media: ivtv: add parameter to enable ivtvfb on x86 PAT systems
Subsystems (2)
PATCH v2 1/1 media: ivtv: add parameter to enable ivtvfb on x86 PAT systems
ivtvfb was previously disabled for x86 PAT-enabled systems by commit 1bf1735b4780 ("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.
---
Changes in v2:
- Add wording to Kconfig parameter to memorialize the reasoning this driver cannot easily be upgraded to use ioremap_wc()
drivers/media/pci/ivtv/Kconfig | 23 ++++++++++++++++++++--- drivers/media/pci/ivtv/ivtvfb.c | 19 +++++++++++++++++-- 2 files changed, 37 insertions(+), 5 deletions(-)
drivers/media/pci/ivtv/Kconfig +20 -3
@@ -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 frambuffer 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 +17 -2
@@ -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 */
@@ -1169,8 +1174,18 @@ 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" ); -return -ENODEV ; +if (ivtvfb_force_pat) { +pr_info ("PAT is enabled. Write-combined framebuffer " +"caching will be disabled. To enable caching, " +"boot with nopat kernel parameter\n" ); + }else { +pr_warn ("ivtvfb needs PAT disabled for write-combined " +"framebuffer caching. Boot with nopat kernel " +"parameter to use caching, or use the " +"force_pat module parameter to run with " +"caching disabled\n" ); +return -ENODEV ; + } }#endif
Signature · 1 line
2.13.6