Re: [PATCH 5/5] drm/i915: l3 parity sysfs interface

Jesse Barnes
2012-05-25T17:51:24Z

On Fri, 27 Apr 2012 17:40:21 -0700
Ben Widawsky <ben@bwidawsk.net> wrote:

> Dumb binary interfaces which allow root-only updates of the cache
> remapping registers. As mentioned in a previous patch, software using
> this interface needs to know about HW limits, and other programming
> considerations as the kernel interface does no checking for these things
> on the root-only interface.
>
> v1: Drop extra posting reads (Chris)
> Return negative values in the sysfs interfaces on errors (Chris)
>
> Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
> ---
> drivers/gpu/drm/i915/i915_sysfs.c | 128 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 126 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_sysfs.c b/drivers/gpu/drm/i915/i915_sysfs.c
> index 79f8344..ed77cbf 100644
> --- a/drivers/gpu/drm/i915/i915_sysfs.c
> +++ b/drivers/gpu/drm/i915/i915_sysfs.c
> @@ -29,6 +29,7 @@
> #include <linux/module.h>
> #include <linux/stat.h>
> #include <linux/sysfs.h>
> +#include "intel_drv.h"
> #include "i915_drv.h"
>
> static u32 calc_residency(struct drm_device *dev, const u32 reg)
> @@ -92,20 +93,143 @@ static struct attribute_group rc6_attr_group = {
> .attrs = rc6_attrs
> };
>
> +static int l3_access_valid(struct drm_device *dev, loff_t offset)
> +{
> + if (!IS_IVYBRIDGE(dev))
> + return -EPERM;

-ENODEV?

> +
> + if (offset % 4 != 0)
> + return -EPERM;

-EINVAL?

> +
> + if (offset >= GEN7_L3LOG_SIZE)
> + return -ENXIO;

-E2BIG or -ERANGE?

And maybe some debug messages here so people can debug their daemons in
case some of the return values are identical.

> +
> + return 0;
> +}
> +
> +static ssize_t
> +i915_l3_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *attr, char *buf,
> + loff_t offset, size_t count)
> +{
> + struct device *dev = container_of(kobj, struct device, kobj);
> + struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> + struct drm_device *drm_dev = dminor->dev;
> + struct drm_i915_private *dev_priv = drm_dev->dev_private;
> + uint32_t misccpctl;
> + int i, ret;
> +
> + ret = l3_access_valid(drm_dev, offset);
> + if (ret)
> + return ret;
> +
> + ret = i915_mutex_lock_interruptible(drm_dev);
> + if (ret)
> + return ret;
> +
> + misccpctl = I915_READ(GEN7_MISCCPCTL);
> + I915_WRITE(GEN7_MISCCPCTL, misccpctl & ~GEN7_DOP_CLOCK_GATE_ENABLE);
> +
> + for (i = offset; count >= 4 && i < GEN7_L3LOG_SIZE; i += 4, count -= 4)
> + *((uint32_t *)(&buf[i])) = I915_READ(GEN7_L3LOG_BASE + i);
> +
> + I915_WRITE(GEN7_MISCCPCTL, misccpctl);
> +
> + mutex_unlock(&drm_dev->struct_mutex);
> +
> + return i - offset;
> +}
> +
> +static ssize_t
> +i915_l3_write(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *attr, char *buf,
> + loff_t offset, size_t count)
> +{
> + struct device *dev = container_of(kobj, struct device, kobj);
> + struct drm_minor *dminor = container_of(dev, struct drm_minor, kdev);
> + struct drm_device *drm_dev = dminor->dev;
> + struct drm_i915_private *dev_priv = drm_dev->dev_private;
> + u32 *temp = NULL;
> + int i, ret;
> +
> + ret = l3_access_valid(drm_dev, offset);
> + if (ret)
> + return ret;
> +
> + ret = i915_mutex_lock_interruptible(drm_dev);
> + if (ret)
> + return ret;
> +
> + if (!dev_priv->mm.l3_remap_info) {
> + temp = kzalloc(GEN7_L3LOG_SIZE, GFP_KERNEL);
> + if (!temp) {
> + mutex_unlock(&drm_dev->struct_mutex);
> + return -ENOMEM;
> + }
> + }

Grumble, lazy allocation. But if we did this at driver load time we'd
also need a valid bit so we knew whether to try to load it or not...

> +
> + ret = i915_gpu_idle(drm_dev, true);
> + if (ret) {
> + kfree(temp);
> + mutex_unlock(&drm_dev->struct_mutex);
> + return ret;
> + }
> +
> + /* TODO: Ideally we really want a GPU reset here to make sure errors
> + * aren't propagated Since I cannot find a stable way to reset the GPU
> + * at this point it is left as a TODO.
> + */

Do we want a reset? Or just to restart the app that consumed the
error? If the latter, then the current uevent ought to be enough,
potentially with a configurable SIGBUS or something.

> +
> + if (dev_priv->mm.l3_remap_info)
> + temp = dev_priv->mm.l3_remap_info;
> +
> + dev_priv->mm.l3_remap_info = temp;

I'd combine these assignments with the kzalloc block above just to keep
things together.

> +
> + for (i = offset; count >= 4 && i < GEN7_L3LOG_SIZE; i += 4, count -= 4) {
> + u32 remap = I915_READ(GEN7_L3LOG_BASE + i);
> + if (remap && remap != *temp)
> + DRM_ERROR("0x%x was already programmed to %x\n",
> + GEN7_L3LOG_BASE + i, remap);
> + *temp++ = *(uint32_t *)(&buf[i]);
> + }

Is this an error? Or just a "userspace is schizo" and therefore
just a DEBUG?

> +
> + i915_gem_l3_remap(drm_dev);

You could add the warning/debug info to l3_remap instead, right?

> +
> + mutex_unlock(&drm_dev->struct_mutex);
> +
> + return offset - i;
> +}
> +
> +static struct bin_attribute dpf_attrs = {
> + .attr = {.name = "l3_parity", .mode = (S_IRUSR | S_IWUSR)},
> + .size = GEN7_L3LOG_SIZE,
> + .read = i915_l3_read,
> + .write = i915_l3_write,
> + .mmap = NULL
> +};
> +
> void i915_setup_sysfs(struct drm_device *dev)
> {
> int ret;
>
> - /* ILK doesn't have any residency information */
> + /* ILK and below don't yet have relevant sysfs files */
> if (INTEL_INFO(dev)->gen < 6)
> return;
>
> ret = sysfs_merge_group(&dev->primary->kdev.kobj, &rc6_attr_group);
> if (ret)
> - DRM_ERROR("sysfs setup failed\n");
> + DRM_ERROR("RC6 residency sysfs setup failed\n");
> +
> + if (!IS_IVYBRIDGE(dev))
> + return;
> +
> + ret = device_create_bin_file(&dev->primary->kdev, &dpf_attrs);
> + if (ret)
> + DRM_ERROR("l3 parity sysfs setup failed\n");
> }
>
> void i915_teardown_sysfs(struct drm_device *dev)
> {
> + device_remove_bin_file(&dev->primary->kdev, &dpf_attrs);
> sysfs_unmerge_group(&dev->primary->kdev.kobj, &rc6_attr_group);
> }

I think Daniel covered the above.

With the above addressed:
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

--
Jesse Barnes, Intel Open Source Technology Center