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    SubjectRe: [Intel-gfx] Major 2.6.38 / 2.6.39 / 3.0 regression ignored?
    On Tue, Jul 26, 2011 at 05:48:27PM +0400, Kirill Smelkov wrote:
    > On Sat, Jul 23, 2011 at 12:23:36AM +0400, Kirill Smelkov wrote:
    > > Keith,
    > >
    > > first of all thanks for your prompt reply. Then...
    > >
    > > On Fri, Jul 22, 2011 at 11:00:41AM -0700, Keith Packard wrote:
    > > > On Fri, 22 Jul 2011 15:08:06 +0400, Kirill Smelkov <kirr@mns.spb.ru> wrote:
    > > >
    > > > > And now after v3.0 is out, I've tested it again, and yes, like it was
    > > > > broken on v3.0-rc5, it is (now even more) broken on v3.0 -- after first
    > > > > bad io access the system freezes completely:
    > > >
    > > > I looked at this when I first saw it (a couple of weeks ago), and I
    > > > couldn't see any obvious reason this patch would cause this particular
    > > > problem. I didn't want to revert the patch at that point as I feared it
    > > > would cause other subtle problems. Given that you've got a work-around,
    > > > it seemed best to just push this off past 3.0.
    > >
    > > What kind of a workaround are you talking about? Sorry, to me it all
    > > looked like "UMS is being ignored forever". Anyway, let's move on to try
    > > to solve the issue.
    > >
    > >
    > > > Given the failing address passed to ioread32, this seems like it's
    > > > probably the call to READ_BREADCRUMB -- I915_BREADCRUMB_INDEX is 0x21,
    > > > which is an offset in 32-bit units within the hardware status page. If
    > > > the status_page.page_addr value was zero, then the computed address
    > > > would end up being 0x84.
    > > >
    > > > And, it looks like status_page.page_addr *will* end up being zero as a
    > > > result of the patch in question. The patch resets the entire ring
    > > > structure contents back to the initial values, which includes smashing
    > > > the status_page structure to zero, clearing the value of
    > > > status_page.page_addr set in i915_init_phys_hws.
    > > >
    > > > Here's an untested patch which moves the initialization of
    > > > status_page.page_addr into intel_render_ring_init_dri. I note that
    > > > intel_init_render_ring_buffer *already* has the setting of the
    > > > status_page.page_addr value, and so I've removed the setting of
    > > > status_page.page_addr from i915_init_phys_hws.
    > > >
    > > > I suspect we could remove the memset from intel_init_render_ring_buffer;
    > > > it seems entirely superfluous given the memset in i915_init_phys_hws.
    > > >
    > > > From 159ba1dd207fc52590ce8a3afd83f40bd2cedf46 Mon Sep 17 00:00:00 2001
    > > > From: Keith Packard <keithp@keithp.com>
    > > > Date: Fri, 22 Jul 2011 10:44:39 -0700
    > > > Subject: [PATCH] drm/i915: Initialize RCS ring status page address in
    > > > intel_render_ring_init_dri
    > > >
    > > > Physically-addressed hardware status pages are initialized early in
    > > > the driver load process by i915_init_phys_hws. For UMS environments,
    > > > the ring structure is not initialized until the X server starts. At
    > > > that point, the entire ring structure is re-initialized with all new
    > > > values. Any values set in the ring structure (including
    > > > ring->status_page.page_addr) will be lost when the ring is
    > > > re-initialized.
    > > >
    > > > This patch moves the initialization of the status_page.page_addr value
    > > > to intel_render_ring_init_dri.
    > > >
    > > > Signed-off-by: Keith Packard <keithp@keithp.com>
    > > > ---
    > > > drivers/gpu/drm/i915/i915_dma.c | 6 ++----
    > > > drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
    > > > 2 files changed, 5 insertions(+), 4 deletions(-)
    > > >
    > > > diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
    > > > index 1271282..8a3942c 100644
    > > > --- a/drivers/gpu/drm/i915/i915_dma.c
    > > > +++ b/drivers/gpu/drm/i915/i915_dma.c
    > > > @@ -61,7 +61,6 @@ static void i915_write_hws_pga(struct drm_device *dev)
    > > > static int i915_init_phys_hws(struct drm_device *dev)
    > > > {
    > > > drm_i915_private_t *dev_priv = dev->dev_private;
    > > > - struct intel_ring_buffer *ring = LP_RING(dev_priv);
    > > >
    > > > /* Program Hardware Status Page */
    > > > dev_priv->status_page_dmah =
    > > > @@ -71,10 +70,9 @@ static int i915_init_phys_hws(struct drm_device *dev)
    > > > DRM_ERROR("Can not allocate hardware status page\n");
    > > > return -ENOMEM;
    > > > }
    > > > - ring->status_page.page_addr =
    > > > - (void __force __iomem *)dev_priv->status_page_dmah->vaddr;
    > > >
    > > > - memset_io(ring->status_page.page_addr, 0, PAGE_SIZE);
