[PATCH] High resolution timer for cx88 remotes

[AH <andrzej.hajda@xxxxx>]

Hi

Some remotes requires short polling interval which in modern kernels is 
below resolution of standard scheduler (schedule_delayed_work), this 
causes problem of missed keystrokes. One of the solutions is to raise 
kernel timer frequency, my proposition is to use high resolution timers 
which are present in kernel since 2.6.16 (at least API AFAIK).
I have encountered this problem on my Winfast 2000XP Expert, but after 
checking cx88-input.c it seems that following cards can be affected also:
WINFAST2000XP_EXPERT
WINFAST_DTV1000
WINFAST_TV2000_XP_GLOBAL
PROLINK_PLAYTVPVR
PIXELVIEW_PLAYTV_ULTRA_PRO
PROLINK_PV_8000GT
PROLINK_PV_GLOBAL_XTREME
KWORLD_LTV883
MSI_TVANYWHERE_MASTER

Patched driver seems to work on my system, with kernel 2.6.28.
I have removed kernel checks for versions below 2.6.20 - they were 
because of API changes in scheduler.

I have not tested it on older kernels.

Regards
AH

diff -r 315bc4b65b4f linux/drivers/media/video/cx88/cx88-input.c
--- a/linux/drivers/media/video/cx88/cx88-input.c       Sun May 17 
12:28:55 2009 +0000
+++ b/linux/drivers/media/video/cx88/cx88-input.c       Sat May 23 
14:04:17 2009 +0200
@@ -23,10 +23,10 @@
 */

#include <linux/init.h>
-#include <linux/delay.h>
#include <linux/input.h>
#include <linux/pci.h>
#include <linux/module.h>
+#include <linux/hrtimer.h>

#include "compat.h"
#include "cx88.h"
@@ -49,7 +49,7 @@

       /* poll external decoder */
       int polling;
-       struct delayed_work work;
+       struct hrtimer timer;
       u32 gpio_addr;
       u32 last_gpio;
       u32 mask_keycode;
@@ -144,31 +144,25 @@
       }
}

-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
-static void cx88_ir_work(void *data)
-#else
-static void cx88_ir_work(struct work_struct *work)
-#endif
+enum hrtimer_restart cx88_ir_work(struct hrtimer *timer)
{
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
-       struct cx88_IR *ir = data;
-#else
-       struct cx88_IR *ir = container_of(work, struct cx88_IR, work.work);
-#endif
+       unsigned long missed;
+       struct cx88_IR *ir = container_of(timer, struct cx88_IR, timer);

       cx88_ir_handle_key(ir);
-       schedule_delayed_work(&ir->work, msecs_to_jiffies(ir->polling));
+       missed = hrtimer_forward_now(&ir->timer, ktime_set(0, 
ir->polling * 1000000));
+       if (missed > 1)
+               ir_dprintk("Missed ticks %ld\n", missed - 1);
+
+       return HRTIMER_RESTART;
}

void cx88_ir_start(struct cx88_core *core, struct cx88_IR *ir)
{
       if (ir->polling) {
-#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,20)
-               INIT_DELAYED_WORK(&ir->work, cx88_ir_work, ir);
-#else
-               INIT_DELAYED_WORK(&ir->work, cx88_ir_work);
-#endif
-               schedule_delayed_work(&ir->work, 0);
+               hrtimer_init(&ir->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+               ir->timer.function = cx88_ir_work;
+               hrtimer_start(&ir->timer, ktime_set(0, ir->polling * 
1000000), HRTIMER_MODE_REL);
       }
       if (ir->sampling) {
               core->pci_irqmask |= PCI_INT_IR_SMPINT;
@@ -185,7 +179,7 @@
       }

       if (ir->polling)
-               cancel_delayed_work_sync(&ir->work);
+               hrtimer_cancel(&ir->timer);
}

/* 
---------------------------------------------------------------------- */

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