Re: [RFC PATCH 6/7] drm: add support for DisplayPort CEC-Tunneling-over-AUX

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On Thu, May 25, 2017 at 05:06:25PM +0200, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> 
> This adds support for the DisplayPort CEC-Tunneling-over-AUX
> feature that is part of the DisplayPort 1.3 standard.
> 
> Unfortunately, not all DisplayPort/USB-C to HDMI adapters with a
> chip that has this capability actually hook up the CEC pin, so
> even though a CEC device is created, it may not actually work.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> ---
>  drivers/gpu/drm/Kconfig      |   3 +
>  drivers/gpu/drm/Makefile     |   1 +
>  drivers/gpu/drm/drm_dp_cec.c | 196 +++++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_helper.h  |  24 ++++++
>  4 files changed, 224 insertions(+)
>  create mode 100644 drivers/gpu/drm/drm_dp_cec.c
> 
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 78d7fc0ebb57..dd771ce8a3d0 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -120,6 +120,9 @@ config DRM_LOAD_EDID_FIRMWARE
>  	  default case is N. Details and instructions how to build your own
>  	  EDID data are given in Documentation/EDID/HOWTO.txt.
>  
> +config DRM_DP_CEC
> +	bool

We generally don't bother with a Kconfig for every little bit in drm, not
worth the trouble (yes I know there's some exceptions, but somehow they're
all from soc people). Just smash this into the KMS_HELPER one and live is
much easier for drivers. Also allows you to drop the dummy inline
functions.

The other nitpick: Pls kernel-doc the functions exported to drivers, and
then pull them into Documentation/gpu/drm-kms-helpers.rst, next to the
existing DP helper section.

