On Fri, 2019-01-11 at 17:07 +0100, Noralf Trønnes wrote: > > Den 11.01.2019 11.25, skrev Daniel Vetter: > > On Fri, Jan 11, 2019 at 05:49:15PM +0800, CK Hu wrote: > >> Hi, Daniel: > >> > >> On Fri, 2019-01-11 at 10:20 +0100, Daniel Vetter wrote: > >>> On Fri, Jan 11, 2019 at 11:20:09AM +0800, CK Hu wrote: > >>>> Hi, Daniel: > >>>> > >>>> On Thu, 2019-01-10 at 21:02 +0100, Daniel Vetter wrote: > >>>>> On Thu, Jan 10, 2019 at 08:01:37PM +0100, Frank Wunderlich wrote: > >>>>>> Hi Daniel, > >>>>>> > >>>>>>>> Would be good to use the new generic fbdev emulation code here, for even > >>>>>>>> less code. Or at least know why this isn't possible to use for mtk (and > >>>>>>>> maybe address that in the core code). Hand-rolling fbdev code shouldn't be > >>>>>>>> needed anymore. > >>>>>>> > >>>>>>> Back on the mailing list, no private replies please: > >>>>>> > >>>>>> i don't wanted to spam all people with dumb questions ;) > >>>>> > >>>>> There's no dumb questions, only insufficient documentation :-) > >>>>> > >>>>>>> For examples please grep for drm_fbdev_generic_setup(). There's also a > >>>>>>> still in-flight series from Gerd Hoffmann to convert over bochs. That, > >>>>>>> plus all the kerneldoc linked from there should get you started. > >>>>>>> -Daniel > >>>>>> > >>>>>> this is one of google best founds if i search for drm_fbdev_generic_setup: > >>>>>> > >>>>>> https://lkml.org/lkml/2018/12/19/305 > >>>>>> > >>>>>> not very helpful... > >>>>>> > >>>>>> so i tried kernel-doc > >>>>>> > >>>>>> https://www.kernel.org/doc/html/latest/gpu/drm-kms-helpers.html?highlight=drm_fbdev_generic_setup#c.drm_fbdev_generic_setup > >>>>>> > >>>>>> which is nice function-reference but i've found no generic workflow > >>>>>> > >>>>>> as the posted driver is "only" a driver ported from kernel 4.4 by Alexander, i don't know if this new framework can be used and which parts need to be changed. I only try to bring his code Mainline.... > >>>>>> Maybe CK Hu can help here because driver is originally from him and he knows internals. Or maybe you can help here? > >>>>>> > >>>>>> i personally make my first steps as spare-time kernel-developer :) > >>>>> > >>>>> There's a ton of in-kernel users of that function already, I meant you can > >>>>> use those to serve as examples ... If those + the kerneldoc aren't > >>>>> good enough, then we need to improve them. > >>>>> -Daniel > >>>> > >>>> I've tried with drm_fbdev_generic_setup() and it works fine with simple > >>>> modification. The patch is > >>>> > >>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c > >>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c > >>>> @@ -16,6 +16,7 @@ > >>>> #include <drm/drm_atomic.h> > >>>> #include <drm/drm_atomic_helper.h> > >>>> #include <drm/drm_crtc_helper.h> > >>>> +#include <drm/drm_fb_helper.h> > >>>> #include <drm/drm_gem.h> > >>>> #include <drm/drm_gem_cma_helper.h> > >>>> #include <drm/drm_of.h> > >>>> @@ -379,6 +380,7 @@ static void mtk_drm_kms_deinit(struct drm_device > >>>> *drm) > >>>> .gem_prime_get_sg_table = mtk_gem_prime_get_sg_table, > >>>> .gem_prime_import_sg_table = mtk_gem_prime_import_sg_table, > >>>> .gem_prime_mmap = mtk_drm_gem_mmap_buf, > >>>> + .gem_prime_vmap = mtk_drm_gem_prime_vmap, > >>>> .ioctls = mtk_ioctls, > >>>> .num_ioctls = ARRAY_SIZE(mtk_ioctls), > >>>> .fops = &mtk_drm_fops, > >>>> @@ -416,6 +418,8 @@ static int mtk_drm_bind(struct device *dev) > >>>> if (ret < 0) > >>>> goto err_deinit; > >>>> > >>>> + drm_fbdev_generic_setup(drm, 32); > >>>> + > >>>> return 0; > >>>> > >>>> > >>>> But I implement .gem_prime_vmap with a workaround, > >>>> > >>>> > >>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_gem.c > >>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_gem.c > >>>> @@ -280,3 +280,8 @@ int mtk_gem_create_ioctl(struct drm_device *dev, > >>>> void *data, > >>>> mtk_drm_gem_free_object(&mtk_gem->base); > >>>> return ret; > >>>> } > >>>> + > >>>> +void *mtk_drm_gem_prime_vmap(struct drm_gem_object *obj) > >>>> +{ > >>>> + return (void *)1; > >>>> +} > >>>> > >>>> Current drm_fb_helper depends on drm_client to create fbdev. When > >>>> drm_client create drm_client_buffer, it need to vmap to get kernel > >>>> vaddr. But I think for fbdev, the vaddr is useless. Do you agree that I > >>>> temporarily implement .gem_prime_vmap in such way? > >>> > >>> The vmap is used by fbcon, without that fbdev won't really work I think. > >>> So I'm rather confused on what you tested ... > >>> > >>> Adding Noralf, he's the expert here. > >>> -Daniel > >> > >> I test with fb_test [1], it is a user space program just open /dev/fb0 > >> and mmap it to user space. I does not turn on fbcon so everything looks > >> well. If support fbcon is essential, I would implement vmap correctly. > >> If it's not essential, I think I could return 0 when > >> CONFIG_FRAMBUFFER_CONSOLE is defined. > > > > I think fbdev emulation without working fbcon is fairly useless. And it > > shouldn't be that much work to make it work, we have quite a few more > > helers for gem bo nowadays. > > If the virtual address is not set, fbcon can't be used and that means it > has to be disabled using something like this in the driver Kconfig: > depends on !FRAMEBUFFER_CONSOLE > > Otherwise it will crash if someone tries to use it. > > The problem here is that this driver doesn't map a virtual address for > its buffers: > mtk_gem->dma_attrs |= DMA_ATTR_NO_KERNEL_MAPPING; > > Probably because of limited virtual address space. > rockchip is in the same situation. > > I'm aware of this shortcoming of the generic emulation, but I don't see > how it can be solved without using somekind of flag attached to the dumb > buffer creation request. The virtual address space is limited so we do not map it by default. I also see the shortcoming of the generic emulation, so I would refer to rockchip to implement this mapping. Regards, CK > > Noralf. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
