lkml.org 
[lkml]   [2015]   [Apr]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] [media] ivtv: use arch_phys_wc_add() and require PAT disabled
From
Date
Hi Luis,

Sorry for the late reply.

Thank you for the patch! See my comments below:

On Wed, 2015-04-22 at 12:33 -0700, Luis R. Rodriguez wrote:
> From: "Luis R. Rodriguez" <mcgrof@suse.com>
>
> We are burrying direct access to MTRR code support on
> x86 in order to take advantage of PAT. In the future we
> also want to make the default behaviour of ioremap_nocache()
> to use strong UC, use of mtrr_add() on those systems
> would make write-combining void.
>
> In order to help both enable us to later make strong
> UC default and in order to phase out direct MTRR access
> code port the driver over to arch_phys_wc_add() and
> annotate that the device driver requires systems to
> boot with PAT disabled, with the nopat kernel parameter.
>
> This is a worthy comprmise given that the hardware is
> really rare these days,

I'm OK with the compromise solution. It makes sense.

> and perhaps only some lost souls
> in some third world country are expected to be using this
> feature of the device driver.
>
> Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Andy Walls <awalls@md.metrocast.net>
> Cc: Suresh Siddha <sbsiddha@gmail.com>
> Cc: Ingo Molnar <mingo@elte.hu>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Juergen Gross <jgross@suse.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Dave Airlie <airlied@redhat.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: Antonino Daplas <adaplas@gmail.com>
> Cc: Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>
> Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: Stefan Bader <stefan.bader@canonical.com>
> Cc: Ville Syrjälä <syrjala@sci.fi>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: Davidlohr Bueso <dbueso@suse.de>
> Cc: konrad.wilk@oracle.com
> Cc: ville.syrjala@linux.intel.com
> Cc: david.vrabel@citrix.com
> Cc: jbeulich@suse.com
> Cc: toshi.kani@hp.com
> Cc: Roger Pau Monné <roger.pau@citrix.com>
> Cc: linux-fbdev@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Cc: ivtv-devel@ivtvdriver.org
> Cc: linux-media@vger.kernel.org
> Cc: xen-devel@lists.xensource.com
> Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
> ---
> drivers/media/pci/ivtv/Kconfig | 3 +++
> drivers/media/pci/ivtv/ivtvfb.c | 59 +++++++++++++++++------------------------
> 2 files changed, 27 insertions(+), 35 deletions(-)
>
> diff --git a/drivers/media/pci/ivtv/Kconfig b/drivers/media/pci/ivtv/Kconfig
> index dd6ee57e..b2a7f88 100644
> --- a/drivers/media/pci/ivtv/Kconfig
> +++ b/drivers/media/pci/ivtv/Kconfig
> @@ -57,5 +57,8 @@ config VIDEO_FB_IVTV
> This is used in the Hauppauge PVR-350 card. There is a driver
> homepage at <http://www.ivtvdriver.org>.
>
> + If you have this hardware you will need to boot with PAT disabled
> + on your x86 systems, use the nopat kernel parameter.
> +
> To compile this driver as a module, choose M here: the
> module will be called ivtvfb.
> diff --git a/drivers/media/pci/ivtv/ivtvfb.c b/drivers/media/pci/ivtv/ivtvfb.c
> index 9ff1230..552408b 100644
> --- a/drivers/media/pci/ivtv/ivtvfb.c
> +++ b/drivers/media/pci/ivtv/ivtvfb.c
> @@ -44,8 +44,8 @@
> #include <linux/ivtvfb.h>
> #include <linux/slab.h>
>
> -#ifdef CONFIG_MTRR
> -#include <asm/mtrr.h>
> +#ifdef CONFIG_X86_64
> +#include <asm/pat.h>
> #endif
>
> #include "ivtv-driver.h"
> @@ -155,12 +155,11 @@ struct osd_info {
> /* Buffer size */
> u32 video_buffer_size;
>
> -#ifdef CONFIG_MTRR
> /* video_base rounded down as required by hardware MTRRs */
> unsigned long fb_start_aligned_physaddr;
> /* video_base rounded up as required by hardware MTRRs */
> unsigned long fb_end_aligned_physaddr;
> -#endif
> + int wc_cookie;
>
> /* Store the buffer offset */
> int set_osd_coords_x;
> @@ -1099,6 +1098,8 @@ static int ivtvfb_init_vidmode(struct ivtv *itv)
> static int ivtvfb_init_io(struct ivtv *itv)
> {
> struct osd_info *oi = itv->osd_info;
> + /* Find the largest power of two that maps the whole buffer */
> + int size_shift = 31;
>
> mutex_lock(&itv->serialize_lock);
> if (ivtv_init_on_first_open(itv)) {
> @@ -1120,6 +1121,7 @@ static int ivtvfb_init_io(struct ivtv *itv)
> oi->video_buffer_size = 1704960;
>
> oi->video_pbase = itv->base_addr + IVTV_DECODER_OFFSET + oi->video_rbase;
> + /* XXX: split this for PAT */

