On Mon, Nov 11, 2019 at 01:43:52AM +0000, allen.chen@xxxxxxxxxx wrote: > Hi Ville Syrjälä > > Thanks for your suggestion and I have replied two comments below. > > From: Ville Syrjälä [mailto:ville.syrjala@xxxxxxxxxxxxxxx] > Sent: Thursday, November 07, 2019 11:42 PM > To: Allen Chen (陳柏宇) > Cc: Jau-Chih Tseng (曾昭智); Maxime Ripard; open list; open list:DRM DRIVERS; David Airlie; Pi-Hsun Shih; Sean Paul > Subject: Re: [PATCH] drm/edid: fixup EDID 1.3 and 1.4 judge reduced-blanking timings logic > > On Mon, Nov 04, 2019 at 04:42:49PM +0800, allen wrote: > > According to VESA ENHANCED EXTENDED DISPLAY IDENTIFICATION DATA STANDARD > > (Defines EDID Structure Version 1, Revision 4) page: 39 > > How to determine whether the monitor support RB timing or not? > > EDID 1.4 > > First: read detailed timing descriptor and make sure byte0 = 0, > > byte1 = 0, byte2 = 0 and byte3 = 0xFD > > That should probably be some new function: > bool is_display_descriptor(const u8 *desc, u8 tag); > is_display_descriptor(EDID_DETAIL_MONITOR_RANGE) > or something along those lines > > We don't seem to check that in most places so should be rolled out all > over. The usage of struct detailed_timing all over also makes everything > rather confusing. > > > Second: read detailed timing descriptor byte10 = 0x04 and > > EDID byte18h bit0 = 1 > > Indicates CVT support. Should give these things real names so > one wouldn't have to decode by hand. > > > Third: if EDID byte18h bit0 == 1 && byte10 == 0x04, > > then we can check byte15, if byte15 bit4 =1 is support RB > > if EDID byte18h bit0 != 1 || byte10 != 0x04, > > then byte15 can not be used > > > > The linux code is_rb function not follow the VESA's rule > > > > EDID 1.3 > > LCD flat panels do not require long blanking intervals as a retrace > > period so default support reduced-blanking timings. > > > > Signed-off-by: Allen Chen <allen.chen@xxxxxxxxxx> > > Reported-by: kbuild test robot <lkp@xxxxxxxxx> > > --- > > drivers/gpu/drm/drm_edid.c | 28 +++++++++++++++++++++------- > > 1 file changed, 21 insertions(+), 7 deletions(-) > > > > diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c > > index e5e7e65..9b67b80 100644 > > --- a/drivers/gpu/drm/drm_edid.c > > +++ b/drivers/gpu/drm/drm_edid.c > > @@ -93,6 +93,11 @@ struct detailed_mode_closure { > > int modes; > > }; > > > > +struct edid_support_rb_closure { > > + struct edid *edid; > > + s8 support_rb; > > bool > > ==> ITE: If use bool, we could not return EDID1.3 when EDID1.4 logic can not be applied Hmm. Could use two bools then. > > +}; > > + > > #define LEVEL_DMT 0 > > #define LEVEL_GTF 1 > > #define LEVEL_GTF2 2 > > @@ -2018,22 +2023,31 @@ struct drm_display_mode *drm_mode_find_dmt(struct drm_device *dev, > > is_rb(struct detailed_timing *t, void *data) > > { > > u8 *r = (u8 *)t; > > - if (r[3] == EDID_DETAIL_MONITOR_RANGE) > > - if (r[15] & 0x10) > > - *(bool *)data = true; > > + struct edid_support_rb_closure *closure = data; > > + struct edid *edid = closure->edid; > > + > > + if (!r[0] && !r[1] && !r[2] && r[3] == EDID_DETAIL_MONITOR_RANGE) { > > + if (edid->features & BIT(0) && r[10] == BIT(2)) > > + closure->support_rb = (r[15] & 0x10) ? 1 : 0; > > With the bool the ternary operator is not needed. Also should maybe > be |= in case we have multiple range descriptors? Not sure that is > legal. > > > + } > > } > > > > /* EDID 1.4 defines this explicitly. For EDID 1.3, we guess, badly. */ > > static bool > > drm_monitor_supports_rb(struct edid *edid) > > { > > + struct edid_support_rb_closure closure = { > > + .edid = edid, > > + .support_rb = -1, > > + }; > > + > > if (edid->revision >= 4) { > > - bool ret = false; > > - drm_for_each_detailed_block((u8 *)edid, is_rb, &ret); > > - return ret; > > + drm_for_each_detailed_block((u8 *)edid, is_rb, &closure); > > + if (closure.support_rb >= 0) > > + return closure.support_rb; > > } > > > > - return ((edid->input & DRM_EDID_INPUT_DIGITAL) != 0); > > + return true; > > Why are we now assuming rb for all pre 1.4 EDIDs? > > ==> ITE: Today, most of the monitor are LCD and LCD monitor do not require long blanking intervals as a retrace period so default support reduced-blanking timings. You can't assume such things. Someone out there is surely still using something that doesn't do reduced blanking. > > > } > > > > static void > > -- > > 1.9.1 > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > https://lists.freedesktop.org/mailman/listinfo/dri-devel > > -- > Ville Syrjälä > Intel -- Ville Syrjälä Intel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
