Re: [PATCH v4 1/6] drm: Add SCDC helpers

Sharma, Shashank
2017-02-23T03:21:03Z

Thanks for the review Ville, my comments inline.

Regards

Shashank

On 2/22/2017 10:39 PM, Ville Syrjälä wrote:
> On Wed, Feb 22, 2017 at 06:48:26PM +0530, 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.
>>
>> V2: Rebase.
>> V3: Added R-B from Jose.
>> V4: Rebase
>>
>> Signed-off-by: Thierry Reding <treding@nvidia.com>
>> Signed-off-by: Shashank Sharma <shashank.sharma@intel.com>
>> Reviewed-by: Jose Abreu <joabreu@synopsys.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,
>> + .buf = &offset,
>> + }, {
>> + .addr = SCDC_I2C_SLAVE_ADDRESS,
>> + .flags = I2C_M_RD,
>> + .len = size,
>> + .buf = buffer,
>> + }
>> + };
>> +
>> + return i2c_transfer(adapter, msgs, ARRAY_SIZE(msgs));
> That still disagrees with the documentation. I would suggest doing what
> the DP dual mode helper does.
Sure, I guess this is about how we are handling the return values from
I2C layer, I will change it
the way its handled in drm_dp_dual_mode functions
>
>> +}
>> +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,
>> + .buf = NULL,
>> + };
>> + void *data;
>> + int err;
>> +
>> + data = kmalloc(1 + size, GFP_TEMPORARY);
>> + if (!data)
>> + return -ENOMEM;
>> +
>> + msg.buf = data;
>> +
>> + memcpy(data, &offset, sizeof(offset));
>> + memcpy(data + 1, buffer, size);
>> +
>> + 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)
> We don't usually define macros like this to extract information from the
> register. It's easy to confuse them with the normal macros for setting
> bits.
How about if I add another sub macro called _MAJOR, and use it like this:

#define _MAJOR(x) (x & 0xf)
#define SCDC_DEVICE_HARDWARE_REVISION_MAJOR(x) (_MAJOR((x) >> 4))

Or will you prefer no macro for this job at all ?

- Shashank
>> +
>> +#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
>> --
>> 1.9.1