Re: [PATCH v6 3/5] drm/vc4: Set up the DSI host at pdev probe time, not component bind.

Boris Brezillon
2017-10-11T12:01:27Z

On Tue, 15 Aug 2017 16:47:20 -0700
Eric Anholt <eric@anholt.net> wrote:

> We need the following things to happen in sequence:
>
> DSI host creation
> DSI device creation in the panel driver (needs DSI host)
> DSI device attach from panel to host.
> DSI drm_panel_add()
> DSI encoder creation
> DSI encoder's DRM panel/bridge attach
>
> Unless we allow device creation while the host isn't up yet, we need
> to break the -EPROBE_DEFER deadlock between the panel driver looking
> up the host and the host driver looking up the panel. We can do so by
> moving the DSI host creation outside of the component bind loop, and
> the panel/bridge lookup/attach into the component bind process.
>
> Signed-off-by: Eric Anholt <eric@anholt.net>

Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> ---
> drivers/gpu/drm/vc4/vc4_dsi.c | 97 +++++++++++++++++++++++++------------------
> 1 file changed, 57 insertions(+), 40 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_dsi.c b/drivers/gpu/drm/vc4/vc4_dsi.c
> index 2516cd3a1d87..ec1d646b3151 100644
> --- a/drivers/gpu/drm/vc4/vc4_dsi.c
> +++ b/drivers/gpu/drm/vc4/vc4_dsi.c
> @@ -33,6 +33,7 @@
> #include <drm/drm_crtc_helper.h>
> #include <drm/drm_edid.h>
> #include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_of.h>
> #include <drm/drm_panel.h>
> #include <linux/clk.h>
> #include <linux/clk-provider.h>
> @@ -504,7 +505,6 @@ struct vc4_dsi {
> struct mipi_dsi_host dsi_host;
> struct drm_encoder *encoder;
> struct drm_bridge *bridge;
> - bool is_panel_bridge;
>
> void __iomem *regs;
>
> @@ -1289,7 +1289,6 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
> struct mipi_dsi_device *device)
> {
> struct vc4_dsi *dsi = host_to_dsi(host);
> - int ret = 0;
>
> dsi->lanes = device->lanes;
> dsi->channel = device->channel;
> @@ -1324,34 +1323,12 @@ static int vc4_dsi_host_attach(struct mipi_dsi_host *host,
> return 0;
> }
>
> - dsi->bridge = of_drm_find_bridge(device->dev.of_node);
> - if (!dsi->bridge) {
> - struct drm_panel *panel =
> - of_drm_find_panel(device->dev.of_node);
> -
> - dsi->bridge = drm_panel_bridge_add(panel,
> - DRM_MODE_CONNECTOR_DSI);
> - if (IS_ERR(dsi->bridge)) {
> - ret = PTR_ERR(dsi->bridge);
> - dsi->bridge = NULL;
> - return ret;
> - }
> - dsi->is_panel_bridge = true;
> - }
> -
> - return drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);
> + return 0;
> }
>
> static int vc4_dsi_host_detach(struct mipi_dsi_host *host,
> struct mipi_dsi_device *device)
> {
> - struct vc4_dsi *dsi = host_to_dsi(host);
> -
> - if (dsi->is_panel_bridge) {
> - drm_panel_bridge_remove(dsi->bridge);
> - dsi->bridge = NULL;
> - }
> -
> return 0;
> }
>
> @@ -1493,16 +1470,13 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
> struct platform_device *pdev = to_platform_device(dev);
> struct drm_device *drm = dev_get_drvdata(master);
> struct vc4_dev *vc4 = to_vc4_dev(drm);
> - struct vc4_dsi *dsi;
> + struct vc4_dsi *dsi = dev_get_drvdata(dev);
> struct vc4_dsi_encoder *vc4_dsi_encoder;
> + struct drm_panel *panel;
> const struct of_device_id *match;
> dma_cap_mask_t dma_mask;
