Re: [PATCH 02/14] drm/arm/hdlcd: Convert to Linux IRQ interfaces

Hi Sam

Am 28.07.21 um 15:31 schrieb Sam Ravnborg:

Hi Thomas,

On Tue, Jul 27, 2021 at 08:27:09PM +0200, Thomas Zimmermann wrote:

...

Drop the DRM IRQ midlayer in favor of Linux IRQ interfaces. DRM's IRQ helpers are mostly useful for UMS drivers. Modern KMS drivers don't benefit from using it.

DRM IRQ callbacks are now being called directly or inlined.

Calls to platform_get_irq() can fail with a negative errno code. Abort initialization in this case. The DRM IRQ midlayer does not handle this case correctly.

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

drivers/gpu/drm/arm/hdlcd_drv.c | 174 ++++++++++++++++++-------------- drivers/gpu/drm/arm/hdlcd_drv.h | 1 + 2 files changed, 97 insertions(+), 78 deletions(-)

diff --git a/drivers/gpu/drm/arm/hdlcd_drv.c b/drivers/gpu/drm/arm/hdlcd_drv.c index 81ae92390736..b9998fe3982f 100644 --- a/drivers/gpu/drm/arm/hdlcd_drv.c +++ b/drivers/gpu/drm/arm/hdlcd_drv.c @@ -29,7 +29,6 @@ #include <drm/drm_fb_helper.h> #include <drm/drm_gem_cma_helper.h> #include <drm/drm_gem_framebuffer_helper.h> -#include <drm/drm_irq.h> #include <drm/drm_modeset_helper.h> #include <drm/drm_of.h> #include <drm/drm_probe_helper.h> @@ -38,6 +37,94 @@ #include "hdlcd_drv.h" #include "hdlcd_regs.h"

+static irqreturn_t hdlcd_irq(int irq, void *arg) +{

• struct drm_device *drm = arg;
• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• unsigned long irq_status;
• irq_status = hdlcd_read(hdlcd, HDLCD_REG_INT_STATUS);

+#ifdef CONFIG_DEBUG_FS

• if (irq_status & HDLCD_INTERRUPT_UNDERRUN)

• atomic_inc(&hdlcd->buffer_underrun_count);
  

• if (irq_status & HDLCD_INTERRUPT_DMA_END)

• atomic_inc(&hdlcd->dma_end_count);
  

• if (irq_status & HDLCD_INTERRUPT_BUS_ERROR)

• atomic_inc(&hdlcd->bus_error_count);
  

• if (irq_status & HDLCD_INTERRUPT_VSYNC)

• atomic_inc(&hdlcd->vsync_count);
  

+#endif

• if (irq_status & HDLCD_INTERRUPT_VSYNC)

• drm_crtc_handle_vblank(&hdlcd->crtc);
  

• /* acknowledge interrupt(s) */
• hdlcd_write(hdlcd, HDLCD_REG_INT_CLEAR, irq_status);
• return IRQ_HANDLED;

+}

+static void hdlcd_irq_preinstall(struct drm_device *drm) +{

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• /* Ensure interrupts are disabled */
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, 0);
• hdlcd_write(hdlcd, HDLCD_REG_INT_CLEAR, ~0);

+}

+static void hdlcd_irq_postinstall(struct drm_device *drm) +{ +#ifdef CONFIG_DEBUG_FS

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• unsigned long irq_mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);
• /* enable debug interrupts */
• irq_mask |= HDLCD_DEBUG_INT_MASK;
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, irq_mask);

+#endif +}

+static int hdlcd_irq_install(struct drm_device *dev, int irq)

It is inconsistent that the drm_device * is named "dev", as similar functions in this patch uses the name "drm".

...

+{

• int ret;
• if (irq == IRQ_NOTCONNECTED)

• return -ENOTCONN;
  

The code above is almost redundandt as request_irq has the same check. The only benefit of this check is that we avoid calling hdlcd_irq_preinstall().

I'd expect that there's a reason that the code is in _preinstall(). So testing for IRQF_NOTCONNECTED in request_irq() might be too late. I'd really like to here from driver maintainers that this can be changed.

I agree that the logic is duplicated and the whole thing could be simpler. But I rather stick with the original logic as used in drm_irq_install(). That function get's it totally wrong BTW.

And IRQ_NOTCONNECTED is only set for PCI devices which this is not.

Is that guaranteed?

Best regards Thomas

So I would thing the if () should be dropped here. ??

With the inputs considered/addressed: Acked-by: Sam Ravnborg sam@ravnborg.org

...

• hdlcd_irq_preinstall(dev);
• ret = request_irq(irq, hdlcd_irq, 0, dev->driver->name, dev);
• if (ret)

• return ret;
  

• hdlcd_irq_postinstall(dev);
• return 0;

+}

+static void hdlcd_irq_uninstall(struct drm_device *drm) +{

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• /* disable all the interrupts that we might have enabled */
• unsigned long irq_mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);

+#ifdef CONFIG_DEBUG_FS

• /* disable debug interrupts */
• irq_mask &= ~HDLCD_DEBUG_INT_MASK;

+#endif

• /* disable vsync interrupts */
• irq_mask &= ~HDLCD_INTERRUPT_VSYNC;
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, irq_mask);
• free_irq(hdlcd->irq, drm);

+}

• static int hdlcd_load(struct drm_device *drm, unsigned long flags) { struct hdlcd_drm_private *hdlcd = drm->dev_private;

