Re: [Intel-gfx] [PATCH v2 1/4] drm: Add helper for DP++ adaptors

Jani Nikula
2016-05-03T07:46:26Z

On Mon, 02 May 2016, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Add a helper which aids in the identification of DP dual mode
> (aka. DP++) adaptors. There are several types of adaptors
> specified: type 1 DVI, type 1 HDMI, type 2 DVI, type 2 HDMI
>
> Type 1 adaptors have a max TMDS clock limit of 165MHz, type 2 adaptors
> may go as high as 300MHz and they provide a register informing the
> source device what the actual limit is. Supposedly also type 1 adaptors
> may optionally implement this register. This TMDS clock limit is the
> main reason why we need to identify these adaptors.
>
> Type 1 adaptors provide access to their internal registers and the sink
> DDC bus through I2C. Type 2 adaptors provide this access both via I2C
> and I2C-over-AUX. A type 2 source device may choose to implement either
> of these methods. If a source device implements the I2C-over-AUX
> method, then the driver will obviously need specific support for such
> adaptors since the port is driven like an HDMI port, but DDC
> communication happes over the AUX channel.
>
> This helper should be enough to identify the adaptor type (some
> type 1 DVI adaptors may be a slight exception) and the maximum TMDS
> clock limit. Another feature that may be available is control over
> the TMDS output buffers on the adaptor, possibly allowing for some
> power saving when the TMDS link is down.
>
> Other user controllable features that may be available in the adaptors
> are downstream i2c bus speed control when using i2c-over-aux, and
> some control over the CEC pin. I chose not to provide any helper
> functions for those since I have no use for them in i915 at this time.
> The rest of the registers in the adaptor are mostly just information,
> eg. IEEE OUI, hardware and firmware revision, etc.
>
> v2: Pass adaptor type to helper functions to ease driver implementation
> Fix a bunch of typoes (Paulo)
> Add DRM_DP_DUAL_MODE_UNKNOWN for the case where we don't (yet) know
> the type (Paulo)
> Reject 0x00 and 0xff DP_DUAL_MODE_MAX_TMDS_CLOCK values (Paulo)
> Adjust drm_dp_dual_mode_detect() type2 vs. type1 detection to
> ease future LSPCON enabling
> Remove the unused DP_DUAL_MODE_LAST_RESERVED define
>
> Cc: stable@vger.kernel.org
> Cc: Tore Anderson <tore@fud.no>
> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> Cc: Shashank Sharma <shashank.sharma@intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/Makefile | 2 +-
> drivers/gpu/drm/drm_dp_dual_mode_helper.c | 356 ++++++++++++++++++++++++++++++
> include/drm/drm_dp_dual_mode_helper.h | 83 +++++++
> 3 files changed, 440 insertions(+), 1 deletion(-)
> create mode 100644 drivers/gpu/drm/drm_dp_dual_mode_helper.c
> create mode 100644 include/drm/drm_dp_dual_mode_helper.h
>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 1a26b4eb1ce0..29f2ee9b9534 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -23,7 +23,7 @@ drm-$(CONFIG_AGP) += drm_agpsupport.o
>
> drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
> drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
> - drm_kms_helper_common.o
> + drm_kms_helper_common.o drm_dp_dual_mode_helper.o
>
> drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
> drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> diff --git a/drivers/gpu/drm/drm_dp_dual_mode_helper.c b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> new file mode 100644
> index 000000000000..949c0fbeb542
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_dp_dual_mode_helper.c
> @@ -0,0 +1,356 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/export.h>
> +#include <linux/i2c.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <drm/drm_dp_dual_mode_helper.h>
> +#include <drm/drmP.h>
> +
> +/**
> + * DOC: DP dual mode (aka. DP++) adaptor helpers
> + *
> + * Helper functions to deal with DP dual mode adaptors.
> + *
> + * Type 1:
> + * Adaptor registers (if any) and the sink DDC bus may be accessed via I2C.
