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Teki Subject: Re: [PATCH v10 01/11] drm/sun4i: dsi: Fix TCON DRQ set bits Message-ID: <20190614144526.lorg3saj4wjopgne@flea> References: <20190520090318.27570-1-jagan@amarulasolutions.com> <20190520090318.27570-2-jagan@amarulasolutions.com> <20190523203407.o5obg2wtj7wwau6a@flea> <20190529145450.qnitxpmpr2a2xemk@flea> <20190604100011.cqkhpwmmmwh3vr3y@flea> <20190613125630.2b2fvvtvrcjlx4lv@flea> MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20180716 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190614_074533_590489_CAF87BA1 X-CRM114-Status: GOOD ( 26.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Bhushan Shah , David Airlie , linux-sunxi , linux-kernel , dri-devel , =?utf-8?B?5Z2a5a6a5YmN6KGM?= , Chen-Yu Tsai , Daniel Vetter , Michael Trimarchi , linux-amarula , linux-arm-kernel Content-Type: multipart/mixed; boundary="===============0847348986080960914==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============0847348986080960914== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="a2qaubfige6iysy4" Content-Disposition: inline --a2qaubfige6iysy4 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Fri, Jun 14, 2019 at 12:03:13PM +0530, Jagan Teki wrote: > On Thu, Jun 13, 2019 at 6:56 PM Maxime Ripard wrote: > > > > On Wed, Jun 05, 2019 at 01:17:11PM +0530, Jagan Teki wrote: > > > On Tue, Jun 4, 2019 at 3:30 PM Maxime Ripard wrote: > > > > > > > > On Wed, May 29, 2019 at 11:44:56PM +0530, Jagan Teki wrote: > > > > > On Wed, May 29, 2019 at 8:24 PM Maxime Ripard wrote: > > > > > > > > > > > > On Fri, May 24, 2019 at 03:48:51PM +0530, Jagan Teki wrote: > > > > > > > On Fri, May 24, 2019 at 2:04 AM Maxime Ripard wrote: > > > > > > > > > > > > > > > > On Mon, May 20, 2019 at 02:33:08PM +0530, Jagan Teki wrote: > > > > > > > > > According to "DRM kernel-internal display mode structure" in > > > > > > > > > include/drm/drm_modes.h the current driver is trying to include > > > > > > > > > sync timings along with front porch value while checking and > > > > > > > > > computing drq set bits in non-burst mode. > > > > > > > > > > > > > > > > > > mode->hsync_end - mode->hdisplay => horizontal front porch + sync > > > > > > > > > > > > > > > > > > With adding additional sync timings, the dsi controller leads to > > > > > > > > > wrong drq set bits for "bananapi,s070wv20-ct16" panel which indeed > > > > > > > > > trigger panel flip_done timed out as: > > > > > > > > > > > > > > > > > > WARNING: CPU: 0 PID: 31 at drivers/gpu/drm/drm_atomic_helper.c:1429 drm_atomic_helper_wait_for_vblanks.part.1+0x298/0x2a0 > > > > > > > > > [CRTC:46:crtc-0] vblank wait timed out > > > > > > > > > Modules linked in: > > > > > > > > > CPU: 0 PID: 31 Comm: kworker/0:1 Not tainted 5.1.0-next-20190514-00026-g01f0c75b902d-dirty #13 > > > > > > > > > Hardware name: Allwinner sun8i Family > > > > > > > > > Workqueue: events deferred_probe_work_func > > > > > > > > > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > > > > > > > > > [] (show_stack) from [] (dump_stack+0x84/0x98) > > > > > > > > > [] (dump_stack) from [] (__warn+0xfc/0x114) > > > > > > > > > [] (__warn) from [] (warn_slowpath_fmt+0x44/0x68) > > > > > > > > > [] (warn_slowpath_fmt) from [] (drm_atomic_helper_wait_for_vblanks.part.1+0x298/0x2a0) > > > > > > > > > [] (drm_atomic_helper_wait_for_vblanks.part.1) from [] (drm_atomic_helper_commit_tail_rpm+0x5c/0x6c) > > > > > > > > > [] (drm_atomic_helper_commit_tail_rpm) from [] (commit_tail+0x40/0x6c) > > > > > > > > > [] (commit_tail) from [] (drm_atomic_helper_commit+0xbc/0x128) > > > > > > > > > [] (drm_atomic_helper_commit) from [] (restore_fbdev_mode_atomic+0x1cc/0x1dc) > > > > > > > > > [] (restore_fbdev_mode_atomic) from [] (drm_fb_helper_restore_fbdev_mode_unlocked+0x54/0xa0) > > > > > > > > > [] (drm_fb_helper_restore_fbdev_mode_unlocked) from [] (drm_fb_helper_set_par+0x30/0x54) > > > > > > > > > [] (drm_fb_helper_set_par) from [] (fbcon_init+0x560/0x5ac) > > > > > > > > > [] (fbcon_init) from [] (visual_init+0xbc/0x104) > > > > > > > > > [] (visual_init) from [] (do_bind_con_driver+0x1b0/0x390) > > > > > > > > > [] (do_bind_con_driver) from [] (do_take_over_console+0x13c/0x1c4) > > > > > > > > > [] (do_take_over_console) from [] (do_fbcon_takeover+0x74/0xcc) > > > > > > > > > [] (do_fbcon_takeover) from [] (notifier_call_chain+0x44/0x84) > > > > > > > > > [] (notifier_call_chain) from [] (__blocking_notifier_call_chain+0x48/0x60) > > > > > > > > > [] (__blocking_notifier_call_chain) from [] (blocking_notifier_call_chain+0x18/0x20) > > > > > > > > > [] (blocking_notifier_call_chain) from [] (register_framebuffer+0x1e0/0x2f8) > > > > > > > > > [] (register_framebuffer) from [] (__drm_fb_helper_initial_config_and_unlock+0x2fc/0x50c) > > > > > > > > > [] (__drm_fb_helper_initial_config_and_unlock) from [] (drm_fbdev_client_hotplug+0xe8/0x1b8) > > > > > > > > > [] (drm_fbdev_client_hotplug) from [] (drm_fbdev_generic_setup+0x88/0x118) > > > > > > > > > [] (drm_fbdev_generic_setup) from [] (sun4i_drv_bind+0x128/0x160) > > > > > > > > > [] (sun4i_drv_bind) from [] (try_to_bring_up_master+0x164/0x1a0) > > > > > > > > > [] (try_to_bring_up_master) from [] (__component_add+0x94/0x140) > > > > > > > > > [] (__component_add) from [] (sun6i_dsi_probe+0x144/0x234) > > > > > > > > > [] (sun6i_dsi_probe) from [] (platform_drv_probe+0x48/0x9c) > > > > > > > > > [] (platform_drv_probe) from [] (really_probe+0x1dc/0x2c8) > > > > > > > > > [] (really_probe) from [] (driver_probe_device+0x60/0x160) > > > > > > > > > [] (driver_probe_device) from [] (bus_for_each_drv+0x74/0xb8) > > > > > > > > > [] (bus_for_each_drv) from [] (__device_attach+0xd0/0x13c) > > > > > > > > > [] (__device_attach) from [] (bus_probe_device+0x84/0x8c) > > > > > > > > > [] (bus_probe_device) from [] (deferred_probe_work_func+0x64/0x90) > > > > > > > > > [] (deferred_probe_work_func) from [] (process_one_work+0x204/0x420) > > > > > > > > > [] (process_one_work) from [] (worker_thread+0x274/0x5a0) > > > > > > > > > [] (worker_thread) from [] (kthread+0x11c/0x14c) > > > > > > > > > [] (kthread) from [] (ret_from_fork+0x14/0x2c) > > > > > > > > > Exception stack(0xde539fb0 to 0xde539ff8) > > > > > > > > > 9fa0: 00000000 00000000 00000000 00000000 > > > > > > > > > 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 > > > > > > > > > 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 > > > > > > > > > ---[ end trace b57eb1e5c64c6b8b ]--- > > > > > > > > > random: fast init done > > > > > > > > > [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:46:crtc-0] flip_done timed out > > > > > > > > > [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CONNECTOR:48:DSI-1] flip_done timed out > > > > > > > > > [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [PLANE:30:plane-0] flip_done timed out > > > > > > > > > > > > > > > > > > But according to Allwinner A33, A64 BSP code [1] [3] the TCON DRQ for > > > > > > > > > non-burst DSI mode can be computed based on "horizontal front porch" > > > > > > > > > value only (no sync timings