On Wed, 14 Dec 2022, Arun R Murthy <arun.r.murthy@xxxxxxxxx> wrote:
> The busy timeout logic checks for the AUX BUSY, then waits for the
> timeout period and then after timeout reads the register for BUSY or
> Success.
> Instead replace interrupt with polling so as to read the AUX CTL
> register often before the timeout period. Looks like there might be some
> issue with interrupt-on-read. Hence changing the logic to polling read.
>
> v2: replace interrupt with polling read
> v3: use usleep_rang instead of msleep, updated commit msg
> v4: use intel_wait_for_regiter internal function
> v5: use __intel_de_wait_for_register with 500us slow and 10ms fast timeout
>
> Signed-off-by: Arun R Murthy <arun.r.murthy@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/intel_dp_aux.c | 35 ++++++---------------
> 1 file changed, 9 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> index 91c93c93e5fc..772da38b451f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> @@ -34,31 +34,6 @@ static void intel_dp_aux_unpack(u32 src, u8 *dst, int dst_bytes)
> dst[i] = src >> ((3 - i) * 8);
> }
>
> -static u32
> -intel_dp_aux_wait_done(struct intel_dp *intel_dp)
> -{
> - struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> - i915_reg_t ch_ctl = intel_dp->aux_ch_ctl_reg(intel_dp);
> - const unsigned int timeout_ms = 10;
> - u32 status;
> - bool done;
> -
> -#define C (((status = intel_de_read_notrace(i915, ch_ctl)) & DP_AUX_CH_CTL_SEND_BUSY) == 0)
> - done = wait_event_timeout(i915->display.gmbus.wait_queue, C,
> - msecs_to_jiffies_timeout(timeout_ms));
> -
> - /* just trace the final value */
> - trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
> -
> - if (!done)
> - drm_err(&i915->drm,
> - "%s: did not complete or timeout within %ums (status 0x%08x)\n",
> - intel_dp->aux.name, timeout_ms, status);
> -#undef C
> -
> - return status;
> -}
> -
Please keep the function.
intel_dp_aux_xfer() is long enough as it is. It really doesn't need the
added lines, quite the opposite.
The intel_dp_aux_wait_done() also gives a name to what's being done.
> static u32 g4x_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
> {
> struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> @@ -264,6 +239,7 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> }
>
> while ((aux_clock_divider = intel_dp->get_aux_clock_divider(intel_dp, clock++))) {
> + u32 timeout_ms = 10;
> u32 send_ctl = intel_dp->get_aux_send_ctl(intel_dp,
> send_bytes,
> aux_clock_divider);
> @@ -281,7 +257,14 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> /* Send the command and wait for it to complete */
> intel_de_write(i915, ch_ctl, send_ctl);
>
> - status = intel_dp_aux_wait_done(intel_dp);
> + __intel_de_wait_for_register(i915, ch_ctl,
> + DP_AUX_CH_CTL_SEND_BUSY, 0,
> + 500, timeout_ms, &status);
> +
> + if ((status & DP_AUX_CH_CTL_SEND_BUSY) != 0)
> + drm_err(&i915->drm,
> + "%s: did not complete or timeout within %ums (status 0x%08x)\n",
> + intel_dp->aux.name, timeout_ms, status);
Please use the return value of intel_de_wait_for_register() to determine
the timeout instead of duplicating the condition. (Feels like I said
this a few times already?)
BR,
Jani.
>
> /* Clear done status and any errors */
> intel_de_write(i915, ch_ctl,
--
Jani Nikula, Intel Open Source Graphics Center