> int ret;
>
> - dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> - if (!dsi)
> - return -ENOMEM;
> -
> match = of_match_device(vc4_dsi_dt_match, dev);
> if (!match)
> return -ENODEV;
> @@ -1517,7 +1491,6 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
> vc4_dsi_encoder->dsi = dsi;
> dsi->encoder = &vc4_dsi_encoder->base.base;
>
> - dsi->pdev = pdev;
> dsi->regs = vc4_ioremap_regs(pdev, 0);
> if (IS_ERR(dsi->regs))
> return PTR_ERR(dsi->regs);
> @@ -1598,6 +1571,18 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
> return ret;
> }
>
> + ret = drm_of_find_panel_or_bridge(dev->of_node, 0, 0,
> + &panel, &dsi->bridge);
> + if (ret)
> + return ret;
> +
> + if (panel) {
> + dsi->bridge = devm_drm_panel_bridge_add(dev, panel,
> + DRM_MODE_CONNECTOR_DSI);
> + if (IS_ERR(dsi->bridge))
> + return PTR_ERR(dsi->bridge);
> + }
> +
> /* The esc clock rate is supposed to always be 100Mhz. */
> ret = clk_set_rate(dsi->escape_clock, 100 * 1000000);
> if (ret) {
> @@ -1616,12 +1601,11 @@ static int vc4_dsi_bind(struct device *dev, struct device *master, void *data)
> DRM_MODE_ENCODER_DSI, NULL);
> drm_encoder_helper_add(dsi->encoder, &vc4_dsi_encoder_helper_funcs);
>
> - dsi->dsi_host.ops = &vc4_dsi_host_ops;
> - dsi->dsi_host.dev = dev;
> -
> - mipi_dsi_host_register(&dsi->dsi_host);
> -
> - dev_set_drvdata(dev, dsi);
> + ret = drm_bridge_attach(dsi->encoder, dsi->bridge, NULL);
> + if (ret) {
> + dev_err(dev, "bridge attach failed: %d\n", ret);
> + return ret;
> + }
>
> pm_runtime_enable(dev);
>
> @@ -1639,8 +1623,6 @@ static void vc4_dsi_unbind(struct device *dev, struct device *master,
>
> vc4_dsi_encoder_destroy(dsi->encoder);
>
> - mipi_dsi_host_unregister(&dsi->dsi_host);
> -
> if (dsi->port == 1)
> vc4->dsi1 = NULL;
> }
> @@ -1652,12 +1634,47 @@ static const struct component_ops vc4_dsi_ops = {
>
> static int vc4_dsi_dev_probe(struct platform_device *pdev)
> {
> - return component_add(&pdev->dev, &vc4_dsi_ops);
> + struct device *dev = &pdev->dev;
> + struct vc4_dsi *dsi;
> + int ret;
> +
> + dsi = devm_kzalloc(dev, sizeof(*dsi), GFP_KERNEL);
> + if (!dsi)
> + return -ENOMEM;
> + dev_set_drvdata(dev, dsi);
> +
> + dsi->pdev = pdev;
> +
> + /* Note, the initialization sequence for DSI and panels is
> + * tricky. The component bind above won't get past its
> + * -EPROBE_DEFER until the panel/bridge probes. The
> + * panel/bridge will return -EPROBE_DEFER until it has a
> + * mipi_dsi_host to register its device to. So, we register
> + * the host during pdev probe time, so vc4 as a whole can then
> + * -EPROBE_DEFER its component bind process until the panel
> + * successfully attaches.
> + */
> + dsi->dsi_host.ops = &vc4_dsi_host_ops;
> + dsi->dsi_host.dev = dev;
> + mipi_dsi_host_register(&dsi->dsi_host);
> +
> + ret = component_add(&pdev->dev, &vc4_dsi_ops);
> + if (ret) {
> + mipi_dsi_host_unregister(&dsi->dsi_host);
> + return ret;
> + }
> +
> + return 0;
> }
>
> static int vc4_dsi_dev_remove(struct platform_device *pdev)
> {
> + struct device *dev = &pdev->dev;
> + struct vc4_dsi *dsi = dev_get_drvdata(dev);
> +
> component_del(&pdev->dev, &vc4_dsi_ops);
> + mipi_dsi_host_unregister(&dsi->dsi_host);
> +
> return 0;
> }
>