On Tue, 17 Dec 2013, Thierry Reding <thierry.reding@xxxxxxxxx> wrote: > This is a superset of the current i2c_dp_aux bus functionality and can > be used to transfer native AUX in addition to I2C-over-AUX messages. > > Helpers are provided to read and write the DPCD, either blockwise or > byte-wise. Many of the existing helpers for DisplayPort take a copy of a > portion of the DPCD and operate on that, without a way to write data > back to the DPCD (e.g. for configuration of the link). > > Subsequent patches will build upon this infrastructure to provide common > functionality in a generic way. > > Signed-off-by: Thierry Reding <treding@xxxxxxxxxx> > --- > drivers/gpu/drm/drm_dp_helper.c | 116 ++++++++++++++++++++++++++++++++++++++++ > include/drm/drm_dp_helper.h | 64 ++++++++++++++++++++++ > 2 files changed, 180 insertions(+) > > diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c > index 9e978aae8972..bd622d462ca7 100644 > --- a/drivers/gpu/drm/drm_dp_helper.c > +++ b/drivers/gpu/drm/drm_dp_helper.c > @@ -346,3 +346,119 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw) > } > } > EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate); > + > +/** > + * drm_dp_dpcd_read() - read a series of bytes from the DPCD > + * @aux: DisplayPort AUX channel > + * @offset: address of the (first) register to read > + * @buffer: buffer to store the register values > + * @size: number of bytes in @buffer > + * > + * Returns the number of bytes transferred on success, or a negative error > + * code on failure. > + */ > +ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, > + void *buffer, size_t size) > +{ > + struct drm_dp_aux_msg msg; > + unsigned int retry; > + int err; > + > + memset(&msg, 0, sizeof(msg)); > + msg.address = offset; > + msg.request = DP_AUX_NATIVE_READ; > + msg.buffer = buffer; > + msg.size = size; > + > + /* > + * The specification doesn't give any recommendation on how often to > + * retry native transactions, so retry 7 times like for I2C-over-AUX > + * transactions. > + */ > + for (retry = 0; retry < 7; retry++) { > + err = aux->transfer(aux, &msg); > + if (err < 0) { > + if (err == -EBUSY) > + continue; > + > + return err; > + } > + > + if (err == 0) > + return -EPROTO; > + > + switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { > + case DP_AUX_NATIVE_REPLY_ACK: > + return err; > + > + case DP_AUX_NATIVE_REPLY_NACK: > + return -EIO; > + > + case DP_AUX_NATIVE_REPLY_DEFER: > + usleep_range(400, 500); > + break; > + } > + } > + > + DRM_ERROR("too many retries, giving up\n"); > + return -EIO; > +} > +EXPORT_SYMBOL(drm_dp_dpcd_read); > + > +/** > + * drm_dp_dpcd_write() - write a series of bytes to the DPCD > + * @aux: DisplayPort AUX channel > + * @offset: address of the (first) register to write > + * @buffer: buffer containing the values to write > + * @size: number of bytes in @buffer > + * > + * Returns the number of bytes transferred on success, or a negative error > + * code on failure. > + */ > +ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset, > + void *buffer, size_t size) > +{ > + struct drm_dp_aux_msg msg; > + unsigned int retry; > + int err; > + > + memset(&msg, 0, sizeof(msg)); > + msg.address = offset; > + msg.request = DP_AUX_NATIVE_WRITE; > + msg.buffer = buffer; > + msg.size = size; > + > + /* > + * The specification doesn't give any recommendation on how often to > + * retry native transactions, so retry 7 times like for I2C-over-AUX > + * transactions. > + */ > + for (retry = 0; retry < 7; retry++) { > + err = aux->transfer(aux, &msg); > + if (err < 0) { > + if (err == -EBUSY) > + continue; > + > + return err; > + } > + > + if (err == 0) > + return -EPROTO; > + > + switch (msg.reply & DP_AUX_NATIVE_REPLY_MASK) { > + case DP_AUX_NATIVE_REPLY_ACK: > + return 0; "Returns the number of bytes transferred on success, or a negative error code on failure." Compare drm_dp_dpcd_read. You could add an internal helper to do both read and write, it's mostly the same code. BR, Jani. > + > + case DP_AUX_NATIVE_REPLY_NACK: > + return -EIO; > + > + case DP_AUX_NATIVE_REPLY_DEFER: > + usleep_range(400, 500); > + break; > + } > + } > + > + DRM_ERROR("too many retries, giving up\n"); > + return -EIO; > +} > +EXPORT_SYMBOL(drm_dp_dpcd_write); > diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h > index c873f9ce5871..0b14e799cd98 100644 > --- a/include/drm/drm_dp_helper.h > +++ b/include/drm/drm_dp_helper.h > @@ -397,4 +397,68 @@ drm_dp_enhanced_frame_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) > (dpcd[DP_MAX_LANE_COUNT] & DP_ENHANCED_FRAME_CAP); > } > > +/* > + * DisplayPort AUX channel > + */ > + > +/** > + * struct drm_dp_aux_msg - DisplayPort AUX channel transaction > + * @address: address of the (first) register to access > + * @flags: contains the type of transaction as well as flags (see above) > + * @reply: upon completion, contains the reply type of the transaction > + * @buffer: pointer to a transmission or reception buffer > + * @size: size of @buffer > + */ > +struct drm_dp_aux_msg { > + unsigned int address; > + u8 request; > + u8 reply; > + void *buffer; > + size_t size; > +}; > + > +/** > + * struct drm_dp_aux - DisplayPort AUX channel > + * @transfer: transfers a message representing a single AUX transaction > + */ > +struct drm_dp_aux { > + ssize_t (*transfer)(struct drm_dp_aux *aux, > + struct drm_dp_aux_msg *msg); > +}; > + > +ssize_t drm_dp_dpcd_read(struct drm_dp_aux *aux, unsigned int offset, > + void *buffer, size_t size); > +ssize_t drm_dp_dpcd_write(struct drm_dp_aux *aux, unsigned int offset, > + void *buffer, size_t size); > + > +/** > + * drm_dp_dpcd_readb() - read a single byte from the DPCD > + * @aux: DisplayPort AUX channel > + * @offset: address of the register to read > + * @valuep: location where the value of the register will be stored > + * > + * Returns the number of bytes transferred (1) on success, or a negative > + * error code on failure. > + */ > +static inline ssize_t drm_dp_dpcd_readb(struct drm_dp_aux *aux, > + unsigned int offset, u8 *valuep) > +{ > + return drm_dp_dpcd_read(aux, offset, valuep, 1); > +} > + > +/** > + * drm_dp_dpcd_writeb() - write a single byte to the DPCD > + * @aux: DisplayPort AUX channel > + * @offset: address of the register to write > + * @valuep: value to write to the register > + * > + * Returns the number of bytes transferred (1) on success, or a negative > + * error code on failure. > + */ > +static inline ssize_t drm_dp_dpcd_writeb(struct drm_dp_aux *aux, u8 value, > + unsigned int offset) > +{ > + return drm_dp_dpcd_write(aux, offset, &value, 1); > +} > + > #endif /* _DRM_DP_HELPER_H_ */ > -- > 1.8.4.2 > > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > http://lists.freedesktop.org/mailman/listinfo/dri-devel -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel