Re: [PATCH v2 1/6] drm: Add SCDC helpers

Jose Abreu
2017-02-07T11:01:14Z

Hi Shashank,

Sorry for the late review.

On 06-02-2017 13:59, Shashank Sharma wrote:
> From: Thierry Reding <treding@nvidia.com>
>
> SCDC is a mechanism defined in the HDMI 2.0 specification that allows
> the source and sink devices to communicate.
>
> This commit introduces helpers to access the SCDC and provides the
> symbolic names for the various registers defined in the specification.
>
> Signed-off-by: Thierry Reding <treding@nvidia.com>
> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
> ---
> Documentation/gpu/drm-kms-helpers.rst | 12 ++++
> drivers/gpu/drm/Makefile | 3 +-
> drivers/gpu/drm/drm_scdc_helper.c | 111 ++++++++++++++++++++++++++++
> include/drm/drm_scdc_helper.h | 132 ++++++++++++++++++++++++++++++++++
> 4 files changed, 257 insertions(+), 1 deletion(-)
> create mode 100644 drivers/gpu/drm/drm_scdc_helper.c
> create mode 100644 include/drm/drm_scdc_helper.h
>
> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
> index 03040aa..7592756 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -217,6 +217,18 @@ EDID Helper Functions Reference
> .. kernel-doc:: drivers/gpu/drm/drm_edid.c
> :export:
>
> +SCDC Helper Functions Reference
> +===============================
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_scdc_helper.c
> + :doc: scdc helpers
> +
> +.. kernel-doc:: include/drm/drm_scdc_helper.h
> + :internal:
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_scdc_helper.c
> + :export:
> +
> Rectangle Utilities Reference
> =============================
>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 92de399..ad91cd9 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -31,7 +31,8 @@ drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
> drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
> drm_plane_helper.o drm_dp_mst_topology.o drm_atomic_helper.o \
> drm_kms_helper_common.o drm_dp_dual_mode_helper.o \
> - drm_simple_kms_helper.o drm_modeset_helper.o
> + drm_simple_kms_helper.o drm_modeset_helper.o \
> + drm_scdc_helper.o
>
> drm_kms_helper-$(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_scdc_helper.c b/drivers/gpu/drm/drm_scdc_helper.c
> new file mode 100644
> index 0000000..fe0e121
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_scdc_helper.c
> @@ -0,0 +1,111 @@
> +/*
> + * Copyright (c) 2015 NVIDIA Corporation. All rights reserved.
> + *
> + * 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, sub license,
> + * 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 (including the
> + * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS 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/slab.h>
> +
> +#include <drm/drm_scdc_helper.h>
> +
> +/**
> + * DOC: scdc helpers
> + *
> + * Status and Control Data Channel (SCDC) is a mechanism introduced by the
> + * HDMI 2.0 specification. It is a point-to-point protocol that allows the
> + * HDMI source and HDMI sink to exchange data. The same I2C interface that
> + * is used to access EDID serves as the transport mechanism for SCDC.
> + */
> +
> +#define SCDC_I2C_SLAVE_ADDRESS 0x54
> +
> +/**
> + * drm_scdc_read - read a block of data from SCDC
> + * @adapter: I2C controller
> + * @offset: start offset of block to read
> + * @buffer: return location for the block to read
> + * @size: size of the block to read
> + *
> + * Reads a block of data from SCDC, starting at a given offset.
> + *
> + * Returns:
> + * The number of bytes read from SCDC or a negative error code on failure.
> + */
> +ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer,
> + size_t size)
> +{
> + struct i2c_msg msgs[2] = {
> + {
> + .addr = SCDC_I2C_SLAVE_ADDRESS,
> + .flags = 0,
> + .len = 1,

.len = sizeof(offset) ?

> + .buf = &offset,
> + }, {
> + .addr = SCDC_I2C_SLAVE_ADDRESS,
> + .flags = I2C_M_RD,
> + .len = size,
> + .buf = buffer,
> + }
> + };
> +
> + return i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
> +}
> +EXPORT_SYMBOL(drm_scdc_read);
> +
> +/**
> + * drm_scdc_write - write a block of data to SCDC
> + * @adapter: I2C controller
> + * @offset: start offset of block to write
> + * @buffer: block of data to write
> + * @size: size of the block to write
> + *
> + * Writes a block of data to SCDC, starting at a given offset.
> + *
> + * Returns:
> + * The number of bytes written to SCDC or a negative error code on failure.
> + */
> +ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
> + const void *buffer, size_t size)
> +{
> + struct i2c_msg msg = {
> + .addr = SCDC_I2C_SLAVE_ADDRESS,
> + .flags = 0,
> + .len = 1 + size,

.len = sizeof(offset) + size ?

> + .buf = NULL,
> + };
> + void *data;
> + int err;
> +
> + data = kmalloc(1 + size, GFP_TEMPORARY);

Same as above.

> + if (!data)
> + return -ENOMEM;
> +
> + msg.buf = data;
> +
> + memcpy(data, &offset, sizeof(offset));
> + memcpy(data + 1, buffer, size);

Same as above.

