Re: [Intel-gfx] [PATCH 2/2] drm/i915: Get rid of intel_dp_dpcd_read_wake()

From: Ville Syrjälä
Date: Fri Mar 18 2016 - 12:12:44 EST

On Fri, Mar 18, 2016 at 04:13:45PM +0200, Ville Syrjälä wrote:
> On Thu, Mar 17, 2016 at 11:40:45AM -0400, Lyude wrote:
> > Since we've fixed up drm_dp_dpcd_read() to allow for retries when things
> > timeout, there's no use for having this function anymore. Good riddens.
> >
> > Signed-off-by: Lyude <cpaul@xxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 79 ++++++++++++-----------------------------
> > 1 file changed, 22 insertions(+), 57 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index cdc2c15..fb4cbbe5 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -3190,47 +3190,14 @@ static void chv_dp_post_pll_disable(struct intel_encoder *encoder)
> > }
> >
> > /*
> > - * Native read with retry for link status and receiver capability reads for
> > - * cases where the sink may still be asleep.
> > - *
> > - * Sinks are *supposed* to come up within 1ms from an off state, but we're also
> > - * supposed to retry 3 times per the spec.
> > - */
> > -static ssize_t
> > -intel_dp_dpcd_read_wake(struct drm_dp_aux *aux, unsigned int offset,
> > - void *buffer, size_t size)
> > -{
> > - ssize_t ret;
> > - int i;
> > -
> > - /*
> > - * Sometime we just get the same incorrect byte repeated
> > - * over the entire buffer. Doing just one throw away read
> > - * initially seems to "solve" it.
> > - */
> > - drm_dp_dpcd_read(aux, DP_DPCD_REV, buffer, 1);
>
> NAK
>
> If people keep intentionally breaking my shit I'm going to become
> really grumpy soon.

Oh, and just in case someone wants to come up with a better kludge,
I just spent a few minutes analyzing the behavior of this crappy
monitor a.

What happens is that when the monitor is fully powered up (LED is blue)
things are fine. After the monitor goes to sleep (LED turns orange)
the first DPCD read will produce garbage. Further DPCD reads are fine,
even if I wait a significant amount of time between the reads, as long
as the monitor didn't do a power on->off cycle in between. So it looks
like it's always just the first read after power down that gets
corrupted.

Now I think I'll go and test how writes behave, assuming I can find a
decently sized chunk of DPCD address space I can write. And maybe I
should also try i2c-over-aux...

