On Fri, 23 Nov 2012 13:42:38 +0200, Jani Nikula <jani.nikula at linux.intel.com> wrote: > 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: Sure, looks better. -Chris -- Chris Wilson, Intel Open Source Technology Centre
