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Message-ID: <kmmxqakarwohqse7iomcqwsrns7lt5xkp23tfw6ftvmqwvkttc@h4bm3ttlhrsc>
Date: Sat, 27 Jul 2024 00:53:22 -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: [PATCH v2 2/2] drm/tiny: Add driver for Sharp Memory LCD
On Sat, Jul 27, 2024 at 12:12:01AM GMT, Christophe JAILLET wrote:
> Le 26/07/2024 à 21:44, Alex Lanzano a écrit :
> > Add support for the monochrome Sharp Memory LCDs.
> >
> > Signed-off-by: Alex Lanzano <lanzano.alex-Re5JQEeQqe8AvxtiuMwx3w@...lic.gmane.org>
> > Co-developed-by: Mehdi Djait <mehdi.djait-LDxbnhwyfcJBDgjK7y7TUQ@...lic.gmane.org>
> > Signed-off-by: Mehdi Djait <mehdi.djait-LDxbnhwyfcJBDgjK7y7TUQ@...lic.gmane.org>
> > ---
> > MAINTAINERS | 7 +
> > drivers/gpu/drm/tiny/Kconfig | 20 +
> > drivers/gpu/drm/tiny/Makefile | 1 +
> > drivers/gpu/drm/tiny/sharp-memory.c | 726 ++++++++++++++++++++++++++++
> > 4 files changed, 754 insertions(+)
> > create mode 100644 drivers/gpu/drm/tiny/sharp-memory.c
> >
>
> Hi,
>
> below some other tiny comments, hoping it helps.
>
> Also "./scripts/checkpatch.pl --strict" gives some hints, should some be of
> interest.
>
Ah! Thank you. I'll be sure to use strict from now on
> > +static int sharp_memory_probe(struct spi_device *spi)
> > +{
> > + int ret;
> > + struct device *dev;
> > + struct sharp_memory_device *smd;
> > + enum sharp_memory_model model;
> > + 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;
>
> 6 times below, &spi->dev could be replaced by dev, to slightly simplify
> things.
>
> > + 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(&spi->dev, &sharp_memory_drm_driver,
> > + struct sharp_memory_device, drm);
>
> Missing error handling.
>
> > +
> > + 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 == NULL)
>
> Nitpick: if (!smd->enable_gpio)
>
> > + dev_warn(&spi->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
> > + *
> > + */
> > + smd->vcom = 0;
>
> Nitpick: devm_drm_dev_alloc() already zeroes the allocated memory. So this
> is useless. Unless you think it gives some useful hint, it could be removed.
>
> > + if (device_property_read_string(&spi->dev, "vcom-mode", &vcom_mode_str))
> > + return dev_err_probe(dev, -EINVAL,
> > + "Unable to find vcom-mode node in device tree\n");
> > +
> > + if (!strcmp("software", vcom_mode_str)) {
> > + smd->vcom_mode = SHARP_MEMORY_SOFTWARE_VCOM;
>
> ...
>
> > + 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);
> > + if (!smd->tx_buffer)
> > + return dev_err_probe(&spi->dev, -ENOMEM, "Unable to alloc tx buffer\n");
>
> There is no need to log a message for memory allocation failure.
> return -ENOMEM; should be just fine IMHO.
>
> > +
> > + 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,
>
> Nitpick: you could save 1 LoC if this is put at the end of the previous
> line.
>
> > + 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
>
>
I appreciate the review! I'll get these addressed in v3
Best regards,
Alex
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