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RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Spam-Score: -4.51 Hi Am 22.10.25 um 16:06 schrieb Maxime Ripard: > Hi, > > On Wed, Oct 22, 2025 at 07:25:10PM +0530, Devarsh Thakkar wrote: >> On 08/09/25 14:43, Tomi Valkeinen wrote: >>> Currently when the driver's probe is called, we do a full DSS reset. If >>> the bootloader has set up a splash-screen, the reset will disable the >>> video output, and after that it may still take time until the display is >>> usable (all the kernel modules have been loaded) and even more time >>> until the userspace is able to use the display. >>> >>> If fbdev is enabled, in a perfect case tidss would take over the fb >>> memory set up by the bootloader, and use that memory for tidss's fbdev, >>> thus retaining the splash-screen. However, we're not there yet. >>> >>> As a partial solution, this patch changes the driver so that the driver >>> will not reset (or change) the DSS registers until tidss_runtime_get() >>> is called when the display is being set up (because of fbdev modesetting >>> or modesetting from the userspace). >>> >>> This is achieved in two parts: >>> >>> 1. Probe >>> >>> At probe time, in dispc_init_hw(), we check if the DSS is idle >>> (videoports disabled). If yes, do a reset and continue as before. If >>> not, we know that there's a splash-screen, and we set the >>> 'tidss->boot_enabled_vp_mask' field to reflect the enabled VPs. >>> >>> We then enable the corresponding VP clocks (to ensure they stay on), set >>> the IRQENABLE to 0 to make sure we won't get any interrupts, and then >>> exit leaving the fclk and VP clocks enabled, and the runtime PM status >>> active. >>> >>> 2. Runtime get >>> >>> Later, when the tidss_runtime_get() is called the first time, we check >>> the 'boot_enabled_vp_mask'. If set, we know that we have the >>> splash-screen showing on the screen, and thus the clocks are enabled and >>> runtime PM status is active. This indicates that >>> pm_runtime_resume_and_get() call just before in tidss_runtime_get() did >>> not cause a runtime_resume callback to get called, so we need to do that >>> manually. >>> >>> We call dispc_splash_fini() which essentially returns the DSS into the >>> state where it would be in a non-splash-screen case: dispc_splash_fini() >>> will do a DSS reset, manually call the runtime_resume callback, and then >>> call clk_disable_unprepare() and pm_runtime_put_noidle() to counter the >>> actions at probe time. >>> >>> Finally 'boot_enabled_vp_mask' is set to zero to mark that we're no >>> longer in the "splash-screen mode". >>> >>> A note about fbdev emulation: >>> >>> If fbdev emulation is enabled in the DRM, tidss will set up an fbdev. >>> This will cause a modeset, and the blank framebuffer from tidss's fbdev >>> will be shown instead of the splash-screen. >>> >>> I see two improvements to this: either we should memcpy the pixel data >>> from the bootloader's splash-screen to the new fbdev buffer, or the >>> fbdev could use the splash-screen directly as its buffer. I have done >>> some hacks for the former, but I'm not sure how to implement either of >>> these properly. > I still think it's not the kind of driver-specific driver behaviour we > want to have. > > Even more so when we have a generic solution to this problem in the > works. I agree with that sentiment. We want atomic-state readout plus a bootsplash DRM client. This would give us flicker-free booting with smooth transitions across drivers and user space. Best regards Thomas > > Maxime -- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)