Re: [PATCH v2 2/2] drm: zte: add initial vou drm driver

Emil Velikov
2016-09-30T12:34:14Z

Hi Shawn,

A couple of fly-by suggestions, which I hope you'll find useful :-)

On 24 September 2016 at 15:26, Shawn Guo <shawn.guo-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org> wrote:

> +
> + val = ((vm.hsync_len - 1) << SYNC_WIDE_SHIFT) & SYNC_WIDE_MASK;
To save some writing/minimise the chances to typos getting, in you can
have single/collection to static inline functions similar to msm [1].
On a similar note inline wrappers zte_read/write/mask (around
writel/readl) will provide quite useful for debugging/tracing :-)

[1] drivers/gpu/drm/msm/adreno/a4xx.xml.h

> + if (IS_ERR(zcrtc->pixclk))
> + return ERR_PTR(PTR_ERR(zcrtc->pixclk));
You might want to s/ERR_PTR(PTR_ERR// or s/ERR_PTR(PTR_ERR/ERR_CAST/
through the patch.

> +static int zx_drm_bind(struct device *dev)
> +{
> + struct drm_device *drm;
> + struct zx_drm_private *priv;
> + int ret;
> +
> + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> + if (!priv)
> + return -ENOMEM;
> +
> + drm = drm_dev_alloc(&zx_drm_driver, dev);
> + if (!drm)
> + return -ENOMEM;
> +
> + drm->dev_private = priv;
> + dev_set_drvdata(dev, drm);
> +
> + drm_mode_config_init(drm);
> + drm->mode_config.min_width = 16;
> + drm->mode_config.min_height = 16;
> + drm->mode_config.max_width = 4096;
> + drm->mode_config.max_height = 4096;
> + drm->mode_config.funcs = &zx_drm_mode_config_funcs;
> +
> + ret = drm_dev_register(drm, 0);
The documentation states that drm_dev_register() should be called
after the hardware is setup. which some drivers seems to interpret as
...

> + if (ret)
> + goto out_free;
> +
> + ret = component_bind_all(dev, drm);
> + if (ret) {
> + DRM_ERROR("Failed to bind all components\n");
> + goto out_unregister;
> + }
> +
> + ret = drm_vblank_init(drm, drm->mode_config.num_crtc);
> + if (ret < 0) {
> + DRM_ERROR("failed to initialise vblank\n");
> + goto out_unbind;
> + }
> +
> + /*
> + * We will manage irq handler on our own. In this case, irq_enabled
> + * need to be true for using vblank core support.
> + */
> + drm->irq_enabled = true;
> +
> + drm_mode_config_reset(drm);
> + drm_kms_helper_poll_init(drm);
> +
> + priv->fbdev = drm_fbdev_cma_init(drm, 32, drm->mode_config.num_crtc,
> + drm->mode_config.num_connector);
... calling it after these. If that's the correct case - perhaps we
can throw a WARN or similar within the above functions to catch
present/future misuse ?

> + if (IS_ERR(priv->fbdev)) {
> + ret = PTR_ERR(priv->fbdev);
> + priv->fbdev = NULL;
> + goto out_fini;
> + }
> +
> + return 0;
> +
> +out_fini:
> + drm_kms_helper_poll_fini(drm);
> + drm_mode_config_cleanup(drm);
> + drm_vblank_cleanup(drm);
> +out_unbind:
> + component_unbind_all(dev, drm);
> +out_unregister:
> + drm_dev_unregister(drm);
> +out_free:
> + dev_set_drvdata(dev, NULL);
> + drm_dev_unref(drm);
> + return ret;
> +}
> +
> +static void zx_drm_unbind(struct device *dev)
> +{
> + struct drm_device *drm = dev_get_drvdata(dev);
> + struct zx_drm_private *priv = drm->dev_private;
> +
> + if (priv->fbdev) {
> + drm_fbdev_cma_fini(priv->fbdev);
> + priv->fbdev = NULL;
> + }
> + drm_kms_helper_poll_fini(drm);
> + component_unbind_all(dev, drm);
> + drm_vblank_cleanup(drm);
> + drm_mode_config_cleanup(drm);
> + drm_dev_unregister(drm);
> + drm_dev_unref(drm);
> + drm->dev_private = NULL;
> + dev_set_drvdata(dev, NULL);
This and the teardown path in bind() are asymmetrical. Furthermore you
want to call drm_dev_unregister() first, according to its
documentation.
As mentioned above - perhaps it's worth providing feedback for drivers
which get the order wrong ?

> +static int zx_hdmi_bind(struct device *dev, struct device *master, void *data)
> +{

> +
> + clk_prepare_enable(hdmi->cec_clk);
> + clk_prepare_enable(hdmi->osc_clk);
> + clk_prepare_enable(hdmi->xclk);
> +
> + ret = zx_hdmi_register(drm, hdmi);
> + if (ret)
> + return ret;
> +

> + return 0;
> +}
> +
> +static void zx_hdmi_unbind(struct device *dev, struct device *master,
> + void *data)
> +{
> + struct zx_hdmi *hdmi = dev_get_drvdata(dev);
> +
> + clk_disable_unprepare(hdmi->cec_clk);
> + clk_disable_unprepare(hdmi->osc_clk);
> + clk_disable_unprepare(hdmi->xclk);
Nit: you want the teardown to happen in reverse order of the setup. I
might have missed a few similar cases within the patch, so please
double-check.

> +static int zx_gl_get_fmt(uint32_t format)
> +{
> + switch (format) {
> + case DRM_FORMAT_ARGB8888:
> + case DRM_FORMAT_XRGB8888:
> + return GL_FMT_ARGB8888;
> + case DRM_FORMAT_RGB888:
> + return GL_FMT_RGB888;
> + case DRM_FORMAT_RGB565:
> + return GL_FMT_RGB565;
> + case DRM_FORMAT_ARGB1555:
> + return GL_FMT_ARGB1555;
> + case DRM_FORMAT_ARGB4444:
> + return GL_FMT_ARGB4444;
> + default:
> + WARN_ONCE(1, "invalid pixel format %d\n", format);
> + return -EINVAL;
Afaics the only user of this is atomic_update() and that function
cannot fail. You might want to move this to the _check() function.
Same logic goes for the rest of the driver, in case I've missed any.

Regards,
Emil
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