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fbdev: sh_mobile_hdmi: implement locking

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The SH-Mobile HDMI driver runs in several contexts: ISR, delayed work-queue,
task context, when called from the sh_mobile_lcdc framebuffer driver. This
creates ample race possibilities. Even though most these races are purely
theoretical, it is better to close them. To trace fb_info validity we install a
notification callback in the HDMI driver, and the only way for it to get to
driver internal data is by using struct sh_mobile_lcdc_chan, therefore it had
to be extracted into a separate common header.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Guennadi Liakhovetski
2010-09-03 07:20:23 +00:00
committed by Paul Mundt
parent 89712699d7
commit 6de9edd5bd
4 changed files with 141 additions and 47 deletions
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103
drivers/video/sh_mobile_hdmi.c
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@@ -26,6 +26,8 @@
#include <video/sh_mobile_hdmi.h>
#include <video/sh_mobile_lcdc.h>
#include "sh_mobile_lcdcfb.h"
#define HDMI_SYSTEM_CTRL 0x00 /* System control */
#define HDMI_L_R_DATA_SWAP_CTRL_RPKT 0x01 /* L/R data swap control,
bits 19..16 of 20-bit N for Audio Clock Regeneration packet */
@@ -209,6 +211,7 @@ struct sh_hdmi {
struct clk *hdmi_clk;
struct device *dev;
struct fb_info *info;
struct mutex mutex; /* Protect the info pointer */
struct delayed_work edid_work;
struct fb_var_screeninfo var;
};
@@ -720,17 +723,21 @@ static irqreturn_t sh_hdmi_hotplug(int irq, void *dev_id)
return IRQ_HANDLED;
}
/* locking: called with info->lock held, or before register_framebuffer() */
static void hdmi_display_on(void *arg, struct fb_info *info)
{
/*
* info is guaranteed to be valid, when we are called, because our
* FB_EVENT_FB_UNBIND notify is also called with info->lock held
*/
struct sh_hdmi *hdmi = arg;
struct sh_mobile_hdmi_info *pdata = hdmi->dev->platform_data;
pr_debug("%s(%p): state %x\n", __func__, pdata->lcd_dev, info->state);
/*
* FIXME: not a good place to store fb_info. And we cannot nullify it
* even on monitor disconnect. What should the lifecycle be?
*/
/* No need to lock */
hdmi->info = info;
switch (hdmi->hp_state) {
case HDMI_HOTPLUG_EDID_DONE:
/* PS mode d->e. All functions are active */
@@ -744,6 +751,7 @@ static void hdmi_display_on(void *arg, struct fb_info *info)
}
}
/* locking: called with info->lock held */
static void hdmi_display_off(void *arg)
{
struct sh_hdmi *hdmi = arg;
@@ -766,6 +774,8 @@ static void edid_work_fn(struct work_struct *work)
if (!pdata->lcd_dev)
return;
mutex_lock(&hdmi->mutex);
if (hdmi->hp_state == HDMI_HOTPLUG_EDID_DONE) {
pm_runtime_get_sync(hdmi->dev);
/* A device has been plugged in */
@@ -776,21 +786,25 @@ static void edid_work_fn(struct work_struct *work)
msleep(10);
if (!hdmi->info)
return;
goto out;
acquire_console_sem();
/* HDMI plug in */
hdmi->info->var = hdmi->var;
if (hdmi->info->state != FBINFO_STATE_RUNNING)
if (hdmi->info->state != FBINFO_STATE_RUNNING) {
fb_set_suspend(hdmi->info, 0);
else
hdmi_display_on(hdmi, hdmi->info);
} else {
if (lock_fb_info(hdmi->info)) {
hdmi_display_on(hdmi, hdmi->info);
unlock_fb_info(hdmi->info);
}
}
release_console_sem();
} else {
if (!hdmi->info)
return;
goto out;
acquire_console_sem();
@@ -801,13 +815,61 @@ static void edid_work_fn(struct work_struct *work)
pm_runtime_put(hdmi->dev);
}
out:
mutex_unlock(&hdmi->mutex);
pr_debug("%s(%p): end\n", __func__, pdata->lcd_dev);
}
static int sh_hdmi_notify(struct notifier_block *nb,
unsigned long action, void *data);
static struct notifier_block sh_hdmi_notifier = {
.notifier_call = sh_hdmi_notify,
};
static int sh_hdmi_notify(struct notifier_block *nb,
unsigned long action, void *data)
{
struct fb_event *event = data;
struct fb_info *info = event->info;
struct sh_mobile_lcdc_chan *ch = info->par;
struct sh_mobile_lcdc_board_cfg *board_cfg = &ch->cfg.board_cfg;
struct sh_hdmi *hdmi = board_cfg->board_data;
if (nb != &sh_hdmi_notifier || !hdmi || hdmi->info != info)
return NOTIFY_DONE;
switch(action) {
case FB_EVENT_FB_REGISTERED:
/* Unneeded, activation taken care by hdmi_display_on() */
break;
case FB_EVENT_FB_UNREGISTERED:
/*
* We are called from unregister_framebuffer() with the
* info->lock held. This is bad for us, because we can race with
* the scheduled work, which has to call fb_set_suspend(), which
* takes info->lock internally, so, edid_work_fn() cannot take
* and hold info->lock for the whole function duration. Using an
* additional lock creates a classical AB-BA lock up. Therefore,
* we have to release the info->lock temporarily, synchronise
* with the work queue and re-acquire the info->lock.
