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

From: Maxime Ripard
Date: Thu Mar 09 2017 - 09:41:19 EST

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On Thu, Mar 09, 2017 at 07:20:30PM +0800, Chen-Yu Tsai wrote:
> On Thu, Mar 9, 2017 at 6:36 PM, Maxime Ripard
> <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> > 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@xxxxxxxx>
> >> ---
> >> 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.
>
> Yes. I seem to have forgotten that bit which I had intended to add.
> The endpoint IDs would ideally match the actual mux values used.

That works for me, but the binding documentation would need to be
amended.

> On the TCON side that's not doable, so we might have to just require
> them being in an increasing order.

What are you planning to use those IDs on for the TCON?

>
> > 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.
>
> Yes that would work for the above purposes.
>
> For getting the first TCON to access the mux registers, it kind of falls
> short. We also need something like this for the TV encoders on A10/A20.
> They too have a mux, which seems to be in the first TV encoder. This
> controls how the 8 DACs are mapped to the 4 external pins.

How are those pins muxed between the two? Can't we just create a
connector that would be usable for both encoders?

Maxime

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

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Next message: Vignesh R: "Re: [PATCH] serial: 8250: 8250_core: Use dev_name() during request_irq()"
Previous message: Richard Guy Briggs: "[PATCH] audit: log module name on delete_module"
In reply to: Chen-Yu Tsai: "Re: [PATCH 09/11] drm/sun4i: Support two display pipelines"
Next in thread: Chen-Yu Tsai: "[PATCH 08/11] drm/sun4i: Fetch TCON ID from device tree"
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