On Wed, Nov 20, 2024 at 04:59:43PM +0200, Imre Deak wrote:
> On Mon, Nov 18, 2024 at 05:14:52PM +0200, Jani Nikula wrote:
> > SST with 128b/132b channel coding needs this too. Extract to a separate
> > helper, independent of MST.
> >
> > Pass timeout in as a parameter, anticipating that we can reduce the
> > timeout for SST.
>
> I wish there was a DP Standard section making the above clear,
> but I suppose we just deduct that except of the side-band messaging,
> every other payload programming and ACT signaling is required for
> 128b/132b SST.
>
> >
>
> Cc: Lyude Paul <lyude@xxxxxxxxxx>
>
> > Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/display/drm_dp_helper.c | 54 ++++++++++++++++++-
> > drivers/gpu/drm/display/drm_dp_mst_topology.c | 36 +------------
> > include/drm/display/drm_dp_helper.h | 2 +
> > 3 files changed, 57 insertions(+), 35 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c b/drivers/gpu/drm/display/drm_dp_helper.c
> > index 6ee51003de3c..b7e03bf02cd8 100644
> > --- a/drivers/gpu/drm/display/drm_dp_helper.c
> > +++ b/drivers/gpu/drm/display/drm_dp_helper.c
> > @@ -22,15 +22,16 @@
> >
> > #include <linux/backlight.h>
> > #include <linux/delay.h>
> > +#include <linux/dynamic_debug.h>
> > #include <linux/errno.h>
> > #include <linux/i2c.h>
> > #include <linux/init.h>
> > +#include <linux/iopoll.h>
> > #include <linux/kernel.h>
> > #include <linux/module.h>
> > #include <linux/sched.h>
> > #include <linux/seq_file.h>
> > #include <linux/string_helpers.h>
> > -#include <linux/dynamic_debug.h>
> >
> > #include <drm/display/drm_dp_helper.h>
> > #include <drm/display/drm_dp_mst_helper.h>
> > @@ -779,6 +780,57 @@ int drm_dp_dpcd_read_phy_link_status(struct drm_dp_aux *aux,
> > }
> > EXPORT_SYMBOL(drm_dp_dpcd_read_phy_link_status);
> >
> > +static int read_payload_update_status(struct drm_dp_aux *aux)
> > +{
> > + int ret;
> > + u8 status;
> > +
> > + ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
> > + if (ret < 0)
> > + return ret;
> > +
> > + return status;
> > +}
> > +
> > +/**
> > + * drm_dp_dpcd_poll_act_handled() - Polls for ACT handled status.
> > + * @aux: DisplayPort AUX channel
> > + * @timeout_ms: Timeout in ms
> > + *
> > + * Tries waiting for the sink to finish updating its payload table by polling
> > + * for the ACT handled bit for up to @timeout_ms milliseconds, defaulting to
> > + * 3000 ms if 0.
> > + *
> > + * Returns:
> > + * 0 if the ACT was handled in time, negative error code on failure.
> > + */
> > +int drm_dp_dpcd_poll_act_handled(struct drm_dp_aux *aux, int timeout_ms)
>
> I wonder if it'd make sense to namespace these helpers using ll_mtp or mtp.
>
> > +{
> > + int ret, status;
> > +
>
> Extra w/s.
Ah nvm, timeout_ms is a function param so new is needed.
