From: "Ahmed S. Darwish" a.darwish@linutronix.de

alloc_req() uses in_interrupt() to detect if it is safe to use down().

The usage of in_interrupt() in drivers is phased out and Linus clearly requested that code which changes behaviour depending on context should either be separated or the context be conveyed in an argument passed by the caller, which usually knows the context.

The semaphore is used as a counting semaphore, initialized with the number of slots in the request pool minus IRQ_REQ_POOL_SIZE - which are reserved for the in_interrupt() user to ensure that a request is always available. The preemptible user will block on the semphore waiting for a request to become available in case there are no requests available.

Replace in_interrupt() with a `can_sleep' argument to indicate if it is safe to block on the sempahore.

Cc: linux-omap@vger.kernel.org Signed-off-by: Ahmed S. Darwish a.darwish@linutronix.de Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- drivers/video/fbdev/omap/hwa742.c | 42 ++++++++++++++++++++----------- 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/drivers/video/fbdev/omap/hwa742.c b/drivers/video/fbdev/omap/hwa742.c index cfe63932f8255..b191bef22d984 100644 --- a/drivers/video/fbdev/omap/hwa742.c +++ b/drivers/video/fbdev/omap/hwa742.c @@ -100,6 +100,14 @@ struct { struct hwa742_request req_pool[REQ_POOL_SIZE]; struct list_head pending_req_list; struct list_head free_req_list; + + /* + * @req_lock: protect request slots pool and its tracking lists + * @req_sema: counter; slot allocators from task contexts must + * push it down before acquiring a slot. This + * guarantees that atomic contexts will always have + * a minimum of IRQ_REQ_POOL_SIZE slots available. + */ struct semaphore req_sema; spinlock_t req_lock;

@@ -224,13 +232,13 @@ static void disable_tearsync(void) hwa742_write_reg(HWA742_NDP_CTRL, b); }

-static inline struct hwa742_request *alloc_req(void) +static inline struct hwa742_request *alloc_req(bool can_sleep) { unsigned long flags; struct hwa742_request *req; int req_flags = 0;

- if (!in_interrupt()) + if (can_sleep) down(&hwa742.req_sema); else req_flags = REQ_FROM_IRQ_POOL; @@ -399,8 +407,8 @@ static void send_frame_complete(void *data) hwa742.int_ctrl->enable_plane(OMAPFB_PLANE_GFX, 0); }

-#define ADD_PREQ(_x, _y, _w, _h) do { \ - req = alloc_req(); \ +#define ADD_PREQ(_x, _y, _w, _h, can_sleep) do {\ + req = alloc_req(can_sleep); \ req->handler = send_frame_handler; \ req->complete = send_frame_complete; \ req->par.update.x = _x; \ @@ -413,7 +421,8 @@ static void send_frame_complete(void *data) } while(0)

static void create_req_list(struct omapfb_update_window *win, - struct list_head *req_head) + struct list_head *req_head, + bool can_sleep) { struct hwa742_request *req; int x = win->x; @@ -427,7 +436,7 @@ static void create_req_list(struct omapfb_update_window *win, color_mode = win->format & OMAPFB_FORMAT_MASK;

if (x & 1) { - ADD_PREQ(x, y, 1, height); + ADD_PREQ(x, y, 1, height, can_sleep); width--; x++; flags &= ~OMAPFB_FORMAT_FLAG_TEARSYNC; @@ -439,19 +448,19 @@ static void create_req_list(struct omapfb_update_window *win,

if (xspan * height * 2 > hwa742.max_transmit_size) { yspan = hwa742.max_transmit_size / (xspan * 2); - ADD_PREQ(x, ystart, xspan, yspan); + ADD_PREQ(x, ystart, xspan, yspan, can_sleep); ystart += yspan; yspan = height - yspan; flags &= ~OMAPFB_FORMAT_FLAG_TEARSYNC; }

- ADD_PREQ(x, ystart, xspan, yspan); + ADD_PREQ(x, ystart, xspan, yspan, can_sleep); x += xspan; width -= xspan; flags &= ~OMAPFB_FORMAT_FLAG_TEARSYNC; } if (width) - ADD_PREQ(x, y, 1, height); + ADD_PREQ(x, y, 1, height, can_sleep); }

static void auto_update_complete(void *data) @@ -461,12 +470,12 @@ static void auto_update_complete(void *data) jiffies + HWA742_AUTO_UPDATE_TIME); }