*/
unlock_fb_info(hdmi->info);
mutex_lock(&hdmi->mutex);
hdmi->info = NULL;
mutex_unlock(&hdmi->mutex);
lock_fb_info(hdmi->info);
return NOTIFY_OK;
}
return NOTIFY_DONE;
}
static int __init sh_hdmi_probe(struct platform_device *pdev)
{
struct sh_mobile_hdmi_info *pdata = pdev->dev.platform_data;
struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
struct sh_mobile_lcdc_board_cfg *board_cfg;
int irq = platform_get_irq(pdev, 0), ret;
struct sh_hdmi *hdmi;
long rate;
@@ -821,6 +883,7 @@ static int __init sh_hdmi_probe(struct platform_device *pdev)
return -ENOMEM;
}
mutex_init(&hdmi->mutex);
hdmi->dev = &pdev->dev;
hdmi->hdmi_clk = clk_get(&pdev->dev, "ick");
@@ -878,9 +941,11 @@ static int __init sh_hdmi_probe(struct platform_device *pdev)
#endif
/* Set up LCDC callbacks */
pdata->lcd_chan->board_cfg.board_data = hdmi;
pdata->lcd_chan->board_cfg.display_on = hdmi_display_on;
pdata->lcd_chan->board_cfg.display_off = hdmi_display_off;
board_cfg = &pdata->lcd_chan->board_cfg;
board_cfg->owner = THIS_MODULE;
board_cfg->board_data = hdmi;
board_cfg->display_on = hdmi_display_on;
board_cfg->display_off = hdmi_display_off;
INIT_DELAYED_WORK(&hdmi->edid_work, edid_work_fn);
@@ -907,6 +972,7 @@ eclkenable:
erate:
clk_put(hdmi->hdmi_clk);
egetclk:
mutex_destroy(&hdmi->mutex);
kfree(hdmi);
return ret;
@@ -917,19 +983,24 @@ static int __exit sh_hdmi_remove(struct platform_device *pdev)
struct sh_mobile_hdmi_info *pdata = pdev->dev.platform_data;
struct sh_hdmi *hdmi = platform_get_drvdata(pdev);
struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
struct sh_mobile_lcdc_board_cfg *board_cfg = &pdata->lcd_chan->board_cfg;
int irq = platform_get_irq(pdev, 0);
pdata->lcd_chan->board_cfg.display_on = NULL;
pdata->lcd_chan->board_cfg.display_off = NULL;
pdata->lcd_chan->board_cfg.board_data = NULL;
board_cfg->display_on = NULL;
board_cfg->display_off = NULL;
board_cfg->board_data = NULL;
board_cfg->owner = NULL;
/* No new work will be scheduled, wait for running ISR */
free_irq(irq, hdmi);
pm_runtime_disable(&pdev->dev);
/* Wait for already scheduled work */
cancel_delayed_work_sync(&hdmi->edid_work);
pm_runtime_disable(&pdev->dev);
clk_disable(hdmi->hdmi_clk);
clk_put(hdmi->hdmi_clk);
iounmap(hdmi->base);
release_mem_region(res->start, resource_size(res));
mutex_destroy(&hdmi->mutex);
kfree(hdmi);
return 0;