23.01.2019 12:39, Thierry Reding пишет:
> From: Thierry Reding <treding@xxxxxxxxxx>
>
> Loading the firmware requires an allocation of IOVA space to make sure
> that the VIC's Falcon microcontroller can read the firmware if address
> translation via the SMMU is enabled.
>
> However, the allocation currently happens at a time where the geometry
> of an IOMMU domain may not have been initialized yet. This happens for
> example on Tegra186 and later where an ARM SMMU is used. Domains which
> are created by the ARM SMMU driver postpone the geometry setup until a
> device is attached to the domain. This is because IOMMU domains aren't
> attached to a specific IOMMU instance at allocation time and hence the
> input address space, which defines the geometry, is not known yet.
>
> Work around this by postponing the firmware load until it is needed at
> the time where a channel is opened to the VIC. At this time the shared
> IOMMU domain's geometry has been properly initialized.
>
> As a byproduct this allows the Tegra DRM to be created in the absence
> of VIC firmware, since the VIC initialization no longer fails if the
> firmware can't be found.
>
> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
> ---
> drivers/gpu/drm/tegra/vic.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/tegra/vic.c b/drivers/gpu/drm/tegra/vic.c
> index d47983deb1cf..afbdc33f49bc 100644
> --- a/drivers/gpu/drm/tegra/vic.c
> +++ b/drivers/gpu/drm/tegra/vic.c
> @@ -181,13 +181,6 @@ static int vic_init(struct host1x_client *client)
> vic->domain = tegra->domain;
> }
>
> - if (!vic->falcon.data) {
> - vic->falcon.data = tegra;
> - err = falcon_load_firmware(&vic->falcon);
> - if (err < 0)
> - goto detach;
> - }
> -
> vic->channel = host1x_channel_request(client->dev);
> if (!vic->channel) {
> err = -ENOMEM;
> @@ -256,6 +249,16 @@ static int vic_open_channel(struct tegra_drm_client *client,
> if (err < 0)
> return err;
>
> + if (!vic->falcon.data) {
> + vic->falcon.data = client->drm;
> +
> + err = falcon_load_firmware(&vic->falcon);
> + if (err < 0) {
> + pm_runtime_put(vic->dev);
> + return err;
> + }
> + }
> +
> err = vic_boot(vic);
> if (err < 0) {
> pm_runtime_put(vic->dev);
>
This only moves the firmware data-copying to a later stage and doesn't touch reading out of the firmware file, hence the claim about the "byproduct" is invalid. Please take a look at the patch I posted sometime ago [0] and feel free to use it as a reference.
[0] https://patchwork.ozlabs.org/patch/1010389/
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