Hi Paul.
On Mon, Jul 27, 2020 at 06:46:10PM +0200, Paul Cercueil wrote:
> This driver will register a DBI host driver for panels connected over
> SPI.
So this is actually a MIPI DBI host driver.
I personally would love to have added mipi_ in the names - to make it
all more explicit.
But maybe that just because I get confused on all the acronyms.
Some details in the following. Will try to find some more time so I can
grasp the full picture. The following was just my low-level notes for
now.
Sam
>
> DBI types c1 and c3 are supported. C1 is a SPI protocol with 9 bits per
> word, with the data/command information in the 9th (MSB) bit. C3 is a
> SPI protocol with 8 bits per word, with the data/command information
> carried by a separate GPIO.
We did not have any define to distingush between DBI_C1 and DBI_c3:
+/* MIPI bus types */
+#define MIPI_DEVICE_TYPE_DSI BIT(0)
+#define MIPI_DEVICE_TYPE_DBI_SPI_MODE1 BIT(1)
+#define MIPI_DEVICE_TYPE_DBI_SPI_MODE2 BIT(2)
+#define MIPI_DEVICE_TYPE_DBI_SPI_MODE3 BIT(3)
+#define MIPI_DEVICE_TYPE_DBI_M6800 BIT(4)
+#define MIPI_DEVICE_TYPE_DBI_I8080 BIT(5)
Is this on purpose?
I had assumed the host should tell what it supports and the device should
tell what it wanted.
So if the host did not support DBI_C3 and device wants it - then we
could give up early.
>
> Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/bridge/Kconfig | 8 +
> drivers/gpu/drm/bridge/Makefile | 1 +
> drivers/gpu/drm/bridge/dbi-spi.c | 261 +++++++++++++++++++++++++++++++
This is no bridge driver - so does not belong in the bridge
directory.
gpu/drm/drm_mipi_dbi_spi.c?
> 3 files changed, 270 insertions(+)
> create mode 100644 drivers/gpu/drm/bridge/dbi-spi.c
>
> diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> index c7f0dacfb57a..ed38366847c1 100644
> --- a/drivers/gpu/drm/bridge/Kconfig
> +++ b/drivers/gpu/drm/bridge/Kconfig
> @@ -219,6 +219,14 @@ config DRM_TI_TPD12S015
> Texas Instruments TPD12S015 HDMI level shifter and ESD protection
> driver.
>
> +config DRM_MIPI_DBI_SPI
> + tristate "SPI host support for MIPI DBI"
> + depends on OF && SPI
> + select DRM_MIPI_DSI
> + select DRM_MIPI_DBI
> + help
> + Driver to support DBI over SPI.
> +
> source "drivers/gpu/drm/bridge/analogix/Kconfig"
>
> source "drivers/gpu/drm/bridge/adv7511/Kconfig"
> diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
> index 7d7c123a95e4..c2c522c2774f 100644
> --- a/drivers/gpu/drm/bridge/Makefile
> +++ b/drivers/gpu/drm/bridge/Makefile
> @@ -20,6 +20,7 @@ obj-$(CONFIG_DRM_I2C_ADV7511) += adv7511/
> obj-$(CONFIG_DRM_TI_SN65DSI86) += ti-sn65dsi86.o
> obj-$(CONFIG_DRM_TI_TFP410) += ti-tfp410.o
> obj-$(CONFIG_DRM_TI_TPD12S015) += ti-tpd12s015.o
> +obj-$(CONFIG_DRM_MIPI_DBI_SPI) += dbi-spi.o
mipi_dbi_spi.o would be nice...
> obj-$(CONFIG_DRM_NWL_MIPI_DSI) += nwl-dsi.o
>
> obj-y += analogix/
> diff --git a/drivers/gpu/drm/bridge/dbi-spi.c b/drivers/gpu/drm/bridge/dbi-spi.c
> new file mode 100644
> index 000000000000..1060b8f95fba
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/dbi-spi.c
> @@ -0,0 +1,261 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * MIPI Display Bus Interface (DBI) SPI support
> + *
> + * Copyright 2016 Noralf Trønnes
> + * Copyright 2020 Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> + */
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +
> +#include <drm/drm_mipi_dbi.h>
> +#include <drm/drm_mipi_dsi.h>
> +
> +#include <video/mipi_display.h>
> +
> +struct dbi_spi {
> + struct mipi_dsi_host host;
It is very confusing that the mipi_dbi_spi driver uses a dsi_host.