>
> Regardless of the namespace comment:
>
> Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx>
>
> > + /* default to 3 seconds, this is arbitrary */
> > + timeout_ms = timeout_ms ?: 3000;
> > +
> > + ret = readx_poll_timeout(read_payload_update_status, aux, status,
> > + status & DP_PAYLOAD_ACT_HANDLED || status < 0,
> > + 200, timeout_ms * USEC_PER_MSEC);
> > + if (ret < 0 && status >= 0) {
> > + drm_err(aux->drm_dev, "Failed to get ACT after %d ms, last status: %02x\n",
> > + timeout_ms, status);
> > + return -EINVAL;
> > + } else if (status < 0) {
> > + /*
> > + * Failure here isn't unexpected - the hub may have
> > + * just been unplugged
> > + */
> > + drm_dbg_kms(aux->drm_dev, "Failed to read payload table status: %d\n", status);
> > + return status;
> > + }
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL(drm_dp_dpcd_poll_act_handled);
> > +
> > static bool is_edid_digital_input_dp(const struct drm_edid *drm_edid)
> > {
> > /* FIXME: get rid of drm_edid_raw() */
> > diff --git a/drivers/gpu/drm/display/drm_dp_mst_topology.c b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > index ac90118b9e7a..2bdbc1eb282b 100644
> > --- a/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > +++ b/drivers/gpu/drm/display/drm_dp_mst_topology.c
> > @@ -29,7 +29,6 @@
> > #include <linux/random.h>
> > #include <linux/sched.h>
> > #include <linux/seq_file.h>
> > -#include <linux/iopoll.h>
> >
> > #if IS_ENABLED(CONFIG_DRM_DEBUG_DP_MST_TOPOLOGY_REFS)
> > #include <linux/stacktrace.h>
> > @@ -4723,18 +4722,6 @@ static int drm_dp_dpcd_write_payload(struct drm_dp_mst_topology_mgr *mgr,
> > return ret;
> > }
> >
> > -static int do_get_act_status(struct drm_dp_aux *aux)
> > -{
> > - int ret;
> > - u8 status;
> > -
> > - ret = drm_dp_dpcd_readb(aux, DP_PAYLOAD_TABLE_UPDATE_STATUS, &status);
> > - if (ret < 0)
> > - return ret;
> > -
> > - return status;
> > -}
> > -
> > /**
> > * drm_dp_check_act_status() - Polls for ACT handled status.
> > * @mgr: manager to use
> > @@ -4752,28 +4739,9 @@ int drm_dp_check_act_status(struct drm_dp_mst_topology_mgr *mgr)
> > * There doesn't seem to be any recommended retry count or timeout in
> > * the MST specification. Since some hubs have been observed to take
> > * over 1 second to update their payload allocations under certain
> > - * conditions, we use a rather large timeout value.
> > + * conditions, we use a rather large timeout value of 3 seconds.
> > */
> > - const int timeout_ms = 3000;
> > - int ret, status;
> > -
> > - ret = readx_poll_timeout(do_get_act_status, mgr->aux, status,
> > - status & DP_PAYLOAD_ACT_HANDLED || status < 0,
> > - 200, timeout_ms * USEC_PER_MSEC);
> > - if (ret < 0 && status >= 0) {
> > - drm_err(mgr->dev, "Failed to get ACT after %dms, last status: %02x\n",
> > - timeout_ms, status);
> > - return -EINVAL;
> > - } else if (status < 0) {
> > - /*
> > - * Failure here isn't unexpected - the hub may have
> > - * just been unplugged
> > - */
> > - drm_dbg_kms(mgr->dev, "Failed to read payload table status: %d\n", status);
> > - return status;
> > - }
> > -
> > - return 0;
> > + return drm_dp_dpcd_poll_act_handled(mgr->aux, 3000);
> > }
> > EXPORT_SYMBOL(drm_dp_check_act_status);
> >
> > diff --git a/include/drm/display/drm_dp_helper.h b/include/drm/display/drm_dp_helper.h
> > index 279624833ea9..38eea21d1082 100644
> > --- a/include/drm/display/drm_dp_helper.h
> > +++ b/include/drm/display/drm_dp_helper.h
> > @@ -567,6 +567,8 @@ int drm_dp_dpcd_read_phy_link_status(struct drm_dp_aux *aux,
> > enum drm_dp_phy dp_phy,
> > u8 link_status[DP_LINK_STATUS_SIZE]);
> >
> > +int drm_dp_dpcd_poll_act_handled(struct drm_dp_aux *aux, int timeout_ms);
> > +
> > bool drm_dp_send_real_edid_checksum(struct drm_dp_aux *aux,
> > u8 real_edid_checksum);
> >
> > --
> > 2.39.5
> >
