e.de
Subject: Re: [RESEND PATCH v4 2/2] drm/tiny: Add driver for Sharp Memory LCD

On Tue, Aug 20, 2024 at 08:53:07AM GMT, Christophe JAILLET wrote:
> Le 19/08/2024 à 23:49, Alex Lanzano a écrit :
> > Add support for the monochrome Sharp Memory LCDs.
> 
> Hi,
> 
> a few nitpick below, should thre be a v5.
> 
> ...
> 
> > +struct sharp_memory_device {
> > +	struct drm_device drm;
> > +	struct spi_device *spi;
> > +
> > +	const struct drm_display_mode *mode;
> > +
> > +	struct drm_crtc crtc;
> > +	struct drm_plane plane;
> > +	struct drm_encoder encoder;
> > +	struct drm_connector connector;
> > +
> > +	struct gpio_desc *enable_gpio;
> > +
> > +	struct task_struct *sw_vcom_signal;
> > +	struct pwm_device *pwm_vcom_signal;
> > +
> > +	enum sharp_memory_vcom_mode vcom_mode;
> > +	u8 vcom;
> > +
> > +	u32 pitch;
> > +	u32 tx_buffer_size;
> > +	u8 *tx_buffer;
> > +
> > +	/* When vcom_mode == "software" a kthread is used to
> > +	 * periodically send a 'maintain display' message over
> > +	 * spi. This mutex ensures tx_buffer access and spi bus
> > +	 * usage is synchronized in this case
> 
> This comment could take only 3 lines and still be with < 80 lines.
> A dot could also be added at the end of the 2nd sentence.
> 
> > +	 */
> > +	struct mutex tx_mutex;
> > +};
> 
> ...
> 
> > +static int sharp_memory_probe(struct spi_device *spi)
> > +{
> > +	int ret;
> > +	struct device *dev;
> > +	struct sharp_memory_device *smd;
> > +	struct drm_device *drm;
> > +	const char *vcom_mode_str;
> > +
> > +	ret = spi_setup(spi);
> > +	if (ret < 0)
> > +		return dev_err_probe(&spi->dev, ret, "Failed to setup spi device\n");
> > +
> > +	dev = &spi->dev;
> 
> If done earlier (when dev is declared?), it could already be used in the
> dev_err_probe() just above?
> 
> > +	if (!dev->coherent_dma_mask) {
> > +		ret = dma_coerce_mask_and_coherent(dev, DMA_BIT_MASK(32));
> > +		if (ret)
> > +			return dev_err_probe(dev, ret, "Failed to set dma mask\n");
> > +	}
> > +
> > +	smd = devm_drm_dev_alloc(dev, &sharp_memory_drm_driver,
> > +				 struct sharp_memory_device, drm);
> > +	if (!smd)
> > +		return -ENOMEM;
> > +
> > +	spi_set_drvdata(spi, smd);
> > +
> > +	smd->spi = spi;
> > +	drm = &smd->drm;
> > +	ret = drmm_mode_config_init(drm);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "Failed to initialize drm config\n");
> > +
> > +	smd->enable_gpio = devm_gpiod_get_optional(dev, "enable", GPIOD_OUT_HIGH);
> > +	if (!smd->enable_gpio)
> > +		dev_warn(dev, "Enable gpio not defined\n");
> > +
> > +	/*
> > +	 * VCOM is a signal that prevents DC bias from being built up in
> > +	 * the panel resulting in pixels being forever stuck in one state.
> > +	 *
> > +	 * This driver supports three different methods to generate this
> > +	 * signal depending on EXTMODE pin:
> > +	 *
> > +	 * software (EXTMODE = L) - This mode uses a kthread to
> > +	 * periodically send a "maintain display" message to the display,
> > +	 * toggling the vcom bit on and off with each message
> > +	 *
> > +	 * external (EXTMODE = H) - This mode relies on an external
> > +	 * clock to generate the signal on the EXTCOMM pin
> > +	 *
> > +	 * pwm (EXTMODE = H) - This mode uses a pwm device to generate
> > +	 * the signal on the EXTCOMM pin
> > +	 *
> > +	 */
> > +	if (device_property_read_string(&spi->dev, "sharp,vcom-mode", &vcom_mode_str))
> 
> just dev?
> 
> > +		return dev_err_probe(dev, -EINVAL,
> > +				     "Unable to find sharp,vcom-mode node in device tree\n");
> > +
> > +	if (!strcmp("software", vcom_mode_str)) {
> > +		smd->vcom_mode = SHARP_MEMORY_SOFTWARE_VCOM;
> > +
> > +	} else if (!strcmp("external", vcom_mode_str)) {
> > +		smd->vcom_mode = SHARP_MEMORY_EXTERNAL_VCOM;
> > +
> > +	} else if (!strcmp("pwm", vcom_mode_str)) {
> > +		smd->vcom_mode = SHARP_MEMORY_PWM_VCOM;
> > +		ret = sharp_memory_init_pwm_vcom_signal(smd);
> > +		if (ret)
> > +			return dev_err_probe(dev, ret,
> > +					     "Failed to initialize external COM signal\n");
> > +	} else {
> > +		return dev_err_probe(dev, -EINVAL, "Invalid value set for vcom-mode\n");
> > +	}
> > +
> > +	drm->mode_config.funcs = &sharp_memory_mode_config_funcs;
> > +	smd->mode = spi_get_device_match_data(spi);
> > +
> > +	smd->pitch = (SHARP_ADDR_PERIOD + smd->mode->hdisplay + SHARP_DUMMY_PERIOD) / 8;
> > +	smd->tx_buffer_size = (SHARP_MODE_PERIOD +
> > +			       (SHARP_ADDR_PERIOD + (smd->mode->hdisplay) + SHARP_DUMMY_PERIOD) *
> > +			       smd->mode->vdisplay) / 8;
> > +
> > +	smd->tx_buffer = devm_kzalloc(&spi->dev, smd->tx_buffer_size, GFP_KERNEL);
> 
> Just dev?
> 
> > +	if (!smd->tx_buffer)
> > +		return -ENOMEM;
> > +
> > +	mutex_init(&smd->tx_mutex);
> > +
> > +	drm->mode_config.min_width = smd->mode->hdisplay;
> > +	drm->mode_config.max_width = smd->mode->hdisplay;
> > +	drm->mode_config.min_height = smd->mode->vdisplay;
> > +	drm->mode_config.max_height = smd->mode->vdisplay;
> > +
> > +	ret = sharp_memory_pipe_init(drm, smd, sharp_memory_formats,
> > +				     ARRAY_SIZE(sharp_memory_formats),
> > +				     NULL);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "Failed to initialize display pipeline.\n");
> > +
> > +	drm_plane_enable_fb_damage_clips(&smd->plane);
> > +	drm_mode_config_reset(drm);
> > +
> > +	ret = drm_dev_register(drm, 0);
> > +	if (ret)
> > +		return dev_err_probe(dev, ret, "Failed to register drm device.\n");
> > +
> > +	drm_fbdev_dma_setup(drm, 0);
> > +
> > +	return 0;
> > +}
> 
> ...
> 
> CJ
> 

Thank you for the review! Will address in v5

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