-static void hwa742_update_window_auto(struct timer_list *unused) +static void __hwa742_update_window_auto(bool can_sleep) { LIST_HEAD(req_list); struct hwa742_request *last;

- create_req_list(&hwa742.auto_update_window, &req_list); + create_req_list(&hwa742.auto_update_window, &req_list, can_sleep); last = list_entry(req_list.prev, struct hwa742_request, entry);

last->complete = auto_update_complete; @@ -475,6 +484,11 @@ static void hwa742_update_window_auto(struct timer_list *unused) submit_req_list(&req_list); }

+static void hwa742_update_window_auto(struct timer_list *unused) +{ + __hwa742_update_window_auto(false); +} + int hwa742_update_window_async(struct fb_info *fbi, struct omapfb_update_window *win, void (*complete_callback)(void *arg), @@ -497,7 +511,7 @@ int hwa742_update_window_async(struct fb_info *fbi, goto out; }

- create_req_list(win, &req_list); + create_req_list(win, &req_list, true); last = list_entry(req_list.prev, struct hwa742_request, entry);

last->complete = complete_callback; @@ -544,7 +558,7 @@ static void hwa742_sync(void) struct hwa742_request *req; struct completion comp;

- req = alloc_req(); + req = alloc_req(true);

req->handler = sync_handler; req->complete = NULL; @@ -599,7 +613,7 @@ static int hwa742_set_update_mode(enum omapfb_update_mode mode) omapfb_notify_clients(hwa742.fbdev, OMAPFB_EVENT_READY); break; case OMAPFB_AUTO_UPDATE: - hwa742_update_window_auto(0); + __hwa742_update_window_auto(true); break; case OMAPFB_UPDATE_DISABLED: break;

The driver uses in_atomic() to distinguish between mdelay() and msleep().

The usage of in_interrupt() in drivers is phased out and Linus clearly requested that code which changes behaviour depending on context should either be separated or the context be conveyed in an argument passed by the caller, which usually knows the context.

I traced the usage of in_interrupt() back to its initial merge: bfe694f833643 ("[ARM] Add ARM AMBA CLCD framebuffer driver.") https://git.kernel.org/history/history/c/bfe694f833643

The driver has been removed and added back in the meantime. I've been looking for the IRQ context as described in the comment and couldn't find it. The functions calling clcdfb_sleep() also call conditionally backlight_update_status() which acquires a mutex. If it is okay to acquire a mutex then it is okay to use msleep() since both functions must be used in preemptible context.

Replace clcdfb_sleep() with msleep().

Cc: Peter Collingbourne pcc@google.com Cc: Russell King linux@armlinux.org.uk Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- drivers/video/fbdev/amba-clcd.c | 17 ++--------------- 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/drivers/video/fbdev/amba-clcd.c b/drivers/video/fbdev/amba-clcd.c index 33595cc4778e9..9ec969e136bfd 100644 --- a/drivers/video/fbdev/amba-clcd.c +++ b/drivers/video/fbdev/amba-clcd.c @@ -35,19 +35,6 @@ /* This is limited to 16 characters when displayed by X startup */ static const char *clcd_name = "CLCD FB";

-/* - * Unfortunately, the enable/disable functions may be called either from - * process or IRQ context, and we _need_ to delay. This is _not_ good. - */ -static inline void clcdfb_sleep(unsigned int ms) -{ - if (in_atomic()) { - mdelay(ms); - } else { - msleep(ms); - } -} - static inline void clcdfb_set_start(struct clcd_fb *fb) { unsigned long ustart = fb->fb.fix.smem_start; @@ -77,7 +64,7 @@ static void clcdfb_disable(struct clcd_fb *fb) val &= ~CNTL_LCDPWR; writel(val, fb->regs + fb->off_cntl);

- clcdfb_sleep(20); + msleep(20); } if (val & CNTL_LCDEN) { val &= ~CNTL_LCDEN; @@ -109,7 +96,7 @@ static void clcdfb_enable(struct clcd_fb *fb, u32 cntl) cntl |= CNTL_LCDEN; writel(cntl, fb->regs + fb->off_cntl);

- clcdfb_sleep(20); + msleep(20);

/* * and now apply power.