On Wed, Mar 28, 2018 at 09:34:54AM +0200, Boris Brezillon wrote: > Hi Peter, > > On Mon, 26 Mar 2018 09:35:02 +0200 > Peter Rosin <peda@xxxxxxxxxx> wrote: > > > I have an sama5d31-based system with 64MB of memory and a 1920x1080 > > LVDS display wired for 16-bpp. When I enable legacy fbdev support, > > the contiguous memory allocator invariably fails with the order-11 > > allocation for a 1920x1080@24-bpp buffer (~6MB). But this HW can never > > make any good use of RGB888, so that is a wasted attempt anyway that > > would also waste precious memory should it succeed. > > > > Sure, I could rewrite user-space to go directly to KMS etc, and that > > makes the (attempted) order-11 allocation go away, replacing it with > > one order-10 allocation per application restart for a 1920x1080@16-bpp > > buffer (<4MB). But after a few restarts, order-10 allocations start to > > fail as well, which is only to be expected AFAIU. > > > > So, I'd rather not change user-space (which was originally written > > to target a smaller display) so that I at the same time get the > > benefit of an early pre-allocated fbdev frame-buffer that can be > > reused over and over. But to do that I need to tell the driver that > > 16-bpp is the preferred depth. Add a module parameter to do just that. > > > > Signed-off-by: Peter Rosin <peda@xxxxxxxxxx> > > --- > > drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c | 18 +++++++++++++++++- > > 1 file changed, 17 insertions(+), 1 deletion(-) > > > > I found some inspiration regarding naming and implementation here: > > https://patchwork.kernel.org/patch/9848631/ > > > > I have found no feedback on that patch though, which makes me wonder if > > I'm perhaps barking up the wronig tree? > > Hm, isn't that something you can already overload with the video= > parameter? > > video=<output>:<resolution>[-<bpp>] > > AFAIR, <bpp> encodes the color depth, so what is the benefit of adding > this new property to overload the default depth? > > Maybe I'm wrong and the default depth param is actually useful, but in > this case we should probably make it generic since other drivers seems > to need it too, and we might want to attach it to a specific display > engine instance. I think for the drm's fbdev emulation we ignore the bpp ... But yeah probably worth it to wire it up properly. -Daniel > > Thanks, > > Boris > > > > > Cheers, > > Peter > > > > diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c > > index c1ea5c36b006..f0148627c221 100644 > > --- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c > > +++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_dc.c > > @@ -29,6 +29,11 @@ > > > > #define ATMEL_HLCDC_LAYER_IRQS_OFFSET 8 > > > > +static int atmel_hlcdc_preferred_depth __read_mostly; > > + > > +MODULE_PARM_DESC(preferreddepth, "Set preferred bpp"); > > +module_param_named(preferreddepth, atmel_hlcdc_preferred_depth, int, 0400); > > + > > static const struct atmel_hlcdc_layer_desc atmel_hlcdc_at91sam9n12_layers[] = { > > { > > .name = "base", > > @@ -590,6 +595,7 @@ static int atmel_hlcdc_dc_modeset_init(struct drm_device *dev) > > dev->mode_config.min_height = dc->desc->min_height; > > dev->mode_config.max_width = dc->desc->max_width; > > dev->mode_config.max_height = dc->desc->max_height; > > + dev->mode_config.preferred_depth = 24; > > dev->mode_config.funcs = &mode_config_funcs; > > > > return 0; > > @@ -658,7 +664,7 @@ static int atmel_hlcdc_dc_load(struct drm_device *dev) > > > > platform_set_drvdata(pdev, dev); > > > > - drm_fb_cma_fbdev_init(dev, 24, 0); > > + drm_fb_cma_fbdev_init(dev, atmel_hlcdc_preferred_depth, 0); > > > > drm_kms_helper_poll_init(dev); > > > > @@ -756,6 +762,16 @@ static int atmel_hlcdc_dc_drm_probe(struct platform_device *pdev) > > struct drm_device *ddev; > > int ret; > > > > + switch (atmel_hlcdc_preferred_depth) { > > + case 0: /* driver default */ > > + case 8: > > + case 16: > > + case 24: > > + break; > > + default: > > + return -EINVAL; > > + } > > + > > ddev = drm_dev_alloc(&atmel_hlcdc_dc_driver, &pdev->dev); > > if (IS_ERR(ddev)) > > return PTR_ERR(ddev); > > > > -- > Boris Brezillon, Bootlin (formerly Free Electrons) > Embedded Linux and Kernel engineering > https://bootlin.com > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