> + *
> + * Type 2:
> + * Adaptor registers and sink DDC bus can be accessed either via I2C or
> + * I2C-over-AUX. Source devices may choose to implement either of these
> + * access methods.
> + */
> +
> +#define DP_DUAL_MODE_SLAVE_ADDRESS 0x40
> +
> +/**
> + * drm_dp_dual_mode_read - Read from the DP dual mode adaptor register(s)
> + * adapter: I2C adapter for the DDC bus
> + * offset: register offset
> + * buffer: buffer for return data
> + * size: sizo of the buffer

The parameters need to be prefixed with @ in kernel-doc. Same across the
patch series.

BR,
Jani.

> + *
> + * Reads @size bytes from the DP dual mode adaptor registers
> + * starting at @offset.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure
> + */
> +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
> + u8 offset, void *buffer, size_t size)
> +{
> + struct i2c_msg msgs[] = {
> + {
> + .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> + .flags = 0,
> + .len = 1,
> + .buf = &offset,
> + },
> + {
> + .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> + .flags = I2C_M_RD,
> + .len = size,
> + .buf = buffer,
> + },
> + };
> + int ret;
> +
> + ret = i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
> + if (ret < 0)
> + return ret;
> + if (ret != ARRAY_SIZE(msgs))
> + return -EPROTO;
> +
> + return 0;
> +}
> +
> +/**
> + * drm_dp_dual_mode_write - Write to the DP dual mode adaptor register(s)
> + * adapter: I2C adapter for the DDC bus
> + * offset: register offset
> + * buffer: buffer for write data
> + * size: sizo of the buffer
> + *
> + * Writes @size bytes to the DP dual mode adaptor registers
> + * starting at @offset.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure
> + */
> +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
> + u8 offset, const void *buffer, size_t size)
> +{
> + struct i2c_msg msg = {
> + .addr = DP_DUAL_MODE_SLAVE_ADDRESS,
> + .flags = 0,
> + .len = 1 + size,
> + .buf = NULL,
> + };
> + void *data;
> + int ret;
> +
> + data = kmalloc(msg.len, GFP_TEMPORARY);
> + if (!data)
> + return -ENOMEM;
> +
> + msg.buf = data;
> +
> + memcpy(data, &offset, 1);
> + memcpy(data + 1, buffer, size);
> +
> + ret = i2c_transfer(adapter, &msg, 1);
> +
> + kfree(data);
> +
> + if (ret < 0)
> + return ret;
> + if (ret != 1)
> + return -EPROTO;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_dual_mode_write);
> +
> +static bool is_hdmi_adaptor(const char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN])
> +{
> + static const char dp_dual_mode_hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] =
> + "DP-HDMI ADAPTOR\x04";
> +
> + return memcmp(hdmi_id, dp_dual_mode_hdmi_id,
> + sizeof(dp_dual_mode_hdmi_id)) == 0;
> +}
> +
> +static bool is_type2_adaptor(uint8_t adaptor_id)
> +{
> + return adaptor_id == (DP_DUAL_MODE_TYPE_TYPE2 |
> + DP_DUAL_MODE_REV_TYPE2);
> +}
> +
> +/**
> + * drm_dp_dual_mode_detect - Identify the DP dual mode adaptor
> + * adapter: I2C adapter for the DDC bus
> + *
> + * Attempt to identify the type of the DP dual mode adaptor used.
> + *
> + * Note that when the answer is @DRM_DP_DUAL_MODE_NONE it's not
> + * certain whether we're dealing with a native HDMI port or
> + * a type 1 DVI dual mode adaptor. The driver will have to use
> + * some other hardware/driver specific mechanism to make that
> + * distinction.
> + *
> + * Returns:
> + * The type of the DP dual mode adaptor used
> + */
> +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter)
> +{
> + char hdmi_id[DP_DUAL_MODE_HDMI_ID_LEN] = {};
> + uint8_t adaptor_id = 0x00;
> + ssize_t ret;
> +
> + /*
> + * Let's see if the adaptor is there the by reading the
> + * HDMI ID registers.