It clashes in my head - and then reviewing it not easy.
> + struct mipi_dsi_host_ops host_ops;
const?
> +
> + struct spi_device *spi;
> + struct gpio_desc *dc;
> + struct mutex cmdlock;
> +
> + unsigned int current_bus_type;
> +
> + /**
> + * @tx_buf9: Buffer used for Option 1 9-bit conversion
> + */
> + void *tx_buf9;
> +
> + /**
> + * @tx_buf9_len: Size of tx_buf9.
> + */
> + size_t tx_buf9_len;
> +};
> +
> +static inline struct dbi_spi *host_to_dbi_spi(struct mipi_dsi_host *host)
> +{
> + return container_of(host, struct dbi_spi, host);
> +}
> +
> +static ssize_t dbi_spi1_transfer(struct mipi_dsi_host *host,
> + const struct mipi_dsi_msg *msg)
> +{
> + struct dbi_spi *dbi = host_to_dbi_spi(host);
> + struct spi_device *spi = dbi->spi;
> + struct spi_transfer tr = {
> + .bits_per_word = 9,
> + };
> + const u8 *src8 = msg->tx_buf;
> + struct spi_message m;
> + size_t max_chunk, chunk;
> + size_t len = msg->tx_len;
> + bool cmd_byte = true;
> + unsigned int i;
> + u16 *dst16;
> + int ret;
> +
> + tr.speed_hz = mipi_dbi_spi_cmd_max_speed(spi, len);
> + dst16 = dbi->tx_buf9;
> +
> + max_chunk = min(dbi->tx_buf9_len / 2, len);
Hmm, this looks not right. We limit the max_chunk to 8K here.
We learned the other day that we count in bytes.
OR did I miss something?
> +
> + spi_message_init_with_transfers(&m, &tr, 1);
> + tr.tx_buf = dst16;
> +
> + while (len) {
> + chunk = min(len, max_chunk);
> +
> + for (i = 0; i < chunk; i++) {
> + dst16[i] = *src8++;
> +
> + /* Bit 9: 0 means command, 1 means data */
> + if (!cmd_byte)
> + dst16[i] |= BIT(9);
> +
> + cmd_byte = false;
> + }
> +
> + tr.len = chunk * 2;
> + len -= chunk;
> +
> + ret = spi_sync(spi, &m);
> + if (ret)
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static ssize_t dbi_spi3_transfer(struct mipi_dsi_host *host,
> + const struct mipi_dsi_msg *msg)
> +{
> + struct dbi_spi *dbi = host_to_dbi_spi(host);
> + struct spi_device *spi = dbi->spi;
> + const u8 *buf = msg->tx_buf;
> + unsigned int bpw = 8;
> + u32 speed_hz;
> + ssize_t ret;
> +
> + /* for now we only support sending messages, not receiving */
> + if (msg->rx_len)
> + return -EINVAL;
> +
> + gpiod_set_value_cansleep(dbi->dc, 0);
> +
> + speed_hz = mipi_dbi_spi_cmd_max_speed(spi, 1);
> + ret = mipi_dbi_spi_transfer(spi, speed_hz, 8, buf, 1);
> + if (ret || msg->tx_len == 1)
> + return ret;
> +
> + if (buf[0] == MIPI_DCS_WRITE_MEMORY_START)
> + bpw = 16;
> +
> + gpiod_set_value_cansleep(dbi->dc, 1);
> + speed_hz = mipi_dbi_spi_cmd_max_speed(spi, msg->tx_len - 1);
> +
> + ret = mipi_dbi_spi_transfer(spi, speed_hz, bpw,
> + &buf[1], msg->tx_len - 1);
> + if (ret)
> + return ret;
> +
> + return msg->tx_len;
> +}
> +
> +static ssize_t dbi_spi_transfer(struct mipi_dsi_host *host,
> + const struct mipi_dsi_msg *msg)
> +{
> + struct dbi_spi *dbi = host_to_dbi_spi(host);
> +
> + switch (dbi->current_bus_type) {
> + case MIPI_DEVICE_TYPE_DBI_SPI_MODE1:
> + return dbi_spi1_transfer(host, msg);
> + case MIPI_DEVICE_TYPE_DBI_SPI_MODE3:
> + return dbi_spi3_transfer(host, msg);
> + default:
> + dev_err(&dbi->spi->dev, "Unknown transfer type\n");
> + return -EINVAL;
> + }
> +}
> +
> +static int dbi_spi_attach(struct mipi_dsi_host *host,
