Re: [PATCH 3/6] drm/bridge: Add SPI DBI host driver
From: Paul Cercueil
Date: Mon Jul 27 2020 - 17:10:51 EST
Hi Sam,
Le lun. 27 juil. 2020 à 22:31, Sam Ravnborg <sam@xxxxxxxxxxxx> 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@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.
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@xxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
--
2.27.0