> + *
> + * Note that type 1 DVI adaptors are not required to implemnt
> + * any registers, and that presents a problem for detection.
> + * If the i2c transfer is nacked, we may or may not be dealing
> + * with a type 1 DVI adaptor. Some other mechanism of detecting
> + * the presence of the adaptor is required. One way would be
> + * to check the state of the CONFIG1 pin, Another method would
> + * simply require the driver to know whether the port is a DP++
> + * port or a native HDMI port. Both of these methods are entirely
> + * hardware/driver specific so we can't deal with them here.
> + */
> + ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_HDMI_ID,
> + hdmi_id, sizeof(hdmi_id));
> + if (ret)
> + return DRM_DP_DUAL_MODE_UNKNOWN;
> +
> + /*
> + * Sigh. Some (maybe all?) type 1 adaptors are broken and ack
> + * the offset but ignore it, and instead they just always return
> + * data from the start of the HDMI ID buffer. So for a broken
> + * type 1 HDMI adaptor a single byte read will always give us
> + * 0x44, and for a type 1 DVI adaptor it should give 0x00
> + * (assuming it implements any registers). Fortunately neither
> + * of those values will match the type 2 signature of the
> + * DP_DUAL_MODE_ADAPTOR_ID register so we can proceed with
> + * the type 2 adaptor detection safely even in the presence
> + * of broken type 1 adaptors.
> + */
> + ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_ADAPTOR_ID,
> + &adaptor_id, sizeof(adaptor_id));
> + if (ret == 0) {
> + if (is_type2_adaptor(adaptor_id) && is_hdmi_adaptor(hdmi_id))
> + return DRM_DP_DUAL_MODE_TYPE2_HDMI;
> + else if (is_type2_adaptor(adaptor_id))
> + return DRM_DP_DUAL_MODE_TYPE2_DVI;
> + }
> +
> + if (is_hdmi_adaptor(hdmi_id))
> + return DRM_DP_DUAL_MODE_TYPE1_HDMI;
> + else
> + return DRM_DP_DUAL_MODE_TYPE1_DVI;
> +}
> +EXPORT_SYMBOL(drm_dp_dual_mode_detect);
> +
> +/**
> + * drm_dp_dual_mode_max_tmds_clock - Max TMDS clock for DP dual mode adaptor
> + * type: DP dual mode adaptor type
> + * adapter: I2C adapter for the DDC bus
> + *
> + * Determine the max TMDS clock the adaptor supports based on the
> + * type of the dual mode adaptor and the DP_DUAL_MODE_MAX_TMDS_CLOCK
> + * register (on type2 adaptors). As some type 1 adaptors have
> + * problems with registers (see comments in drm_dp_dual_mode_detect())
> + * we don't read the register on those, instead we simply assume
> + * a 165 MHz limit based on the specification.
> + *
> + * Returns:
> + * Maximum supported TMDS clock rate for the DP dual mode adaptor in kHz.