@@ -90,7 +177,12 @@ static int hdlcd_load(struct drm_device *drm, unsigned long flags) goto setup_fail; }

• ret = drm_irq_install(drm, platform_get_irq(pdev, 0));

• ret = platform_get_irq(pdev, 0);
• if (ret < 0)

• goto irq_fail;
  

• hdlcd->irq = ret;
• ret = hdlcd_irq_install(drm, hdlcd->irq); if (ret < 0) { DRM_ERROR("failed to install IRQ handler\n"); goto irq_fail;

@@ -122,76 +214,6 @@ static void hdlcd_setup_mode_config(struct drm_device *drm) drm->mode_config.funcs = &hdlcd_mode_config_funcs; }

-static irqreturn_t hdlcd_irq(int irq, void *arg) -{

• struct drm_device *drm = arg;
• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• unsigned long irq_status;
• irq_status = hdlcd_read(hdlcd, HDLCD_REG_INT_STATUS);

-#ifdef CONFIG_DEBUG_FS

• if (irq_status & HDLCD_INTERRUPT_UNDERRUN)

• atomic_inc(&hdlcd->buffer_underrun_count);
  

• if (irq_status & HDLCD_INTERRUPT_DMA_END)

• atomic_inc(&hdlcd->dma_end_count);
  

• if (irq_status & HDLCD_INTERRUPT_BUS_ERROR)

• atomic_inc(&hdlcd->bus_error_count);
  

• if (irq_status & HDLCD_INTERRUPT_VSYNC)

• atomic_inc(&hdlcd->vsync_count);
  

-#endif

• if (irq_status & HDLCD_INTERRUPT_VSYNC)

• drm_crtc_handle_vblank(&hdlcd->crtc);
  

• /* acknowledge interrupt(s) */
• hdlcd_write(hdlcd, HDLCD_REG_INT_CLEAR, irq_status);
• return IRQ_HANDLED;

-}

-static void hdlcd_irq_preinstall(struct drm_device *drm) -{

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• /* Ensure interrupts are disabled */
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, 0);
• hdlcd_write(hdlcd, HDLCD_REG_INT_CLEAR, ~0);

-}

-static int hdlcd_irq_postinstall(struct drm_device *drm) -{ -#ifdef CONFIG_DEBUG_FS

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• unsigned long irq_mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);
• /* enable debug interrupts */
• irq_mask |= HDLCD_DEBUG_INT_MASK;
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, irq_mask);

-#endif

• return 0;

-}

-static void hdlcd_irq_uninstall(struct drm_device *drm) -{

• struct hdlcd_drm_private *hdlcd = drm->dev_private;
• /* disable all the interrupts that we might have enabled */
• unsigned long irq_mask = hdlcd_read(hdlcd, HDLCD_REG_INT_MASK);

-#ifdef CONFIG_DEBUG_FS

• /* disable debug interrupts */
• irq_mask &= ~HDLCD_DEBUG_INT_MASK;

-#endif

• /* disable vsync interrupts */
• irq_mask &= ~HDLCD_INTERRUPT_VSYNC;
• hdlcd_write(hdlcd, HDLCD_REG_INT_MASK, irq_mask);

-}

• #ifdef CONFIG_DEBUG_FS static int hdlcd_show_underrun_count(struct seq_file *m, void *arg) {

@@ -236,10 +258,6 @@ DEFINE_DRM_GEM_CMA_FOPS(fops);

static const struct drm_driver hdlcd_driver = { .driver_features = DRIVER_GEM | DRIVER_MODESET | DRIVER_ATOMIC,

• .irq_handler = hdlcd_irq,
• .irq_preinstall = hdlcd_irq_preinstall,
• .irq_postinstall = hdlcd_irq_postinstall,
• .irq_uninstall = hdlcd_irq_uninstall, DRM_GEM_CMA_DRIVER_OPS, #ifdef CONFIG_DEBUG_FS .debugfs_init = hdlcd_debugfs_init,

@@ -316,7 +334,7 @@ static int hdlcd_drm_bind(struct device *dev) err_unload: of_node_put(hdlcd->crtc.port); hdlcd->crtc.port = NULL;

• drm_irq_uninstall(drm);

• hdlcd_irq_uninstall(drm); of_reserved_mem_device_release(drm->dev); err_free: drm_mode_config_cleanup(drm);

@@ -338,7 +356,7 @@ static void hdlcd_drm_unbind(struct device *dev) hdlcd->crtc.port = NULL; pm_runtime_get_sync(dev); drm_atomic_helper_shutdown(drm);

• drm_irq_uninstall(drm);

• hdlcd_irq_uninstall(drm); pm_runtime_put(dev); if (pm_runtime_enabled(dev)) pm_runtime_disable(dev);

diff --git a/drivers/gpu/drm/arm/hdlcd_drv.h b/drivers/gpu/drm/arm/hdlcd_drv.h index fd438d177b64..909c39c28487 100644 --- a/drivers/gpu/drm/arm/hdlcd_drv.h +++ b/drivers/gpu/drm/arm/hdlcd_drv.h @@ -11,6 +11,7 @@ struct hdlcd_drm_private { struct clk *clk; struct drm_crtc crtc; struct drm_plane *plane;

• unsigned int irq; #ifdef CONFIG_DEBUG_FS atomic_t buffer_underrun_count; atomic_t bus_error_count;

-- 2.32.0