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... > > Tested-by: bo.b.wang at intel.com > 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 | 39 ++++++++++++++++++++++--------------- > 1 file changed, 23 insertions(+), 16 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c > index d85ebb0..f0a1a6f 100644 > --- a/drivers/gpu/drm/i915/intel_sdvo.c > +++ b/drivers/gpu/drm/i915/intel_sdvo.c > @@ -522,19 +522,32 @@ 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. > */ > if (!intel_sdvo_read_byte(intel_sdvo, > SDVO_I2C_CMD_STATUS, > &status)) > goto log_fail; > > - while (status == SDVO_CMD_STATUS_PENDING && retry--) { > - udelay(15); > - if (!intel_sdvo_read_byte(intel_sdvo, > - SDVO_I2C_CMD_STATUS, > - &status)) > - goto log_fail; > - } > + do { > + int quick = 5; > + > + while (status == SDVO_CMD_STATUS_PENDING && quick--) { > + udelay(15); > + if (!intel_sdvo_read_byte(intel_sdvo, > + SDVO_I2C_CMD_STATUS, > + &status)) > + goto log_fail; > + } > + > + if (status != SDVO_CMD_STATUS_PENDING || --retry == 0) > + break; > + > + msleep(15); > + } while (1); Is your intention to have 5 quick retries nested in 5 slow retries, resulting in 25 retries total? What do the quick retries buy you after the first msleep(15)? In other words, why not just do something simple like: diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c index 30f1752..3b2eddc 100644 --- a/drivers/gpu/drm/i915/intel_sdvo.c +++ b/drivers/gpu/drm/i915/intel_sdvo.c @@ -504,7 +504,7 @@ out: static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo, void *response, int response_len) { - u8 retry = 5; + u8 retry = 2*5; u8 status; int i; @@ -524,7 +524,10 @@ static bool intel_sdvo_read_response(struct intel_sdvo *intel_sdvo, goto log_fail; while (status == SDVO_CMD_STATUS_PENDING && retry--) { - udelay(15); + if (retry >= 5) + udelay(15); + else + msleep(15); if (!intel_sdvo_read_byte(intel_sdvo, SDVO_I2C_CMD_STATUS, &status)) BR, Jani. > > if (status <= SDVO_CMD_STATUS_SCALING_NOT_SUPP) > DRM_LOG_KMS("(%s)", cmd_status_names[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