Thanks, Daniel

> +
>  config DRM_TTM
>  	tristate
>  	depends on DRM && MMU
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 59f0f9b696eb..22f1a17dfc8a 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -34,6 +34,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_probe_helper.o \
>  		drm_simple_kms_helper.o drm_modeset_helper.o \
>  		drm_scdc_helper.o
>  
> +drm_kms_helper-$(CONFIG_DRM_DP_CEC) += drm_dp_cec.o
>  drm_kms_helper-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
>  drm_kms_helper-$(CONFIG_DRM_KMS_CMA_HELPER) += drm_fb_cma_helper.o
> diff --git a/drivers/gpu/drm/drm_dp_cec.c b/drivers/gpu/drm/drm_dp_cec.c
> new file mode 100644
> index 000000000000..44c544ba53cb
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_dp_cec.c
> @@ -0,0 +1,196 @@
> +/*
> + * DisplayPort CEC-Tunneling-over-AUX support
> + *
> + * Copyright 2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
> + *
> + * This program is free software; you may redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; version 2 of the License.
> + *
> + * 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 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/kernel.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <drm/drm_dp_helper.h>
> +#include <media/cec.h>
> +
> +static int drm_dp_cec_adap_enable(struct cec_adapter *adap, bool enable)
> +{
> +	struct drm_dp_aux *aux = cec_get_drvdata(adap);
> +	ssize_t err = 0;
> +
> +	if (enable)
> +		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL,
> +					 DP_CEC_TUNNELING_ENABLE);
> +	else
> +		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, 0);
> +	return (enable && err < 0) ? err : 0;
> +}
> +
> +static int drm_dp_cec_adap_log_addr(struct cec_adapter *adap, u8 addr)
> +{
> +	struct drm_dp_aux *aux = cec_get_drvdata(adap);
> +	u8 mask[2] = { 0x00, 0x80 };
> +	ssize_t err;
> +
> +	if (addr != CEC_LOG_ADDR_INVALID) {
> +		u16 la_mask = adap->log_addrs.log_addr_mask;
> +
> +		la_mask |= 0x8000 | (1 << addr);
> +		mask[0] = la_mask & 0xff;
> +		mask[1] = la_mask >> 8;
> +	}
> +	err = drm_dp_dpcd_write(aux, DP_CEC_LOGICAL_ADDRESS_MASK, mask, 2);
> +	return (addr != CEC_LOG_ADDR_INVALID && err < 0) ? err : 0;
> +}
> +
> +static int drm_dp_cec_adap_transmit(struct cec_adapter *adap, u8 attempts,
> +				    u32 signal_free_time, struct cec_msg *msg)
> +{
> +	struct drm_dp_aux *aux = cec_get_drvdata(adap);
> +	unsigned int retries = attempts - 1;
> +	ssize_t err;
> +
> +	err = drm_dp_dpcd_write(aux, DP_CEC_TX_MESSAGE_BUFFER,
> +				msg->msg, msg->len);
> +	if (err < 0)
> +		return err;
> +
> +	if (retries > 5)
> +		retries = 5;
> +	err = drm_dp_dpcd_writeb(aux, DP_CEC_TX_MESSAGE_INFO,
> +				 (msg->len - 1) | (retries << 4) |
> +				 DP_CEC_TX_MESSAGE_SEND);
> +	return err < 0 ? err : 0;
> +}
> +
> +static int drm_dp_cec_adap_monitor_all_enable(struct cec_adapter *adap,
> +					      bool enable)
> +{
> +	struct drm_dp_aux *aux = cec_get_drvdata(adap);
> +	ssize_t err;
> +	u8 val;
> +
> +	if (!(adap->capabilities & CEC_CAP_MONITOR_ALL))
> +		return 0;
> +
> +	err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CONTROL, &val);
> +	if (err >= 0) {
> +		if (enable)
> +			val |= DP_CEC_SNOOPING_ENABLE;
> +		else
> +			val &= ~DP_CEC_SNOOPING_ENABLE;
> +		err = drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_CONTROL, val);
> +	}
> +	return (enable && err < 0) ? err : 0;
> +}
> +
> +static const struct cec_adap_ops drm_dp_cec_adap_ops = {
> +	.adap_enable = drm_dp_cec_adap_enable,
> +	.adap_log_addr = drm_dp_cec_adap_log_addr,
> +	.adap_transmit = drm_dp_cec_adap_transmit,
> +	.adap_monitor_all_enable = drm_dp_cec_adap_monitor_all_enable,
> +};
> +
> +static int drm_dp_cec_received(struct drm_dp_aux *aux)
> +{
> +	struct cec_adapter *adap = aux->cec_adap;
> +	struct cec_msg msg;
> +	u8 rx_msg_info;
> +	ssize_t err;
> +
> +	err = drm_dp_dpcd_readb(aux, DP_CEC_RX_MESSAGE_INFO, &rx_msg_info);
> +	if (err < 0)
> +		return err;
> +	if (!(rx_msg_info & DP_CEC_RX_MESSAGE_ENDED))
> +		return 0;