Best regards,
Jose Miguel Abreu

> +
> + err = i2c_transfer(adapter, &msg, 1);
> +
> + kfree(data);
> +
> + return err;
> +}
> +EXPORT_SYMBOL(drm_scdc_write);
> diff --git a/include/drm/drm_scdc_helper.h b/include/drm/drm_scdc_helper.h
> new file mode 100644
> index 0000000..93b07bc
> --- /dev/null
> +++ b/include/drm/drm_scdc_helper.h
> @@ -0,0 +1,132 @@
> +/*
> + * Copyright (c) 2015 NVIDIA Corporation. All rights reserved.
> + *
> + * 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, sub license,
> + * 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 (including the
> + * next paragraph) 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 NON-INFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS 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_SCDC_HELPER_H
> +#define DRM_SCDC_HELPER_H
> +
> +#include <linux/i2c.h>
> +#include <linux/types.h>
> +
> +#define SCDC_SINK_VERSION 0x01
> +
> +#define SCDC_SOURCE_VERSION 0x02
> +
> +#define SCDC_UPDATE_0 0x10
> +#define SCDC_READ_REQUEST_TEST (1 << 2)
> +#define SCDC_CED_UPDATE (1 << 1)
> +#define SCDC_STATUS_UPDATE (1 << 0)
> +
> +#define SCDC_UPDATE_1 0x11
> +
> +#define SCDC_TMDS_CONFIG 0x20
> +#define SCDC_TMDS_BIT_CLOCK_RATIO_BY_40 (1 << 1)
> +#define SCDC_TMDS_BIT_CLOCK_RATIO_BY_10 (0 << 1)
> +#define SCDC_SCRAMBLING_ENABLE (1 << 0)
> +
> +#define SCDC_SCRAMBLER_STATUS 0x21
> +#define SCDC_SCRAMBLING_STATUS (1 << 0)
> +
> +#define SCDC_CONFIG_0 0x30
> +#define SCDC_READ_REQUEST_ENABLE (1 << 0)
> +
> +#define SCDC_STATUS_FLAGS_0 0x40
> +#define SCDC_CH2_LOCK (1 < 3)
> +#define SCDC_CH1_LOCK (1 < 2)
> +#define SCDC_CH0_LOCK (1 < 1)
> +#define SCDC_CH_LOCK_MASK (SCDC_CH2_LOCK | SCDC_CH1_LOCK | SCDC_CH0_LOCK)
> +#define SCDC_CLOCK_DETECT (1 << 0)
> +
> +#define SCDC_STATUS_FLAGS_1 0x41
> +
> +#define SCDC_ERR_DET_0_L 0x50
> +#define SCDC_ERR_DET_0_H 0x51
> +#define SCDC_ERR_DET_1_L 0x52
> +#define SCDC_ERR_DET_1_H 0x53
> +#define SCDC_ERR_DET_2_L 0x54
> +#define SCDC_ERR_DET_2_H 0x55
> +#define SCDC_CHANNEL_VALID (1 << 7)
> +
> +#define SCDC_ERR_DET_CHECKSUM 0x56
> +
> +#define SCDC_TEST_CONFIG_0 0xc0
> +#define SCDC_TEST_READ_REQUEST (1 << 7)
> +#define SCDC_TEST_READ_REQUEST_DELAY(x) ((x) & 0x7f)
> +
> +#define SCDC_MANUFACTURER_IEEE_OUI 0xd0
> +#define SCDC_MANUFACTURER_IEEE_OUI_SIZE 3
> +
> +#define SCDC_DEVICE_ID 0xd3
> +#define SCDC_DEVICE_ID_SIZE 8
> +
> +#define SCDC_DEVICE_HARDWARE_REVISION 0xdb
> +#define SCDC_DEVICE_HARDWARE_REVISION_MAJOR(x) (((x) >> 4) & 0xf)
> +#define SCDC_DEVICE_HARDWARE_REVISION_MINOR(x) (((x) >> 0) & 0xf)
> +
> +#define SCDC_DEVICE_SOFTWARE_MAJOR_REVISION 0xdc
> +#define SCDC_DEVICE_SOFTWARE_MINOR_REVISION 0xdd
> +
> +#define SCDC_MANUFACTURER_SPECIFIC 0xde
> +#define SCDC_MANUFACTURER_SPECIFIC_SIZE 34
> +
> +ssize_t drm_scdc_read(struct i2c_adapter *adapter, u8 offset, void *buffer,
> + size_t size);
> +ssize_t drm_scdc_write(struct i2c_adapter *adapter, u8 offset,
> + const void *buffer, size_t size);
> +
> +/**
> + * drm_scdc_readb - read a single byte from SCDC
> + * @adapter: I2C adapter
> + * @offset: offset of register to read
> + * @value: return location for the register value
> + *
> + * Reads a single byte from SCDC. This is a convenience wrapper around the
> + * drm_scdc_read() function.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +static inline int drm_scdc_readb(struct i2c_adapter *adapter, u8 offset,
> + u8 *value)
> +{
> + return drm_scdc_read(adapter, offset, value, sizeof(*value));
> +}
> +
> +/**
> + * drm_scdc_writeb - write a single byte to SCDC
> + * @adapter: I2C adapter
> + * @offset: offset of register to read
> + * @value: return location for the register value
> + *
> + * Writes a single byte to SCDC. This is a convenience wrapper around the
> + * drm_scdc_write() function.
> + *
> + * Returns:
> + * 0 on success or a negative error code on failure.
> + */
> +static inline int drm_scdc_writeb(struct i2c_adapter *adapter, u8 offset,
> + u8 value)
> +{
> + return drm_scdc_write(adapter, offset, &value, sizeof(value));
> +}
> +
> +#endif