On Fri, 23 Nov 2012, Chris Wilson <chris at chris-wilson.co.uk> wrote: > Some devices may respond very slowly and only flag that the reply is > pending within the first 15us response window. Be kind to such devices > and wait a further 15ms, before checking for the pending reply. This > moves the existing special case delay of 30ms down from the detection > routine into the common path and pretends to explain it... > > v2: Simplify the loop constructs as suggested by Jani Nikula. > > References: https://bugs.freedesktop.org/show_bug.cgi?id=36997 > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk> > --- > drivers/gpu/drm/i915/intel_sdvo.c | 31 +++++++++++++++++++------------ > 1 file changed, 19 insertions(+), 12 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c > index d85ebb0..cff3c0b 100644 > --- a/drivers/gpu/drm/i915/intel_sdvo.c > +++ b/drivers/gpu/drm/i915/intel_sdvo.c > @@ -509,7 +509,7 @@ out: > static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo, > void *response, int response_len) > { > - u8 retry = 5; > + u8 retry = 15; /* 5 quick checks, followed by 10 long checks */ > u8 status; > int i; > > @@ -522,14 +522,27 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo, > * command to be complete. > * > * Check 5 times in case the hardware failed to read the docs. > + * > + * Also beware that the first response by many devices is to > + * reply PENDING and stall for time. TVs are notorious for > + * requiring longer than specified to complete their replies. > + * Originally (in the DDX long ago), the delay was only ever 15ms > + * with an additional delay of 30ms applied for TVs added later after > + * many experiments. To accommodate both sets of delays, we do a > + * sequence of slow checks if the device is falling behind and fails > + * to reply within 5*15?s. > */ > if (!intel_sdvo_read_byte(intel_sdvo, > SDVO_I2C_CMD_STATUS, > &status)) > goto log_fail; > > - while (status == SDVO_CMD_STATUS_PENDING && retry--) { > - udelay(15); > + while (status == SDVO_CMD_STATUS_PENDING && --retry) { Hey, why did you switch from post to pre decrement? It will now retry only retry-1 times. Or is this about the semantics of retries vs. tries? ;) Otherwise, Reviewed-by: Jani Nikula <jani.nikula at intel.com> > + if (retry < 10) > + msleep(15); > + else > + udelay(15); > + > if (!intel_sdvo_read_byte(intel_sdvo, > SDVO_I2C_CMD_STATUS, > &status)) > @@ -1535,15 +1548,9 @@ intel_sdvo_detect(struct drm_connector *connector, bool force) > struct intel_sdvo_connector *intel_sdvo_connector = to_intel_sdvo_connector(connector); > enum drm_connector_status ret; > > - if (!intel_sdvo_write_cmd(intel_sdvo, > - SDVO_CMD_GET_ATTACHED_DISPLAYS, NULL, 0)) > - return connector_status_unknown; > - > - /* add 30ms delay when the output type might be TV */ > - if (intel_sdvo->caps.output_flags & SDVO_TV_MASK) > - msleep(30); > - > - if (!intel_sdvo_read_response(intel_sdvo, &response, 2)) > + if (!intel_sdvo_get_value(intel_sdvo, > + SDVO_CMD_GET_ATTACHED_DISPLAYS, > + &response, 2)) > return connector_status_unknown; > > DRM_DEBUG_KMS("SDVO response %d %d [%x]\n", > -- > 1.7.10.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx at lists.freedesktop.org > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