> + struct mipi_dsi_device *dsi)
> +{
> + struct dbi_spi *dbi = host_to_dbi_spi(host);
> +
> + dbi->current_bus_type = dsi->bus_type;
> +
> + if (dbi->current_bus_type == MIPI_DEVICE_TYPE_DBI_SPI_MODE1) {
> + dbi->tx_buf9_len = SZ_16K;
> +
> + dbi->tx_buf9 = kmalloc(dbi->tx_buf9_len, GFP_KERNEL);
> + if (!dbi->tx_buf9)
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +static int dbi_spi_detach(struct mipi_dsi_host *host,
> + struct mipi_dsi_device *dsi)
> +{
> + struct dbi_spi *dbi = host_to_dbi_spi(host);
> +
> + kfree(dbi->tx_buf9);
> + dbi->tx_buf9_len = 0;
> +
> + return 0; /* Nothing to do */
> +}
> +
> +static void dbi_spi_host_unregister(void *d)
> +{
> + mipi_dsi_host_unregister(d);
> +}
> +
> +static int dbi_spi_probe(struct spi_device *spi)
> +{
> + struct device *dev = &spi->dev;
> + struct mipi_dsi_device_info info = { };
> + struct mipi_dsi_device *dsi;
> + struct dbi_spi *dbi;
> + int ret;
> +
> + dbi = devm_kzalloc(dev, sizeof(*dbi), GFP_KERNEL);
> + if (!dbi)
> + return -ENOMEM;
> +
> + dbi->host.dev = dev;
> + dbi->host.ops = &dbi->host_ops;
> + dbi->spi = spi;
> + spi_set_drvdata(spi, dbi);
> +
> + dbi->dc = devm_gpiod_get_optional(dev, "dc", GPIOD_OUT_LOW);
> + if (IS_ERR(dbi->dc)) {
> + dev_err(dev, "Failed to get gpio 'dc'\n");
> + return PTR_ERR(dbi->dc);
> + }
> +
> + if (spi_is_bpw_supported(spi, 9))
> + dbi->host.bus_types |= MIPI_DEVICE_TYPE_DBI_SPI_MODE1;
> + if (dbi->dc)
> + dbi->host.bus_types |= MIPI_DEVICE_TYPE_DBI_SPI_MODE3;
> +
> + if (!dbi->host.bus_types) {
> + dev_err(dev, "Neither Type1 nor Type3 are supported\n");
> + return -EINVAL;
> + }
> +
> + dbi->host_ops.transfer = dbi_spi_transfer;
> + dbi->host_ops.attach = dbi_spi_attach;
> + dbi->host_ops.detach = dbi_spi_detach;
> +
> + mutex_init(&dbi->cmdlock);
> +
> + ret = mipi_dsi_host_register(&dbi->host);
> + if (ret) {
> + dev_err(dev, "Unable to register DSI host\n");
> + return ret;
> + }
> +
> + ret = devm_add_action_or_reset(dev, dbi_spi_host_unregister, &dbi->host);
> + if (ret)
> + return ret;
> +
> + /*
> + * Register our own node as a MIPI DSI device.
> + * This ensures that the panel driver will be probed.
> + */
> + info.channel = 0;
> + info.node = of_node_get(dev->of_node);
> +
> + dsi = mipi_dsi_device_register_full(&dbi->host, &info);
> + if (IS_ERR(dsi)) {
> + dev_err(dev, "Failed to add DSI device\n");
> + return PTR_ERR(dsi);
> + }
> +
> + return 0;
> +}
> +
> +static const struct of_device_id dbi_spi_of_match[] = {
> + { .compatible = "adafruit,yx240qv29" },
> + { .compatible = "leadtek,ltk035c5444t-spi" },
> + { }
Would it be better with a fall-back compatible like:
mipi,dbi-spi.
So the nodes must includes this compatible to be registered with
this driver?
> +};
> +MODULE_DEVICE_TABLE(of, dbi_spi_of_match);
> +
> +static struct spi_driver dbi_spi_driver = {
> + .driver = {
> + .name = "dbi-spi",
> + .of_match_table = dbi_spi_of_match,
> + },
> + .probe = dbi_spi_probe,
> +};
> +module_spi_driver(dbi_spi_driver);
> +
> +MODULE_DESCRIPTION("DBI SPI bus driver");
> +MODULE_AUTHOR("Paul Cercueil <paul@xxxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL");
> --
> 2.27.0
