Re: [PATCH 3/6] drm/bridge: Add SPI DBI host driver

Hi Sam,

Le lun. 27 juil. 2020 à 22:31, Sam Ravnborg sam@ravnborg.org a écrit :

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.

I can rename the driver and move it out of drm/bridge/, no problem.

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 understand the confusion. Here SPI_MODE1/3 actually mean SPI_C1/3. I will rename them.

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.

Well that's exactly what's done here - just with badly named macros :)

...

Signed-off-by: Paul Cercueil paul@crapouillou.net

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@crapouillou.net
• */

+#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.

From now on read all "mipi_dsi_*" as a MIPI DSI/DBI API. Renaming the API means a treewide patchset that touches many many files...

...

• 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?

We want to extend 8-bit values into 16-bit values, and we have a X-bytes output buffer for that, so the maximum input buffer size we can use is (X/2).

This code is the original algorithm in drm_mipi_dbi.c, I didn't change anything here (safe for the fix that was merged a couple of days ago to drm-misc-fixes).

...

• 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?

Ideally, it would be perfect, but unfortunately we cannot do that.

If a node has the following: compatible = "adafruit,yx240qv29", "mipi-dbi-spi";

Then Linux will probe only with the first compatible string since it has a driver for it. It will use the fallback string only if no driver matches the first string.

-Paul

...

+}; +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@crapouillou.net");

+MODULE_LICENSE("GPL");

2.27.0