Commit 526daee7 authored by French, Nicholas A's avatar French, Nicholas A Committed by Mauro Carvalho Chehab
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media: ivtv: add parameter to enable ivtvfb on x86 PAT systems 



ivtvfb was previously disabled for x86 PAT-enabled systems
by commit 1bf1735b ("x86/mm/pat, drivers/media/ivtv:
Use arch_phys_wc_add() and require PAT disabled") as a
workaround to abstract MTRR code away from device drivers.

The driver is not easily upgradable to the PAT-aware
ioremap_wc() API since the firmware hides the address
ranges that should be marked write-combined from the driver.
However, since a write-combined cache on the framebuffer
is only a performance enhancement not a requirement for
the framebuffer to function, completely disabling the driver
in this configuration is not necessary.

Add force_pat module parameter and a corresponding kernel
configuration parameter to optionally force initialization
on PAT-enabled x86 systems with a warning about the lack of
write-combined caching, and document the reasons the driver
cannot be easily updated to support wc caching on all systems.

Signed-off-by: default avatarNick French <naf@ou.edu>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil-cisco@xs4all.nl: fix typo, split long pr_ lines up]
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+samsung@kernel.org>
parent dc60a4cf

drivers/media/pci/ivtv/Kconfig

+20 −3
Original line number Diff line number Diff line
@@ -70,8 +70,25 @@ config VIDEO_FB_IVTV 
	  This is used in the Hauppauge PVR-350 card. There is a driver

	  homepage at <http://www.ivtvdriver.org>.



	  In order to use this module, you will need to boot with PAT disabled

	  on x86 systems, using the nopat kernel parameter.



	  To compile this driver as a module, choose M here: the

	  module will be called ivtvfb.



config VIDEO_FB_IVTV_FORCE_PAT

	bool "force cx23415 framebuffer init with x86 PAT enabled"

	depends on VIDEO_FB_IVTV && X86_PAT

	default n

	---help---

	  With PAT enabled, the cx23415 framebuffer driver does not

	  utilize write-combined caching on the framebuffer memory.

	  For this reason, the driver will by default disable itself

	  when initializied on a kernel with PAT enabled (i.e. not

	  using the nopat kernel parameter).



	  The driver is not easily upgradable to the PAT-aware

	  ioremap_wc() API since the firmware hides the address

	  ranges that should be marked write-combined from the driver.



	  With this setting enabled, the framebuffer will initialize on

	  PAT-enabled systems but the framebuffer memory will be uncached.



	  If unsure, say N.

drivers/media/pci/ivtv/ivtvfb.c

+14 −2
Original line number Diff line number Diff line
@@ -55,6 +55,7 @@ 
/* card parameters */

static int ivtvfb_card_id = -1;

static int ivtvfb_debug = 0;

static bool ivtvfb_force_pat = IS_ENABLED(CONFIG_VIDEO_FB_IVTV_FORCE_PAT);

static bool osd_laced;

static int osd_depth;

static int osd_upper;
@@ -64,6 +65,7 @@ static int osd_xres; 


module_param(ivtvfb_card_id, int, 0444);

module_param_named(debug,ivtvfb_debug, int, 0644);

module_param_named(force_pat, ivtvfb_force_pat, bool, 0644);

module_param(osd_laced, bool, 0444);

module_param(osd_depth, int, 0444);

module_param(osd_upper, int, 0444);
@@ -79,6 +81,9 @@ MODULE_PARM_DESC(debug, 
		 "Debug level (bitmask). Default: errors only\n"

		 "\t\t\t(debug = 3 gives full debugging)");



MODULE_PARM_DESC(force_pat,

		 "Force initialization on x86 PAT-enabled systems (bool).\n");



/* Why upper, left, xres, yres, depth, laced ? To match terminology used

   by fbset.

   Why start at 1 for left & upper coordinate ? Because X doesn't allow 0 */
@@ -1167,9 +1172,16 @@ static int ivtvfb_init_card(struct ivtv *itv) 


#ifdef CONFIG_X86_64

	if (pat_enabled()) {

		pr_warn("ivtvfb needs PAT disabled, boot with nopat kernel parameter\n");

		if (ivtvfb_force_pat) {

			pr_info("PAT is enabled. Write-combined framebuffer caching will be disabled.\n");

			pr_info("To enable caching, boot with nopat kernel parameter\n");

		} else {

			pr_warn("ivtvfb needs PAT disabled for write-combined framebuffer caching.\n");

			pr_warn("Boot with nopat kernel parameter to use caching, or use the\n");

			pr_warn("force_pat module parameter to run with caching disabled\n");

			return -ENODEV;

		}

	}

#endif



	if (itv->osd_info) {

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