> + */
> +int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter)
> +{
> + uint8_t max_tmds_clock;
> + ssize_t ret;
> +
> + /* native HDMI so no limit */
> + if (type == DRM_DP_DUAL_MODE_NONE)
> + return 0;
> +
> + /*
> + * Type 1 adaptors are limited to 165MHz
> + * Type 2 adaptors can tells us their limit
> + */
> + if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
> + return 165000;
> +
> + ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_MAX_TMDS_CLOCK,
> + &max_tmds_clock, sizeof(max_tmds_clock));
> + if (ret || max_tmds_clock == 0x00 || max_tmds_clock == 0xff)
> + return 165000;
> +
> + return max_tmds_clock * 5000 / 2;
> +}
> +EXPORT_SYMBOL(drm_dp_dual_mode_max_tmds_clock);
> +
> +/**
> + * drm_dp_dual_mode_get_tmds_output - Get the state of the TMDS output buffers in the DP dual mode adaptor
> + * type: DP dual mode adaptor type
> + * adapter: I2C adapter for the DDC bus
> + * enabled: current state of the TMDS output buffers
> + *
> + * Get the state of the TMDS output buffers in the adaptor. For
> + * type2 adaptors this is queried from the DP_DUAL_MODE_TMDS_OEN
> + * register. As some type 1 adaptors have problems with registers
> + * (see comments in drm_dp_dual_mode_detect()) we don't read the
> + * register on those, instead we simply assume that the buffers
> + * are always enabled.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure
> + */
> +int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter,
> + bool *enabled)
> +{
> + uint8_t tmds_oen;
> + ssize_t ret;
> +
> + if (type < DRM_DP_DUAL_MODE_TYPE2_DVI) {
> + *enabled = true;
> + return 0;
> + }
> +
> + ret = drm_dp_dual_mode_read(adapter, DP_DUAL_MODE_TMDS_OEN,
> + &tmds_oen, sizeof(tmds_oen));
> + if (ret)
> + return ret;
> +
> + *enabled = !(tmds_oen & DP_DUAL_MODE_TMDS_DISABLE);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_dual_mode_get_tmds_output);
> +
> +/**
> + * drm_dp_dual_mode_set_tmds_output - Enable/disable TMDS output buffers in the DP dual mode adaptor
> + * type: DP dual mode adaptor type
> + * adapter: I2C adapter for the DDC bus
> + * enable: enable (as opposed to disable) the TMDS output buffers
> + *
> + * Set the state of the TMDS output buffers in the adaptor. For
> + * type2 this is set via the DP_DUAL_MODE_TMDS_OEN register. As
> + * some type 1 adaptors have problems with registers (see comments
> + * in drm_dp_dual_mode_detect()) we avoid touching the register,
> + * making this function a no-op on type 1 adaptors.
> + *
> + * Returns:
> + * 0 on success, negative error code on failure
> + */
> +int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter, bool enable)
> +{
> + uint8_t tmds_oen = enable ? 0 : DP_DUAL_MODE_TMDS_DISABLE;
> + ssize_t ret;
> +
> + if (type < DRM_DP_DUAL_MODE_TYPE2_DVI)
> + return 0;
> +
> + ret = drm_dp_dual_mode_write(adapter, DP_DUAL_MODE_TMDS_OEN,
> + &tmds_oen, sizeof(tmds_oen));
> + if (ret)
> + return ret;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_dual_mode_set_tmds_output);
> +
> +/**
> + * drm_dp_get_dual_mode_type_name - Get the name of the DP dual mode adaptor type as a string
> + * type: DP dual mode adaptor type
> + *
> + * Returns:
> + * String representation of the DP dual mode adaptor type
> + */
> +const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type)
> +{
> + switch (type) {
> + case DRM_DP_DUAL_MODE_NONE:
> + return "none";
> + case DRM_DP_DUAL_MODE_TYPE1_DVI:
> + return "type 1 DVI";
> + case DRM_DP_DUAL_MODE_TYPE1_HDMI:
> + return "type 1 HDMI";
> + case DRM_DP_DUAL_MODE_TYPE2_DVI:
> + return "type 2 DVI";
> + case DRM_DP_DUAL_MODE_TYPE2_HDMI:
> + return "type 2 HDMI";
> + default:
> + WARN_ON(type != DRM_DP_DUAL_MODE_UNKNOWN);
> + return "unknown";
> + }
> +}
> +EXPORT_SYMBOL(drm_dp_get_dual_mode_type_name);
> diff --git a/include/drm/drm_dp_dual_mode_helper.h b/include/drm/drm_dp_dual_mode_helper.h
> new file mode 100644
> index 000000000000..b4603b9fc03d
> --- /dev/null
> +++ b/include/drm/drm_dp_dual_mode_helper.h
> @@ -0,0 +1,83 @@
> +/*
> + * Copyright © 2016 Intel Corporation
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice shall be included in
> + * all copies or substantial portions of the Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
> + * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
> + * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
> + * OTHER DEALINGS IN THE SOFTWARE.
