Hi Tomeu,
>
> If we expose a render node for NPUs without rendering capabilities, the
> userspace stack will offer it to compositors and applications for
> rendering, which of course won't work.
>
> Userspace is probably right in not questioning whether a render node
> might not be capable of supporting rendering, so change it in the kernel
> instead by exposing a /dev/accel node.
>
> Before we bring the device up we don't know whether it is capable of
> rendering or not (depends on the features of its blocks), so first try
> to probe a rendering node, and if we find out that there is no rendering
> hardware, abort and retry with an accel node.
>
I really love this idea of moving away from a render node. What needs to be done
on the userspace side?
> Signed-off-by: Tomeu Vizoso <tomeu@xxxxxxxxxxxxxxx>
> Cc: Oded Gabbay <ogabbay@xxxxxxxxxx>
Reviewed-by: Christian Gmeiner <cgmeiner@xxxxxxxxxx>
> ---
> drivers/gpu/drm/etnaviv/etnaviv_drv.c | 46 ++++++++++++++++++++++-----
> 1 file changed, 38 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_drv.c b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> index 6500f3999c5f..8e7dd23115f4 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_drv.c
> @@ -11,6 +11,7 @@
> #include <linux/platform_device.h>
> #include <linux/uaccess.h>
>
> +#include <drm/drm_accel.h>
> #include <drm/drm_debugfs.h>
> #include <drm/drm_drv.h>
> #include <drm/drm_file.h>
> @@ -488,10 +489,10 @@ static const struct drm_ioctl_desc etnaviv_ioctls[] = {
> ETNA_IOCTL(PM_QUERY_SIG, pm_query_sig, DRM_RENDER_ALLOW),
> };
>
> -DEFINE_DRM_GEM_FOPS(fops);
> +DEFINE_DRM_GEM_FOPS(render_fops);
> +DEFINE_DRM_ACCEL_FOPS(accel_fops);
>
> -static const struct drm_driver etnaviv_drm_driver = {
> - .driver_features = DRIVER_GEM | DRIVER_RENDER,
> +static struct drm_driver etnaviv_drm_driver = {
> .open = etnaviv_open,
> .postclose = etnaviv_postclose,
> .gem_prime_import_sg_table = etnaviv_gem_prime_import_sg_table,
> @@ -500,7 +501,6 @@ static const struct drm_driver etnaviv_drm_driver = {
> #endif
> .ioctls = etnaviv_ioctls,
> .num_ioctls = DRM_ETNAVIV_NUM_IOCTLS,
> - .fops = &fops,
> .name = "etnaviv",
> .desc = "etnaviv DRM",
> .date = "20151214",
> @@ -508,15 +508,20 @@ static const struct drm_driver etnaviv_drm_driver = {
> .minor = 4,
> };
>
> -/*
> - * Platform driver:
> - */
> -static int etnaviv_bind(struct device *dev)
> +static int etnaviv_bind_with_type(struct device *dev, u32 type)
> {
> struct etnaviv_drm_private *priv;
> struct drm_device *drm;
> + bool is_compute_only = true;
> int ret;
>
> + etnaviv_drm_driver.driver_features = DRIVER_GEM | type;
> +
> + if (type == DRIVER_RENDER)
> + etnaviv_drm_driver.fops = &render_fops;
> + else
> + etnaviv_drm_driver.fops = &accel_fops;
> +
> drm = drm_dev_alloc(&etnaviv_drm_driver, dev);
> if (IS_ERR(drm))
> return PTR_ERR(drm);
> @@ -553,6 +558,18 @@ static int etnaviv_bind(struct device *dev)
>
> load_gpu(drm);
>
> + for (unsigned int i = 0; i < ETNA_MAX_PIPES; i++) {
> + struct etnaviv_gpu *g = priv->gpu[i];
> +
> + if (g && (g->identity.minor_features8 & chipMinorFeatures8_COMPUTE_ONLY) == 0)
> + is_compute_only = false;
> + }
> +
> + if (type == DRIVER_RENDER && is_compute_only) {
> + ret = -EINVAL;
> + goto out_unbind;
> + }
> +
> ret = drm_dev_register(drm, 0);
> if (ret)
> goto out_unbind;
> @@ -571,6 +588,19 @@ static int etnaviv_bind(struct device *dev)
> return ret;
> }
>
> +/*
> + * Platform driver:
> + */
> +static int etnaviv_bind(struct device *dev)
> +{
> + int ret = etnaviv_bind_with_type(dev, DRIVER_RENDER);
> +
> + if (ret == -EINVAL)
> + return etnaviv_bind_with_type(dev, DRIVER_COMPUTE_ACCEL);
> +
> + return ret;
> +}
> +
> static void etnaviv_unbind(struct device *dev)
> {
> struct drm_device *drm = dev_get_drvdata(dev);
> --
> 2.44.0
>
--
greets
--
Christian Gmeiner, MSc
https://christian-gmeiner.info/privacypolicy