> +	msg.len = (rx_msg_info & DP_CEC_RX_MESSAGE_LEN_MASK) + 1;
> +	err = drm_dp_dpcd_read(aux, DP_CEC_RX_MESSAGE_BUFFER, msg.msg, msg.len);
> +	if (err < 0)
> +		return err;
> +	cec_received_msg(adap, &msg);
> +	return 0;
> +}
> +
> +int drm_dp_cec_irq(struct drm_dp_aux *aux)
> +{
> +	struct cec_adapter *adap = aux->cec_adap;
> +	u8 flags;
> +	ssize_t err;
> +
> +	if (!aux->cec_adap)
> +		return 0;
> +
> +	err = drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, &flags);
> +	if (err < 0)
> +		return err;
> +
> +	if (flags & DP_CEC_RX_MESSAGE_INFO_VALID)
> +		drm_dp_cec_received(aux);
> +
> +	if (flags & DP_CEC_TX_MESSAGE_SENT)
> +		cec_transmit_done(adap, CEC_TX_STATUS_OK, 0, 0, 0, 0);
> +	else if (flags & DP_CEC_TX_LINE_ERROR)
> +		cec_transmit_done(adap, CEC_TX_STATUS_ERROR |
> +				  CEC_TX_STATUS_MAX_RETRIES, 0, 0, 0, 1);
> +	else if (flags &
> +		 (DP_CEC_TX_ADDRESS_NACK_ERROR | DP_CEC_TX_DATA_NACK_ERROR))
> +		cec_transmit_done(adap, CEC_TX_STATUS_NACK |
> +				  CEC_TX_STATUS_MAX_RETRIES, 0, 1, 0, 0);
> +	drm_dp_dpcd_writeb(aux, DP_CEC_TUNNELING_IRQ_FLAGS, flags);
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_cec_irq);
> +
> +int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux, const char *name,
> +				 struct device *parent)
> +{
> +	u32 cec_caps = CEC_CAP_LOG_ADDRS | CEC_CAP_TRANSMIT |
> +		       CEC_CAP_PASSTHROUGH | CEC_CAP_RC | CEC_CAP_NEEDS_HPD;
> +	unsigned int num_las = 1;
> +	int err;
> +	u8 cap;
> +
> +	if (drm_dp_dpcd_readb(aux, DP_CEC_TUNNELING_CAPABILITY, &cap) != 1 ||
> +	    !(cap & DP_CEC_TUNNELING_CAPABLE)) {
> +		cec_unregister_adapter(aux->cec_adap);
> +		aux->cec_adap = NULL;
> +		return -ENODEV;
> +	}
> +
> +	if (cap & DP_CEC_SNOOPING_CAPABLE)
> +		cec_caps |= CEC_CAP_MONITOR_ALL;
> +	if (cap & DP_CEC_MULTIPLE_LA_CAPABLE)
> +		num_las = CEC_MAX_LOG_ADDRS;
> +
> +	if (!IS_ERR_OR_NULL(aux->cec_adap)) {
> +		if (aux->cec_adap->capabilities == cec_caps &&
> +		    aux->cec_adap->available_log_addrs == num_las)
> +			return 0;
> +		cec_unregister_adapter(aux->cec_adap);
> +	}
> +
> +	aux->cec_adap = cec_allocate_adapter(&drm_dp_cec_adap_ops,
> +			 aux, name, cec_caps, num_las);
> +	if (IS_ERR(aux->cec_adap)) {
> +		err = PTR_ERR(aux->cec_adap);
> +		aux->cec_adap = NULL;
> +		return err;
> +	}
> +	err = cec_register_adapter(aux->cec_adap, parent);
> +	if (err) {
> +		cec_delete_adapter(aux->cec_adap);
> +		aux->cec_adap = NULL;
> +	}
> +	return err;
> +}
> +EXPORT_SYMBOL(drm_dp_cec_configure_adapter);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 3f4ad709534e..1e373df48108 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -843,6 +843,8 @@ struct drm_dp_aux_msg {
>  	size_t size;
>  };
>  
> +struct cec_adapter;
> +
>  /**
>   * struct drm_dp_aux - DisplayPort AUX channel
>   * @name: user-visible name of this AUX channel and the I2C-over-AUX adapter
> @@ -901,6 +903,10 @@ struct drm_dp_aux {
>  	 * @i2c_defer_count: Counts I2C DEFERs, used for DP validation.
>  	 */
>  	unsigned i2c_defer_count;
> +	/**
> +	 * @cec_adap: the CEC adapter for CEC-Tunneling-over-AUX support.
> +	 */
> +	struct cec_adapter *cec_adap;
>  };
>  
>  ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset,
> @@ -972,4 +978,22 @@ void drm_dp_aux_unregister(struct drm_dp_aux *aux);
>  int drm_dp_start_crc(struct drm_dp_aux *aux, struct drm_crtc *crtc);
>  int drm_dp_stop_crc(struct drm_dp_aux *aux);
>  
> +#ifdef CONFIG_DRM_DP_CEC
> +int drm_dp_cec_irq(struct drm_dp_aux *aux);
> +int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux, const char *name,
> +				 struct device *parent);
> +#else
> +static inline int drm_dp_cec_irq(struct drm_dp_aux *aux)
> +{
> +	return 0;
> +}
> +
> +static inline int drm_dp_cec_configure_adapter(struct drm_dp_aux *aux,
> +					       const char *name,
> +					       struct device *parent)
> +{
> +	return -ENODEV;
> +}
> +#endif
> +
>  #endif /* _DRM_DP_HELPER_H_ */
> -- 
> 2.11.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch



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