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path: root/drivers/gpu/drm/drm_dp_helper.c
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Diffstat (limited to 'drivers/gpu/drm/drm_dp_helper.c')
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c207
1 files changed, 207 insertions, 0 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
new file mode 100644
index 000000000000..bb4eaf60117f
--- /dev/null
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -0,0 +1,207 @@
+/*
+ * Copyright © 2009 Keith Packard
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission. The copyright holders make no representations
+ * about the suitability of this software for any purpose. It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/sched.h>
+#include <linux/i2c.h>
+#include <drm/drm_dp_helper.h>
+#include <drm/drmP.h>
+
+/* Run a single AUX_CH I2C transaction, writing/reading data as necessary */
+static int
+i2c_algo_dp_aux_transaction(struct i2c_adapter *adapter, int mode,
+ uint8_t write_byte, uint8_t *read_byte)
+{
+ struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
+ int ret;
+
+ ret = (*algo_data->aux_ch)(adapter, mode,
+ write_byte, read_byte);
+ return ret;
+}
+
+/*
+ * I2C over AUX CH
+ */
+
+/*
+ * Send the address. If the I2C link is running, this 'restarts'
+ * the connection with the new address, this is used for doing
+ * a write followed by a read (as needed for DDC)
+ */
+static int
+i2c_algo_dp_aux_address(struct i2c_adapter *adapter, u16 address, bool reading)
+{
+ struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
+ int mode = MODE_I2C_START;
+ int ret;
+
+ if (reading)
+ mode |= MODE_I2C_READ;
+ else
+ mode |= MODE_I2C_WRITE;
+ algo_data->address = address;
+ algo_data->running = true;
+ ret = i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
+ return ret;
+}
+
+/*
+ * Stop the I2C transaction. This closes out the link, sending
+ * a bare address packet with the MOT bit turned off
+ */
+static void
+i2c_algo_dp_aux_stop(struct i2c_adapter *adapter, bool reading)
+{
+ struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
+ int mode = MODE_I2C_STOP;
+
+ if (reading)
+ mode |= MODE_I2C_READ;
+ else
+ mode |= MODE_I2C_WRITE;
+ if (algo_data->running) {
+ (void) i2c_algo_dp_aux_transaction(adapter, mode, 0, NULL);
+ algo_data->running = false;
+ }
+}
+
+/*
+ * Write a single byte to the current I2C address, the
+ * the I2C link must be running or this returns -EIO
+ */
+static int
+i2c_algo_dp_aux_put_byte(struct i2c_adapter *adapter, u8 byte)
+{
+ struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
+ int ret;
+
+ if (!algo_data->running)
+ return -EIO;
+
+ ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_WRITE, byte, NULL);
+ return ret;
+}
+
+/*
+ * Read a single byte from the current I2C address, the
+ * I2C link must be running or this returns -EIO
+ */
+static int
+i2c_algo_dp_aux_get_byte(struct i2c_adapter *adapter, u8 *byte_ret)
+{
+ struct i2c_algo_dp_aux_data *algo_data = adapter->algo_data;
+ int ret;
+
+ if (!algo_data->running)
+ return -EIO;
+
+ ret = i2c_algo_dp_aux_transaction(adapter, MODE_I2C_READ, 0, byte_ret);
+ return ret;
+}
+
+static int
+i2c_algo_dp_aux_xfer(struct i2c_adapter *adapter,
+ struct i2c_msg *msgs,
+ int num)
+{
+ int ret = 0;
+ bool reading = false;
+ int m;
+ int b;
+
+ for (m = 0; m < num; m++) {
+ u16 len = msgs[m].len;
+ u8 *buf = msgs[m].buf;
+ reading = (msgs[m].flags & I2C_M_RD) != 0;
+ ret = i2c_algo_dp_aux_address(adapter, msgs[m].addr, reading);
+ if (ret < 0)
+ break;
+ if (reading) {
+ for (b = 0; b < len; b++) {
+ ret = i2c_algo_dp_aux_get_byte(adapter, &buf[b]);
+ if (ret < 0)
+ break;
+ }
+ } else {
+ for (b = 0; b < len; b++) {
+ ret = i2c_algo_dp_aux_put_byte(adapter, buf[b]);
+ if (ret < 0)
+ break;
+ }
+ }
+ if (ret < 0)
+ break;
+ }
+ if (ret >= 0)
+ ret = num;
+ i2c_algo_dp_aux_stop(adapter, reading);
+ DRM_DEBUG_KMS("dp_aux_xfer return %d\n", ret);
+ return ret;
+}
+
+static u32
+i2c_algo_dp_aux_functionality(struct i2c_adapter *adapter)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
+ I2C_FUNC_SMBUS_READ_BLOCK_DATA |
+ I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
+ I2C_FUNC_10BIT_ADDR;
+}
+
+static const struct i2c_algorithm i2c_dp_aux_algo = {
+ .master_xfer = i2c_algo_dp_aux_xfer,
+ .functionality = i2c_algo_dp_aux_functionality,
+};
+
+static void
+i2c_dp_aux_reset_bus(struct i2c_adapter *adapter)
+{
+ (void) i2c_algo_dp_aux_address(adapter, 0, false);
+ (void) i2c_algo_dp_aux_stop(adapter, false);
+}
+
+static int
+i2c_dp_aux_prepare_bus(struct i2c_adapter *adapter)
+{
+ adapter->algo = &i2c_dp_aux_algo;
+ adapter->retries = 3;
+ i2c_dp_aux_reset_bus(adapter);
+ return 0;
+}
+
+int
+i2c_dp_aux_add_bus(struct i2c_adapter *adapter)
+{
+ int error;
+
+ error = i2c_dp_aux_prepare_bus(adapter);
+ if (error)
+ return error;
+ error = i2c_add_adapter(adapter);
+ return error;
+}
+EXPORT_SYMBOL(i2c_dp_aux_add_bus);

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