On Wed, 20 Nov 2024, Imre Deak <imre.deak@xxxxxxxxx> 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.
Ping. Okay to merge, or do we want to mull over the the timeout?
I'm primarily trying to do a non-functional change. I could omit the
timeout parameter, but for non-hubs three seconds seems excessive, and
reducing it for hubs too is a can of worms I prefer keeping the lid on
top.
> 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.
Honestly I think there's already enough of an acronym jumble in the
name. At least "drm_dp_dpcd" is common for most functions around here.
BR,
Jani.
>
>> +{
>> + int ret, status;
>> +
>
> Extra w/s.
>
> 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
>>
--
Jani Nikula, Intel