included). > > > > > > > > > > > > > > > > > > Detailed evidence for drq set bits based on A33 BSP [1] [2] > > > > > > > > > > > > > > > > > > => panel->lcd_ht - panel->lcd_x - panel->lcd_hbp - 20 > > > > > > > > > => (tt->hor_front_porch + lcdp->panel_info.lcd_hbp + > > > > > > > > > lcdp->panel_info.lcd_x) - panel->lcd_x - panel->lcd_hbp - 20 > > > > > > > > > => tt->hor_front_porch - 20 > > > > > > > > > > > > > > > > The thing is, while your explanation on the DRM side is sound, > > > > > > > > Allwinner has been using the hbp field of their panel description to > > > > > > > > store what DRM calls the backporch and the sync period. > > > > > > > > > > > > > > Exactly, hbp = backporch + sync > > > > > > > https://github.com/BPI-SINOVOIP/BPI-M2M-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp/de/disp_lcd.c#L2046 > > > > > > > > > > > > > > And the above computation is rely on that as well. If you can see the > > > > > > > final out of the above computation you can get the front porch value > > > > > > > (w/o sync ) > > > > > > > > > > > > As I was saying, you are explaining it well for DRM, but in order for > > > > > > your last formula (the one coming from the BSP) to make sense, you > > > > > > have to explain that the horizontal back porch for Allwinner contains > > > > > > the sync period, otherwise your expansion of lcd_ht doesn't make > > > > > > sense. > > > > > > > > > > I'm not sure why we need to take care of back porch since the formula > > > > > clearly evaluating a result as front porch, without sync timing (as > > > > > current code included this sync), I keep the hbp and trying to > > > > > substitute the lcd_ht value so the end result would cancel hbp. > > > > > > > > Because it changes how lcd_ht expands. In the DRM case, it will expand > > > > to the displayed area, the front porch, the sync period and the back > > > > porch. > > > > > > > > In your case, you expand it to the displayed area, the front porch and > > > > the back porch, precisely because in Allwinner's case, the back porch > > > > has the sync period. > > > > > > I understand the point, but technically it matter about the final > > > computation result. May be we can even manage the same computation in > > > back porch, but I'm not sure. Since the final output doesn't involve > > > any sync length, why we can include that ie what I'm not sure. > > > > We have the following formula: > > lcd_ht - lcd_x - lcd_hbp - 20 > > > > Using the concepts as they are defined in DRM, this expands to: > > x + hbp + hsync + hfp - x - hbp - 20 > > Here is diff between allwinner hbp vs hbp in DRM. > > Say hbp in DRM can call it hbackporch, so > > => x + hbackporch + hsync + hfp - -x - hbp - 20 > > (and here we need to substitute hbp formula from allwinner since the > actual equation would coming from there > https://github.com/BPI-SINOVOIP/BPI-M2M-bsp/blob/master/linux-sunxi/drivers/video/sunxi/disp/de/disp_lcd.c#L2046) And this is precisely what needs to be said, with an explanation about where that hor_back_porch is being used later on, and what impact it could have. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com --a2qaubfige6iysy4 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRcEzekXsqa64kGDp7j7w1vZxhRxQUCXQOzBgAKCRDj7w1vZxhR xe5sAQDQ/mAL8NjF8xehhe4V+7x59/0jNvqQJwYo4TzdH8BGDgD/e6Oa9PRc3cD4 +CyAQ4Rb95jwy+YSRoTlpZqIYoC4uwo= =wWH7 -----END PGP SIGNATURE----- --a2qaubfige6iysy4-- --===============0847348986080960914== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============0847348986080960914==--