> + */
> +
> +#ifndef DRM_DP_DUAL_MODE_HELPER_H
> +#define DRM_DP_DUAL_MODE_HELPER_H
> +
> +#include <linux/types.h>
> +
> +/*
> + * Optional for type 1 DVI adaptors
> + * Mandatory for type 1 HDMI and type 2 adators
> + */
> +#define DP_DUAL_MODE_HDMI_ID 0x00 /* 00-0f */
> +#define DP_DUAL_MODE_HDMI_ID_LEN 16
> +/*
> + * Optional for type 1 adaptors
> + * Mandatory for type 2 adators
> + */
> +#define DP_DUAL_MODE_ADAPTOR_ID 0x10
> +#define DP_DUAL_MODE_REV_MASK 0x07
> +#define DP_DUAL_MODE_REV_TYPE2 0x00
> +#define DP_DUAL_MODE_TYPE_MASK 0xf0
> +#define DP_DUAL_MODE_TYPE_TYPE2 0xa0
> +#define DP_DUAL_MODE_IEEE_OUI 0x11 /* 11-13*/
> +#define DP_DUAL_IEEE_OUI_LEN 3
> +#define DP_DUAL_DEVICE_ID 0x14 /* 14-19 */
> +#define DP_DUAL_DEVICE_ID_LEN 6
> +#define DP_DUAL_MODE_HARDWARE_REV 0x1a
> +#define DP_DUAL_MODE_FIRMWARE_MAJOR_REV 0x1b
> +#define DP_DUAL_MODE_FIRMWARE_MINOR_REV 0x1c
> +#define DP_DUAL_MODE_MAX_TMDS_CLOCK 0x1d
> +#define DP_DUAL_MODE_I2C_SPEED_CAP 0x1e
> +#define DP_DUAL_MODE_TMDS_OEN 0x20
> +#define DP_DUAL_MODE_TMDS_DISABLE 0x01
> +#define DP_DUAL_MODE_HDMI_PIN_CTRL 0x21
> +#define DP_DUAL_MODE_CEC_ENABLE 0x01
> +#define DP_DUAL_MODE_I2C_SPEED_CTRL 0x22
> +
> +struct i2c_adapter;
> +
> +ssize_t drm_dp_dual_mode_read(struct i2c_adapter *adapter,
> + u8 offset, void *buffer, size_t size);
> +ssize_t drm_dp_dual_mode_write(struct i2c_adapter *adapter,
> + u8 offset, const void *buffer, size_t size);
> +
> +enum drm_dp_dual_mode_type {
> + DRM_DP_DUAL_MODE_NONE,
> + DRM_DP_DUAL_MODE_UNKNOWN,
> + DRM_DP_DUAL_MODE_TYPE1_DVI,
> + DRM_DP_DUAL_MODE_TYPE1_HDMI,
> + DRM_DP_DUAL_MODE_TYPE2_DVI,
> + DRM_DP_DUAL_MODE_TYPE2_HDMI,
> +};
> +
> +enum drm_dp_dual_mode_type drm_dp_dual_mode_detect(struct i2c_adapter *adapter);
> +int drm_dp_dual_mode_max_tmds_clock(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter);
> +int drm_dp_dual_mode_get_tmds_output(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter, bool *enabled);
> +int drm_dp_dual_mode_set_tmds_output(enum drm_dp_dual_mode_type type,
> + struct i2c_adapter *adapter, bool enable);
> +const char *drm_dp_get_dual_mode_type_name(enum drm_dp_dual_mode_type type);
> +
> +#endif

--
Jani Nikula, Intel Open Source Technology Center
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