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Commit 61f11699 authored by Keith Packard's avatar Keith Packard Committed by Dave Airlie
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drm: Eliminate magic I2C frobbing when reading EDID 



This code depends on the underlying I2C adapter using the bit-banging algo,
which may not be the case. If specific encoders require this mechanism, they
should build a custom I2C algo that implements this workaround, rather than
having it in the general path.

Signed-off-by: default avatarKeith Packard <keithp@keithp.com>
Signed-off-by: default avatarDave Airlie <airlied@redhat.com>
parent 7ff14559

drivers/gpu/drm/drm_edid.c

+1 −73
Original line number Diff line number Diff line
@@ -584,85 +584,13 @@ int drm_do_probe_ddc_edid(struct i2c_adapter *adapter, 
}

EXPORT_SYMBOL(drm_do_probe_ddc_edid);



/**

 * Get EDID information.

 *

 * \param adapter : i2c device adaptor.

 * \param buf     : EDID data buffer to be filled

 * \param len     : EDID data buffer length

 * \return 0 on success or -1 on failure.

 *

 * Initialize DDC, then fetch EDID information

 * by calling drm_do_probe_ddc_edid function.

 */

static int drm_ddc_read(struct i2c_adapter *adapter,

			unsigned char *buf, int len)

{

	struct i2c_algo_bit_data *algo_data = adapter->algo_data;

	int i, j;

	int ret = -1;



	algo_data->setscl(algo_data->data, 1);



	for (i = 0; i < 1; i++) {

		/* For some old monitors we need the

		 * following process to initialize/stop DDC

		 */

		algo_data->setsda(algo_data->data, 1);

		msleep(13);



		algo_data->setscl(algo_data->data, 1);

		for (j = 0; j < 5; j++) {

			msleep(10);

			if (algo_data->getscl(algo_data->data))

				break;

		}

		if (j == 5)

			continue;



		algo_data->setsda(algo_data->data, 0);

		msleep(15);

		algo_data->setscl(algo_data->data, 0);

		msleep(15);

		algo_data->setsda(algo_data->data, 1);

		msleep(15);



		/* Do the real work */

		ret = drm_do_probe_ddc_edid(adapter, buf, len);

		algo_data->setsda(algo_data->data, 0);

		algo_data->setscl(algo_data->data, 0);

		msleep(15);



		algo_data->setscl(algo_data->data, 1);

		for (j = 0; j < 10; j++) {

			msleep(10);

			if (algo_data->getscl(algo_data->data))

				break;

		}



		algo_data->setsda(algo_data->data, 1);

		msleep(15);

		algo_data->setscl(algo_data->data, 0);

		algo_data->setsda(algo_data->data, 0);

		if (ret == 0)

			break;

	}

	/* Release the DDC lines when done or the Apple Cinema HD display

	 * will switch off

	 */

	algo_data->setsda(algo_data->data, 1);

	algo_data->setscl(algo_data->data, 1);



	return ret;

}



static int drm_ddc_read_edid(struct drm_connector *connector,

			     struct i2c_adapter *adapter,

			     char *buf, int len)

{

	int ret;



	ret = drm_ddc_read(adapter, buf, len);

	ret = drm_do_probe_ddc_edid(adapter, buf, len);

	if (ret != 0) {

		dev_info(&connector->dev->pdev->dev, "%s: no EDID data\n",

			 drm_get_connector_name(connector));