From mboxrd@z Thu Jan 1 00:00:00 1970 From: maxime.ripard@bootlin.com (Maxime Ripard) Date: Fri, 16 Feb 2018 16:50:49 +0100 Subject: [PATCH 2/2] drm/sun4i: Handle DRM_MODE_FLAG_**SYNC_POSITIVE correctly In-Reply-To: References: <1516474221-114596-1-git-send-email-giulio.benetti@micronovasrl.com> <1516474221-114596-2-git-send-email-giulio.benetti@micronovasrl.com> <20180122085112.7xo2t3x5ag4k2kpl@flea.lan> <59f7b542-3b1d-ff62-e290-37c47f4075ff@micronovasrl.com> <9929d894-53c3-a7e9-a328-a00cfc1ef546@micronovasrl.com> <20180207103905.mtyzgu73mmifyvvj@flea> <653f0438-c55a-02a5-dffb-2ee8e6d9ef4a@micronovasrl.com> <20180208204043.mqryuqhx7a6z4v3b@flea> Message-ID: <20180216155049.r2mc724nfluwrrbe@flea.lan> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Feb 15, 2018 at 07:05:56PM +0100, Giulio Benetti wrote: > > If so, and if remember the captures properly, the sampling would occur > > right before the rise, and not really around the fall. > > > > Would 2/3 be better here? > > Yes, you're right, 2/3 phase is better: > > 1/3 phase: https://pasteboard.co/H4VehON.png > 2/3 phase: https://pasteboard.co/H4Veq8a.png > > Take a look at the bit in middle(yellow) sampled by clock(blue). > > Rising edge is almost in the middle of D0 bit. > > > > > > According to scope captures above on both A20 and A33. > > > Unfortunately I don't have other boards for the other SoCs to take captures. > > > > > > What do you think? > > > > I guess we can make that part applicable to all SoCs, we haven't seen > > any significant differences on those part. > > So let's keep: > - As normal(rising edge) => IO_POL_REG "0x2 => 2/3 phase" > - As inverted(falling edge) => IO_POL_REG "0x0 => normal phase" I was actually thinking 1/3 for rising, 2/3 for falling. Maxime -- Maxime Ripard, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering http://bootlin.com -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 833 bytes Desc: not available URL: