[PATCH v5 04/10] drm/stm: Add STM32 LTDC driver

Benjamin Gaignard benjamin.gaignard at linaro.org
Wed Apr 12 11:58:56 PDT 2017


2017-04-11 22:45 GMT+02:00 Eric Anholt <eric at anholt.net>:
> Yannick Fertre <yannick.fertre at st.com> writes:
>
>> This controller provides output signals to interface directly a variety
>> of LCD and TFT panels. These output signals are: RGB signals
>> (up to 24bpp), vertical & horizontal synchronisations, data enable and
>> the pixel clock.
>>
>> Signed-off-by: Yannick Fertre <yannick.fertre at st.com>
>> ---
>>  drivers/gpu/drm/Kconfig      |    3 +-
>>  drivers/gpu/drm/Makefile     |    1 +
>>  drivers/gpu/drm/stm/Kconfig  |   16 +
>>  drivers/gpu/drm/stm/Makefile |    7 +
>>  drivers/gpu/drm/stm/drv.c    |  221 ++++++++
>>  drivers/gpu/drm/stm/ltdc.c   | 1210 ++++++++++++++++++++++++++++++++++++++++++
>>  drivers/gpu/drm/stm/ltdc.h   |   40 ++
>>  7 files changed, 1497 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/gpu/drm/stm/Kconfig
>>  create mode 100644 drivers/gpu/drm/stm/Makefile
>>  create mode 100644 drivers/gpu/drm/stm/drv.c
>>  create mode 100644 drivers/gpu/drm/stm/ltdc.c
>>  create mode 100644 drivers/gpu/drm/stm/ltdc.h
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 78d7fc0..dd5762a 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -203,7 +203,6 @@ config DRM_VGEM
>>         as used by Mesa's software renderer for enhanced performance.
>>         If M is selected the module will be called vgem.
>>
>> -
>
> Stray whitespace change.
>
> With this removed, the driver is:
>
> Reviewed-by: Eric Anholt <eric at anholt.net>
>
> Apologies for the delay in the second review offered.  The remainder of
> my comments are little cleanups, all of which I think are optional and
> fine to do after the code lands.
>
> You should probably update MAINTAINERS for your new driver.  If you'd
> like to maintain this driver in the drm-misc small drivers collection
> (https://01.org/linuxgraphics/gfx-docs/maintainer-tools/drm-misc.html),
> send a follow-up patch to the list to add the MAINTAINERS entry, and I
> can get that and patches 1-4 merged.  Once you have a few more patches
> in, we can add you to the drm-misc committers crew so you can merge
> directly after getting review.

Since we are moving sti driver to drm-misc it makes sense to move all
STMicroelectronic SoC display drivers to it.

>
> I'll also take this moment to plug something: Please feel welcome to
> review other people's driver patches on the list.  You've built
> something nice here, and probably learned a lot of lessons along the way
> that you could share with others.  (I just found out about
> of_reset_control in reviewing your code, and I wish I had known about it
> back when I was landing vc4!)
>
>> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
>> new file mode 100644
>> index 0000000..922f021
>> --- /dev/null
>> +++ b/drivers/gpu/drm/stm/ltdc.c
>
>> +static void ltdc_crtc_disable(struct drm_crtc *crtc)
>> +{
>> +     struct ltdc_device *ldev = crtc_to_ltdc(crtc);
>> +     struct drm_pending_vblank_event *event = crtc->state->event;
>> +
>> +     DRM_DEBUG_DRIVER("\n");
>> +
>> +     if (!crtc->enabled) {
>> +             DRM_DEBUG_DRIVER("already disabled\n");
>> +             return;
>> +     }
>
> I think this crtc->enabled is a given for the disable() being called.
>
>> +
>> +     drm_crtc_vblank_off(crtc);
>> +
>> +     /* disable LTDC */
>> +     reg_clear(ldev->regs, LTDC_GCR, GCR_LTDCEN);
>> +
>> +     /* disable IRQ */
>> +     reg_clear(ldev->regs, LTDC_IER, IER_RRIE | IER_FUIE | IER_TERRIE);
>> +
>> +     /* immediately commit disable of layers before switching off LTDC */
>> +     reg_set(ldev->regs, LTDC_SRCR, SRCR_IMR);
>> +
>> +     if (event) {
>> +             crtc->state->event = NULL;
>> +
>> +             spin_lock_irq(&crtc->dev->event_lock);
>> +             if (crtc->state->active && drm_crtc_vblank_get(crtc) == 0)
>> +                     drm_crtc_arm_vblank_event(crtc, event);
>> +             else
>> +                     drm_crtc_send_vblank_event(crtc, event);
>> +             spin_unlock_irq(&crtc->dev->event_lock);
>> +     }
>
> I believe that we're guaranteed that crtc->state->event is NULL in the
> disable call, since your atomic_flush() already armed or sent the event
> and NULLed out the pointer.
>
>> +struct drm_connector *ltdc_rgb_connector_create(struct drm_device *ddev)
>> +{
>> +     struct drm_connector *connector;
>> +     int err;
>> +
>> +     connector = devm_kzalloc(ddev->dev, sizeof(*connector), GFP_KERNEL);
>> +     if (!connector) {
>> +             DRM_ERROR("Failed to allocate connector\n");
>> +             return NULL;
>> +     }
>> +
>> +     connector->polled = DRM_CONNECTOR_POLL_HPD;
>> +
>> +     err = drm_connector_init(ddev, connector, &ltdc_rgb_connector_funcs,
>> +                              DRM_MODE_CONNECTOR_LVDS);
>
> I think DRM_MODE_CONNECTOR_DPI (and _ENCODER_DPI) are slightly more
> accurate descriptions, if I'm interpreting your pinmux setup right.
> It's cosmetic, though.
>
>> +static struct drm_panel *ltdc_get_panel(struct drm_device *ddev)
>> +{
>> +     struct device *dev = ddev->dev;
>> +     struct device_node *np = dev->of_node;
>> +     struct device_node *entity, *port = NULL;
>> +     struct drm_panel *panel = NULL;
>> +
>> +     DRM_DEBUG_DRIVER("\n");
>> +
>> +     /*
>> +      * Parse ltdc node to get remote port and find RGB panel / HDMI slave
>> +      * If a dsi or a bridge (hdmi, lvds...) is connected to ltdc,
>> +      * a remote port & RGB panel will not be found.
>> +      */
>> +     for_each_endpoint_of_node(np, entity) {
>> +             if (!of_device_is_available(entity))
>> +                     continue;
>> +
>> +             port = of_graph_get_remote_port_parent(entity);
>> +             if (port) {
>> +                     panel = of_drm_find_panel(port);
>> +                     of_node_put(port);
>> +                     if (panel) {
>> +                             DRM_DEBUG_DRIVER("remote panel %s\n",
>> +                                              port->full_name);
>> +                     } else {
>> +                             DRM_DEBUG_DRIVER("panel missing\n");
>> +                             of_node_put(entity);
>> +                     }
>> +             }
>> +     }
>
> Future work: You may find the new drm_of_find_panel_or_bridge() useful
> to drop this loop.
>
>> +
>> +     return panel;
>> +}
>> +
>> +int ltdc_load(struct drm_device *ddev)
>> +{
>> +     struct platform_device *pdev = to_platform_device(ddev->dev);