>
> > -
> > - for (i = 0; i < 3; i++) {
> > - ret = drm_dp_dpcd_read(aux, offset, buffer, size);
> > - if (ret == size)
> > - return ret;
> > - msleep(1);
> > - }
> > -
> > - return ret;
> > -}
> > -
> > -/*
> > * Fetch AUX CH registers 0x202 - 0x207 which contain
> > * link status information
> > */
> > bool
> > intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t link_status[DP_LINK_STATUS_SIZE])
> > {
> > - return intel_dp_dpcd_read_wake(&intel_dp->aux,
> > - DP_LANE0_1_STATUS,
> > - link_status,
> > - DP_LINK_STATUS_SIZE) == DP_LINK_STATUS_SIZE;
> > + return drm_dp_dpcd_read(&intel_dp->aux, DP_LANE0_1_STATUS, link_status,
> > + DP_LINK_STATUS_SIZE) == DP_LINK_STATUS_SIZE;
> > }
> >
> > /* These are source-specific values. */
> > @@ -3865,8 +3832,8 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > struct drm_i915_private *dev_priv = dev->dev_private;
> > uint8_t rev;
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, 0x000, intel_dp->dpcd,
> > - sizeof(intel_dp->dpcd)) < 0)
> > + if (drm_dp_dpcd_read(&intel_dp->aux, 0x000, intel_dp->dpcd,
> > + sizeof(intel_dp->dpcd)) < 0)
> > return false; /* aux transfer failed */
> >
> > DRM_DEBUG_KMS("DPCD: %*ph\n", (int) sizeof(intel_dp->dpcd), intel_dp->dpcd);
> > @@ -3877,9 +3844,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > /* Check if the panel supports PSR */
> > memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
> > if (is_edp(intel_dp)) {
> > - intel_dp_dpcd_read_wake(&intel_dp->aux, DP_PSR_SUPPORT,
> > - intel_dp->psr_dpcd,
> > - sizeof(intel_dp->psr_dpcd));
> > + drm_dp_dpcd_read(&intel_dp->aux, DP_PSR_SUPPORT,
> > + intel_dp->psr_dpcd,
> > + sizeof(intel_dp->psr_dpcd));
> > if (intel_dp->psr_dpcd[0] & DP_PSR_IS_SUPPORTED) {
> > dev_priv->psr.sink_support = true;
> > DRM_DEBUG_KMS("Detected EDP PSR Panel.\n");
> > @@ -3890,9 +3857,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > uint8_t frame_sync_cap;
> >
> > dev_priv->psr.sink_support = true;
> > - intel_dp_dpcd_read_wake(&intel_dp->aux,
> > - DP_SINK_DEVICE_AUX_FRAME_SYNC_CAP,
> > - &frame_sync_cap, 1);
> > + drm_dp_dpcd_read(&intel_dp->aux,
> > + DP_SINK_DEVICE_AUX_FRAME_SYNC_CAP,
> > + &frame_sync_cap, 1);
> > dev_priv->psr.aux_frame_sync = frame_sync_cap ? true : false;
> > /* PSR2 needs frame sync as well */
> > dev_priv->psr.psr2_support = dev_priv->psr.aux_frame_sync;
> > @@ -3908,15 +3875,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > /* Intermediate frequency support */
> > if (is_edp(intel_dp) &&
> > (intel_dp->dpcd[DP_EDP_CONFIGURATION_CAP] & DP_DPCD_DISPLAY_CONTROL_CAPABLE) &&
> > - (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_EDP_DPCD_REV, &rev, 1) == 1) &&
> > + (drm_dp_dpcd_read(&intel_dp->aux, DP_EDP_DPCD_REV, &rev, 1) == 1) &&
> > (rev >= 0x03)) { /* eDp v1.4 or higher */
> > __le16 sink_rates[DP_MAX_SUPPORTED_RATES];
> > int i;
> >
> > - intel_dp_dpcd_read_wake(&intel_dp->aux,
> > - DP_SUPPORTED_LINK_RATES,
> > - sink_rates,
> > - sizeof(sink_rates));
> > + drm_dp_dpcd_read(&intel_dp->aux, DP_SUPPORTED_LINK_RATES,
> > + sink_rates, sizeof(sink_rates));
> >
> > for (i = 0; i < ARRAY_SIZE(sink_rates); i++) {
> > int val = le16_to_cpu(sink_rates[i]);
> > @@ -3939,9 +3904,9 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> > if (intel_dp->dpcd[DP_DPCD_REV] == 0x10)
> > return true; /* no per-port downstream info */
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_DOWNSTREAM_PORT_0,
> > - intel_dp->downstream_ports,
> > - DP_MAX_DOWNSTREAM_PORTS) < 0)
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_DOWNSTREAM_PORT_0,
> > + intel_dp->downstream_ports,
> > + DP_MAX_DOWNSTREAM_PORTS) < 0)
> > return false; /* downstream port status fetch failed */
> >
> > return true;
> > @@ -3955,11 +3920,11 @@ intel_dp_probe_oui(struct intel_dp *intel_dp)
> > if (!(intel_dp->dpcd[DP_DOWN_STREAM_PORT_COUNT] & DP_OUI_SUPPORT))
> > return;
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_OUI, buf, 3) == 3)
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_OUI, buf, 3) == 3)
> > DRM_DEBUG_KMS("Sink OUI: %02hx%02hx%02hx\n",
> > buf[0], buf[1], buf[2]);
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_BRANCH_OUI, buf, 3) == 3)
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_BRANCH_OUI, buf, 3) == 3)
> > DRM_DEBUG_KMS("Branch OUI: %02hx%02hx%02hx\n",
> > buf[0], buf[1], buf[2]);
> > }
> > @@ -3975,7 +3940,7 @@ intel_dp_probe_mst(struct intel_dp *intel_dp)
> > if (intel_dp->dpcd[DP_DPCD_REV] < 0x12)
> > return false;
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_MSTM_CAP, buf, 1)) {
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_MSTM_CAP, buf, 1)) {
> > if (buf[0] & DP_MST_CAP) {
> > DRM_DEBUG_KMS("Sink is MST capable\n");
> > intel_dp->is_mst = true;
> > @@ -4112,7 +4077,7 @@ stop:
> > static bool
> > intel_dp_get_sink_irq(struct intel_dp *intel_dp, u8 *sink_irq_vector)
> > {
> > - return intel_dp_dpcd_read_wake(&intel_dp->aux,
> > + return drm_dp_dpcd_read(&intel_dp->aux,
> > DP_DEVICE_SERVICE_IRQ_VECTOR,
> > sink_irq_vector, 1) == 1;
> > }
> > @@ -4122,7 +4087,7 @@ intel_dp_get_sink_irq_esi(struct intel_dp *intel_dp, u8 *sink_irq_vector)
> > {
> > int ret;
> >
> > - ret = intel_dp_dpcd_read_wake(&intel_dp->aux,
> > + ret = drm_dp_dpcd_read(&intel_dp->aux,
> > DP_SINK_COUNT_ESI,
> > sink_irq_vector, 14);
> > if (ret != 14)
> > @@ -4383,7 +4348,7 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
> > intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
> > uint8_t reg;
> >
> > - if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
> > + if (drm_dp_dpcd_read(&intel_dp->aux, DP_SINK_COUNT,
> > &reg, 1) < 0)
> > return connector_status_unknown;
> >
> > --
> > 2.5.0
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Ville Syrjälä
> Intel OTC
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

--
Ville Syrjälä
Intel OTC