[PATCH v1 09/47] vidoe: fbdev: atyfb: remove and fix MTRR MMIO "hole" work around

Luis R. Rodriguez
2015-03-20T23:40:47Z

From: "Luis R. Rodriguez" <mcgrof@suse.com>

The atyfb driver uses an MTRR work around since some
cards use the same PCI BAR for the framebuffer and MMIO.
In such cards the last page is used for MMIO, the rest for
the framebuffer, so on those cards we ioremap() the MMIO
page alone, then again ioremap() the full framebuffer
including the MMIO space *and* ___then___ use an MTRR with
MTRR_TYPE_WRCOMB on the full PCI BAR... and finally "hole"
in an MTRR_TYPE_UNCACHABLE MTRR only for MMIO.

This is a terrible fucking work around, and should by no means
be necessary however evidence through a large series of conversion
of drivers to ioremap_wc() for the framebuffer shows that around
the time MTRR started becoming popular devices did not have things
lined up for easily separating the framebuffer and MMIO register
access. In some cases a driver requires significant intrusive
changes in order to make the split for an ioremap() for MMIO registers
and another ioremap_wc() for the framebuffer, at other times a
bit of careful study of the driver suffices. This example driver
falls into the later category.

We can replace the MTRR MTRR_TYPE_UNCACHABLE
work around by using ioremap_nocache(), the length of the
MMIO space should already be correct. The other part we
need to correct is ensuring we ioremap() for the framebuffer
only the required size. Since the ioremap() happens early
on probe for PCI devices before aty_init() where we typically
adjust the length and know how to do it, we can fix this by
pegging the bus type as PCI on PCI probe, and finally fudging
and framebuffer length just as we do on aty_init().

The last thing we do must do to remain sane is ensure we
use the info->fix.smem_start and info->fix.smem_len for
the framebuffer MTRR as we know that is always well adjusted.
The *one* concern here would be if the MTRR is not in units
of 4K __but__ we already know that in the PCI case this cannot
happen, in the shared space setting the MTRR would be up to
0x7ff000 and assuming a 4K page:

; 0x7ff000 / 0x1000
2047

Also, internally when MTRR is used mtrr_add() will use mtrr_check()
and that should splat a warning when the MTRR base and size are
not compatible with what is expected for MTRR usage.

This fix lets us nuke the MTRR_TYPE_UNCACHABLE MTRR "hole".

Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Juergen Gross <jgross@suse.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Antonino Daplas <adaplas@gmail.com>
Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-fbdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
---
drivers/video/fbdev/aty/atyfb.h | 1 -
drivers/video/fbdev/aty/atyfb_base.c | 28 ++++++----------------------
2 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/drivers/video/fbdev/aty/atyfb.h b/drivers/video/fbdev/aty/atyfb.h
index 1f39a62..89ec439 100644
--- a/drivers/video/fbdev/aty/atyfb.h
+++ b/drivers/video/fbdev/aty/atyfb.h
@@ -184,7 +184,6 @@ struct atyfb_par {
spinlock_t int_lock;
#ifdef CONFIG_MTRR
int mtrr_aper;
- int mtrr_reg;
#endif
u32 mem_cntl;
struct crtc saved_crtc;
diff --git a/drivers/video/fbdev/aty/atyfb_base.c b/drivers/video/fbdev/aty/atyfb_base.c
index 8025624..8875e56 100644
--- a/drivers/video/fbdev/aty/atyfb_base.c
+++ b/drivers/video/fbdev/aty/atyfb_base.c
@@ -2630,21 +2630,10 @@ static int aty_init(struct fb_info *info)

#ifdef CONFIG_MTRR
par->mtrr_aper = -1;
- par->mtrr_reg = -1;
if (!nomtrr) {
- /* Cover the whole resource. */
- par->mtrr_aper = mtrr_add(par->res_start, par->res_size,
+ par->mtrr_aper = mtrr_add(info->fix.smem_start,
+ info->fix.smem_len,
MTRR_TYPE_WRCOMB, 1);
- if (par->mtrr_aper >= 0 && !par->aux_start) {
- /* Make a hole for mmio. */
- par->mtrr_reg = mtrr_add(par->res_start + 0x800000 -
- GUI_RESERVE, GUI_RESERVE,
- MTRR_TYPE_UNCACHABLE, 1);
- if (par->mtrr_reg < 0) {
- mtrr_del(par->mtrr_aper, 0, 0);
- par->mtrr_aper = -1;
- }
- }
}
#endif

@@ -2776,10 +2765,6 @@ aty_init_exit:
par->pll_ops->set_pll(info, &par->saved_pll);

#ifdef CONFIG_MTRR
- if (par->mtrr_reg >= 0) {
- mtrr_del(par->mtrr_reg, 0, 0);
- par->mtrr_reg = -1;
- }
if (par->mtrr_aper >= 0) {
mtrr_del(par->mtrr_aper, 0, 0);
par->mtrr_aper = -1;
@@ -3466,7 +3451,7 @@ static int atyfb_setup_generic(struct pci_dev *pdev, struct fb_info *info,
}

info->fix.mmio_start = raddr;
- par->ati_regbase = ioremap(info->fix.mmio_start, 0x1000);
+ par->ati_regbase = ioremap_nocache(info->fix.mmio_start, 0x1000);
if (par->ati_regbase == NULL)
return -ENOMEM;

@@ -3491,6 +3476,8 @@ static int atyfb_setup_generic(struct pci_dev *pdev, struct fb_info *info,
info->fix.smem_start = addr;
info->fix.smem_len = 0x800000;

+ aty_fudge_framebuffer_len(info);
+
info->screen_base = ioremap(info->fix.smem_start, info->fix.smem_len);
if (info->screen_base == NULL) {
ret = -ENOMEM;
@@ -3563,6 +3550,7 @@ static int atyfb_pci_probe(struct pci_dev *pdev,
return -ENOMEM;
}
par = info->par;
+ par->bus_type = PCI;
info->fix = atyfb_fix;
info->device = &pdev->dev;
par->pci_id = pdev->device;
@@ -3732,10 +3720,6 @@ static void atyfb_remove(struct fb_info *info)
#endif

#ifdef CONFIG_MTRR
- if (par->mtrr_reg >= 0) {
- mtrr_del(par->mtrr_reg, 0, 0);
- par->mtrr_reg = -1;
- }
if (par->mtrr_aper >= 0) {
mtrr_del(par->mtrr_aper, 0, 0);
par->mtrr_aper = -1;
--
2.3.2.209.gd67f9d5.dirty