>> +     struct ltdc_device *ldev = ddev->dev_private;
>> +     struct device *dev = ddev->dev;
>> +     struct device_node *np = dev->of_node;
>> +     struct drm_encoder *encoder;
>> +     struct drm_connector *connector = NULL;
>> +     struct drm_crtc *crtc;
>> +     struct reset_control *rstc;
>> +     struct resource res;
>> +     int irq, ret, i;
>> +
>> +     DRM_DEBUG_DRIVER("\n");
>> +
>> +     ldev->panel = ltdc_get_panel(ddev);
>> +     if (!ldev->panel)
>> +             return -EPROBE_DEFER;
>> +
>> +     rstc = of_reset_control_get(np, NULL);
>> +
>> +     mutex_init(&ldev->err_lock);
>> +
>> +     ldev->pixel_clk = devm_clk_get(dev, "lcd");
>> +     if (IS_ERR(ldev->pixel_clk)) {
>> +             DRM_ERROR("Unable to get lcd clock\n");
>> +             return -ENODEV;
>> +     }
>> +
>> +     if (clk_prepare_enable(ldev->pixel_clk)) {
>> +             DRM_ERROR("Unable to prepare pixel clock\n");
>> +             return -ENODEV;
>> +     }
>
> Future work: You may want to move the pixel clock enable into the CRTC's
> .enable() and disable in .disable().  It sounded in previous versions
> like the HW uses that clock for all register accesses, so you'd need to
> protect a couple of other places, but that should save power when the
> device is off, right?
>
>> +
>> +     if (of_address_to_resource(np, 0, &res)) {
>> +             DRM_ERROR("Unable to get resource\n");
>> +             return -ENODEV;
>> +     }
>> +
>> +     ldev->regs = devm_ioremap_resource(dev, &res);
>> +     if (IS_ERR(ldev->regs)) {
>> +             DRM_ERROR("Unable to get ltdc registers\n");
>> +             return PTR_ERR(ldev->regs);
>> +     }
>> +
>> +     for (i = 0; i < MAX_IRQ; i++) {
>> +             irq = platform_get_irq(pdev, i);
>> +             if (irq < 0)
>> +                     continue;
>> +
>> +             ret = devm_request_threaded_irq(dev, irq, ltdc_irq,
>> +                                             ltdc_irq_thread, IRQF_ONESHOT,
>> +                                             dev_name(dev), ddev);
>> +             if (ret) {
>> +                     DRM_ERROR("Failed to register LTDC interrupt\n");
>> +                     return ret;
>> +             }
>> +     }
>> +
>> +     if (!IS_ERR(rstc))
>> +             reset_control_deassert(rstc);
>> +
>> +     /* Disable interrupts */
>> +     reg_clear(ldev->regs, LTDC_IER,
>> +               IER_LIE | IER_RRIE | IER_FUIE | IER_TERRIE);
>> +
>> +     ret = ltdc_get_caps(ddev);
>> +     if (ret) {
>> +             DRM_ERROR("hardware identifier (0x%08x) not supported!\n",
>> +                       ldev->caps.hw_version);
>> +             return ret;
>> +     }
>> +
>> +     DRM_INFO("ltdc hw version 0x%08x - ready\n", ldev->caps.hw_version);
>> +
>> +     if (ltdc_create_encoders(ddev)) {
>> +             DRM_ERROR("Failed to create encoders\n");
>> +             return -EINVAL;
>> +     }
>> +
>> +     if (ldev->panel) {
>> +             encoder = ltdc_rgb_encoder_find(ddev);
>> +             if (!encoder) {
>> +                     DRM_ERROR("Failed to find RGB encoder\n");
>> +                     ret = -EINVAL;
>> +                     goto err;
>> +             }
>
> Given that ltdc_create_encoders() only does work if ldev->panel, its
> body could probably be moved in here and then ltdc_rgb_encoder_find
> could be dropped.
>
>> +
>> +             connector = ltdc_rgb_connector_create(ddev);
>> +             if (!connector) {
>> +                     DRM_ERROR("Failed to create RGB connector\n");
>> +                     ret = -EINVAL;
>> +                     goto err;
>> +             }
>> +
>> +             ret = drm_mode_connector_attach_encoder(connector, encoder);
>> +             if (ret) {
>> +                     DRM_ERROR("Failed to attach connector to encoder\n");
>> +                     goto err;
>> +             }
>> +
>> +             drm_panel_attach(ldev->panel, connector);
>> +     }
>
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>



-- 
Benjamin Gaignard

Graphic Study Group

Linaro.org │ Open source software for ARM SoCs

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