[PATCH 09/11] drm/sun4i: Support two display pipelines

Maxime Ripard
2017-03-09T10:36:36Z

Hi,

On Thu, Mar 09, 2017 at 06:05:32PM +0800, Chen-Yu Tsai wrote:
> Some Allwinner SoCs have two display pipelines (frontend -> backend ->
> tcon).
>
> Previously we only supported one pipeline. This patch extends the
> current driver to support two. It extends the tcon and backend pointers
> in sun4i_drv into arrays, and makes the related bind functions store
> the pointer into said arrays based on the id fetched from the device
> tree. In the case of the tcons, it falls back to a first come order
> if no encoders that can be used for differentiating the tcons are
> defined. The driver's depth-first traversal of the of graph, coupled
> with the increasing address ordering of the of graph endpoints, and
> the fact that tcon0 should always be enabled for the tcon/encoder
> mux to be accessible, means that tcon1 would always come after tcon0.
>
> Assignment of the device structure into sun4i_drv is moved to the end
> of the bind function, when all possible error checks have passed.
>
> This patch also drops a trailing 0 in one of the backend probe messages.
>
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>
> ---
> drivers/gpu/drm/sun4i/sun4i_backend.c | 9 +++++++--
> drivers/gpu/drm/sun4i/sun4i_drv.c | 2 +-
> drivers/gpu/drm/sun4i/sun4i_drv.h | 6 ++++--
> drivers/gpu/drm/sun4i/sun4i_tcon.c | 25 +++++++++++++++++--------
> 4 files changed, 29 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/sun4i/sun4i_backend.c b/drivers/gpu/drm/sun4i/sun4i_backend.c
> index f3c92d54c8e4..8d22efd5a9cc 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_backend.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
> @@ -350,12 +350,15 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
> if (!backend)
> return -ENOMEM;
> dev_set_drvdata(dev, backend);
> - drv->backend = backend;
>
> backend->id = sun4i_backend_of_get_id(dev->of_node);
> if (backend->id < 0)
> return backend->id;
>
> + /* We only support SUN4I_DRM_MAX_PIPELINES number of backends */
> + if (backend->id >= SUN4I_DRM_MAX_PIPELINES)
> + return -EINVAL;
> +
> res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> regs = devm_ioremap_resource(dev, res);
> if (IS_ERR(regs))
> @@ -364,7 +367,7 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
> backend->regs = devm_regmap_init_mmio(dev, regs,
> &sun4i_backend_regmap_config);
> if (IS_ERR(backend->regs)) {
> - dev_err(dev, "Couldn't create the backend0 regmap\n");
> + dev_err(dev, "Couldn't create the backend regmap\n");
> return PTR_ERR(backend->regs);
> }
>
> @@ -413,6 +416,8 @@ static int sun4i_backend_bind(struct device *dev, struct device *master,
> }
> }
>
> + drv->backend[backend->id] = backend;
> +
> /* Reset the registers */
> for (i = 0x800; i < 0x1000; i += 4)
> regmap_write(backend->regs, i, 0);
> diff --git a/drivers/gpu/drm/sun4i/sun4i_drv.c b/drivers/gpu/drm/sun4i/sun4i_drv.c
> index 767bbadcc85d..c15ecb8343d7 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_drv.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_drv.c
> @@ -271,7 +271,7 @@ static int sun4i_drv_probe(struct platform_device *pdev)
> struct device_node *np = pdev->dev.of_node;
> int i, count = 0;
>
> - for (i = 0;; i++) {
> + for (i = 0; i < SUN4I_DRM_MAX_PIPELINES; i++) {
> struct device_node *pipeline = of_parse_phandle(np,
> "allwinner,pipelines",
> i);
> diff --git a/drivers/gpu/drm/sun4i/sun4i_drv.h b/drivers/gpu/drm/sun4i/sun4i_drv.h
> index 5df50126ff52..ec1c08af47e1 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_drv.h
> +++ b/drivers/gpu/drm/sun4i/sun4i_drv.h
> @@ -16,9 +16,11 @@
> #include <linux/clk.h>
> #include <linux/regmap.h>
>
> +#define SUN4I_DRM_MAX_PIPELINES 2
> +
> struct sun4i_drv {
> - struct sun4i_backend *backend;
> - struct sun4i_tcon *tcon;
> + struct sun4i_backend *backend[SUN4I_DRM_MAX_PIPELINES];
> + struct sun4i_tcon *tcon[SUN4I_DRM_MAX_PIPELINES];
>
> struct drm_fbdev_cma *fbdev;
> };
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index b774c9a50c55..7749c3133f38 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -532,7 +532,6 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
> if (!tcon)
> return -ENOMEM;
> dev_set_drvdata(dev, tcon);
> - drv->tcon = tcon;
> tcon->drm = drm;
> tcon->dev = dev;
> tcon->quirks = of_device_get_match_data(dev);
> @@ -540,14 +539,22 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
> /* This can fail if the DT does not have any downstream encoders. */
> tcon->id = sun4i_tcon_of_get_id(dev->of_node);
> if (tcon->id < 0) {
> - /*
> - * TODO We currently support only 1 TCON, so we can
> - * safely set this to 0. This should be revisited
> - * when we add support for multiple pipelines.
> - */
> - tcon->id = 0;
> + int i;
> +
> + /* find the first empty tcon in sun4i_drv */
> + for (i = 0; i < SUN4I_DRM_MAX_PIPELINES; i++)
> + if (!drv->tcon[i])
> + tcon->id = i;
> +
> + /* bail out if that failed */
> + if (tcon->id < 0)
> + return tcon->id;
> }
>
> + /* We only support SUN4I_DRM_MAX_PIPELINES number of tcons */
> + if (tcon->id >= SUN4I_DRM_MAX_PIPELINES)
> + return -EINVAL;
> +
> tcon->lcd_rst = devm_reset_control_get(dev, "lcd");
> if (IS_ERR(tcon->lcd_rst)) {
> dev_err(dev, "Couldn't get our reset line\n");
> @@ -588,7 +595,7 @@ static int sun4i_tcon_bind(struct device *dev, struct device *master,
> goto err_free_dotclock;
> }
>
> - tcon->crtc = sun4i_crtc_init(drm, drv->backend, tcon);
> + tcon->crtc = sun4i_crtc_init(drm, drv->backend[tcon->id], tcon);

I'm not a big fan of those IDs. The heuristic seems to be a bit
fragile since we really never enforced any order in our bindings.

You seem to use it for two things:
- to match a TCON to its backend in our code
- to not step on each others' toes when registering the backends/tcons

I think the second could be easily addressed using a linked list, and
the first one by storing the of_node. Then we just need to follow the
OF graph to our input of_node, and then iterate through our registered
backend list to find the one with the same of_node.

Maxime

--
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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