    > > > + memset_io((void __force __iomem *)dev_priv->status_page_dmah->vaddr,
    > > > + 0, PAGE_SIZE);
    > > >
    > > > i915_write_hws_pga(dev);
    > > >
    > > > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > > index e961568..47b9b27 100644
    > > > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > > @@ -1321,6 +1321,9 @@ int intel_render_ring_init_dri(struct drm_device *dev, u64 start, u32 size)
    > > > ring->get_seqno = pc_render_get_seqno;
    > > > }
    > > >
    > > > + if (!I915_NEED_GFX_HWS(dev))
    > > > + ring->status_page.page_addr = dev_priv->status_page_dmah->vaddr;
    > > > +
    > > > ring->dev = dev;
    > > > INIT_LIST_HEAD(&ring->active_list);
    > > > INIT_LIST_HEAD(&ring->request_list);
    > >
    > > I can't tell whether this is correct, because intel gfx driver is
    > > unknown to me, but from the first glance your description sounds reasonable.
    > >
    > > I'm out of office till ~ next week's tuesday, and on return I'll try
    > > to test it on the hardware in question.
    >
    > Keith, thanks again for the patch. As promised I've tested it on the
    > hardware in question and yes, bad_access is gone and X seems to work,
    > so thank you, but...
    >
    >
    > I see there are more such bugs in introduced-in-guilty-patch
    > intel_render_ring_init_dri(). For example ring->irq_queue is
    > left uninitialized and also ring->irq_lock etc...
    >
    >
    > I'm X newbie, so if here is something stupid X-wise, please don't
    > beat me too hard, but to me the gist of the problem is the original
    > patch, where Chris does
    >
    > ( git show e8616b6ced6137085e6657cc63bc2fe3900b8616 )
    > > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > index 03e3370..51fbc5e 100644
    > > --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
    > > @@ -1291,6 +1291,48 @@ int intel_init_render_ring_buffer(struct drm_device *dev)
    > > return intel_init_ring_buffer(dev, ring);
    > > }
    > >
    > > +int intel_render_ring_init_dri(struct drm_device *dev, u64 start, u32 size)
    > > +{
    > > + drm_i915_private_t *dev_priv = dev->dev_private;
    > > + struct intel_ring_buffer *ring = &dev_priv->ring[RCS];
    > > +
    > > + *ring = render_ring;
    > ^^^^^^^^^^^^^^^^^^^
    > here resets
    >
    > > + if (INTEL_INFO(dev)->gen >= 6) {
    > > + ring->add_request = gen6_add_request;
    > > + ring->irq_get = gen6_render_ring_get_irq;
    > > + ring->irq_put = gen6_render_ring_put_irq;
    > > + } else if (IS_GEN5(dev)) {
    > > + ring->add_request = pc_render_add_request;
    > > + ring->get_seqno = pc_render_get_seqno;
    > > + }
    >
    > and then the rest of the `ring` is initialized seemingly copy-pasted
    > from intel_init_ring_buffer():
    >
    > > + ring->dev = dev;
    > > + INIT_LIST_HEAD(&ring->active_list);
    > > + INIT_LIST_HEAD(&ring->request_list);
    > > + INIT_LIST_HEAD(&ring->gpu_write_list);
    > > +
    > > + ring->size = size;
    > > + ring->effective_size = ring->size;
    > > + if (IS_I830(ring->dev))
    > > + ring->effective_size -= 128;
    > > +
    > > + ring->map.offset = start;
    > > + ring->map.size = size;
    > > + ring->map.type = 0;
    > > + ring->map.flags = 0;
    > > + ring->map.mtrr = 0;
    > ...
    >
    > where both 3 chunks go almost exactly from intel_init_ring_buffer(), and
    > ring->effective_size tweak even stripped original comment:
    >
    > # original version from intel_init_ring_buffer():
    > /* Workaround an erratum on the i830 which causes a hang if
    > * the TAIL pointer points to within the last 2 cachelines
    > * of the buffer.
    > */
    > ring->effective_size = ring->size;
    > if (IS_I830(ring->dev))
    > ring->effective_size -= 128;
    >
    > ...
    >
    >
    > The line marked "here resets" resets all the fields, and maybe it's not a good
    > idea to re-initialize them all afterwards (missing some as this thread show),
    > or at least if it is really needed, share initialization code between
    > intel_render_ring_init_dri() and intel_init_ring_buffer() ?
    >
    > >From the outside it looks like the offending patch was done as a quick
    > fix in a hurry (lots of copy-paste), and maybe it would be better to
    > re-do it properly...

    Silence... ?

    I read UMS is still ignored, because e.g. that uninitialized
    ring->irq_lock which I've wrote about above is for sure used e.g. in
    gen6_render_ring_get_irq() added to ring vtable in
    intel_render_ring_init_dri().

    And also is copy-pasting, instead of properly structuring things, ok?


    Why not revert what caused trouble and introduced other subtle bugs, and
    redo things properly in the first place?


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