Please remove this comment. It is prescriptive of a particular
solution, and probably not the one I'm going to implement. The ivtv
main driver alreay splits the encoder, decoder, and register regions
into 3 mappings. The final solution will set the whole 8 MB decoder
region mapping to WC, and then fix up all calls in the ivtvfb and ivtv
drivers where writes to the decoder memory with WC enabled could be a
problem.

Also many other places in the driver need audit in a conversion to work
with PAT, so no need to call out this one location with a comment.

> oi->video_vbase = itv->dec_mem + oi->video_rbase;
>
> if (!oi->video_vbase) {
> @@ -1132,29 +1134,16 @@ static int ivtvfb_init_io(struct ivtv *itv)
> oi->video_pbase, oi->video_vbase,
> oi->video_buffer_size / 1024);
>
> -#ifdef CONFIG_MTRR
> - {
> - /* Find the largest power of two that maps the whole buffer */
> - int size_shift = 31;
> -
> - while (!(oi->video_buffer_size & (1 << size_shift))) {
> - size_shift--;
> - }
> - size_shift++;
> - oi->fb_start_aligned_physaddr = oi->video_pbase & ~((1 << size_shift) - 1);
> - oi->fb_end_aligned_physaddr = oi->video_pbase + oi->video_buffer_size;
> - oi->fb_end_aligned_physaddr += (1 << size_shift) - 1;
> - oi->fb_end_aligned_physaddr &= ~((1 << size_shift) - 1);
> - if (mtrr_add(oi->fb_start_aligned_physaddr,
> - oi->fb_end_aligned_physaddr - oi->fb_start_aligned_physaddr,
> - MTRR_TYPE_WRCOMB, 1) < 0) {
> - IVTVFB_INFO("disabled mttr\n");
> - oi->fb_start_aligned_physaddr = 0;
> - oi->fb_end_aligned_physaddr = 0;
> - }
> - }
> -#endif
> -
> + while (!(oi->video_buffer_size & (1 << size_shift)))
> + size_shift--;
> + size_shift++;
> + oi->fb_start_aligned_physaddr = oi->video_pbase & ~((1 << size_shift) - 1);
> + oi->fb_end_aligned_physaddr = oi->video_pbase + oi->video_buffer_size;
> + oi->fb_end_aligned_physaddr += (1 << size_shift) - 1;
> + oi->fb_end_aligned_physaddr &= ~((1 << size_shift) - 1);
> + oi->wc_cookie = arch_phys_wc_add(oi->fb_start_aligned_physaddr,
> + oi->fb_end_aligned_physaddr -
> + oi->fb_start_aligned_physaddr);
> /* Blank the entire osd. */
> memset_io(oi->video_vbase, 0, oi->video_buffer_size);
>
> @@ -1172,14 +1161,7 @@ static void ivtvfb_release_buffers (struct ivtv *itv)
>
> /* Release pseudo palette */
> kfree(oi->ivtvfb_info.pseudo_palette);
> -
> -#ifdef CONFIG_MTRR
> - if (oi->fb_end_aligned_physaddr) {
> - mtrr_del(-1, oi->fb_start_aligned_physaddr,
> - oi->fb_end_aligned_physaddr - oi->fb_start_aligned_physaddr);
> - }
> -#endif
> -
> + arch_phys_wc_del(oi->wc_cookie);
> kfree(oi);
> itv->osd_info = NULL;
> }
> @@ -1190,6 +1172,13 @@ static int ivtvfb_init_card(struct ivtv *itv)
> {
> int rc;
>
> +#ifdef CONFIG_X86_64
> + if (WARN(pat_enabled,

This check might be better placed in ivtvfb_init(). This check is going
to have the same result for every PVR-350 card in the system that is
found by ivtvfb.

> + "ivtv needs PAT disabled, boot with nopat kernel parameter\n")) {

This needs to read "ivtvfb needs [...]" to avoid user confusion with the
main ivtv driver module.

This change is the only one I really care about. Then I can give my
Ack.

Regards,
Andy

> + return EINVAL;
> + }
> +#endif
> +
> if (itv->osd_info) {
> IVTVFB_ERR("Card %d already initialised\n", ivtvfb_card_id);
> return -EBUSY;




\
 
 \ /
  Last update: 2015-04-25 14:21    [W:0.082 / U:0.108 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site