| Message ID | 20181026134813.7775-10-nsaenzjulienne@suse.de (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
| Series | staging: vchiq: remove dead code & misc fixes | expand |
Hi Nicolas, > Nicolas Saenz Julienne <nsaenzjulienne@suse.de> hat am 26. Oktober 2018 um 15:48 geschrieben: > > > vchiq_init_state() initialises a series of semaphores to then call > remote_event_create() on the same semaphores, which initializes them > again. i would prefer to have all init stuff at one place in vchiq_init_state() and drop this ugliness from remote_event_create() instead. Is this possible?
Hi Stefan, thanks for spending the time reviewing the code. I took note of the rest of comments. On Sun, 2018-10-28 at 21:45 +0100, Stefan Wahren wrote: > Hi Nicolas, > > > Nicolas Saenz Julienne <nsaenzjulienne@suse.de> hat am 26. Oktober > > 2018 um 15:48 geschrieben: > > > > > > vchiq_init_state() initialises a series of semaphores to then call > > remote_event_create() on the same semaphores, which initializes > > them > > again. > > i would prefer to have all init stuff at one place in > vchiq_init_state() and drop this ugliness from remote_event_create() > instead. Is this possible? As I'm sure you're aware of, REMOTE_EVENT_T is shared between the CPU and VC4, which can't be expanded. And since storing a pointer is out of question because of arm64, I can only think of storing an index to an array of completions in the shared structure instead of the pointer magic implemented right now. It would be a little more explicit. Then we could completely decouple both initializations. I'm not sure if it's similar to what you had in mind. On a semi-related topic, I'm curious to know why these shared structures aren't set with the "__packed" preprocessor macro. Any ideas? As fas as I've been told, in general, the compiler may reorder or add unexpected padding to any structure. Which would be very bad in this case. Regards, Nicolas
Am 06.11.18 um 16:41 schrieb Nicolas Saenz Julienne: > Hi Stefan, > thanks for spending the time reviewing the code. I took note of the > rest of comments. > > On Sun, 2018-10-28 at 21:45 +0100, Stefan Wahren wrote: >> Hi Nicolas, >> >>> Nicolas Saenz Julienne <nsaenzjulienne@suse.de> hat am 26. Oktober >>> 2018 um 15:48 geschrieben: >>> >>> >>> vchiq_init_state() initialises a series of semaphores to then call >>> remote_event_create() on the same semaphores, which initializes >>> them >>> again. >> i would prefer to have all init stuff at one place in >> vchiq_init_state() and drop this ugliness from remote_event_create() >> instead. Is this possible? > As I'm sure you're aware of, REMOTE_EVENT_T is shared between the CPU > and VC4, which can't be expanded. And since storing a pointer is out of > question because of arm64, I can only think of storing an index to an > array of completions in the shared structure instead of the pointer > magic implemented right now. It would be a little more explicit. Then > we could completely decouple both initializations. I'm not sure if it's > similar to what you had in mind. I don't think so, this was my intention: static inline void remote_event_create(VCHIQ_STATE_T *state, REMOTE_EVENT_T *event) { event->armed = 0; /* Don't clear the 'fired' flag because it may already have been set ** by the other side. */ - sema_init((struct semaphore *)((char *)state + event->event), 0); } > > On a semi-related topic, I'm curious to know why these shared > structures aren't set with the "__packed" preprocessor macro. Any > ideas? As fas as I've been told, in general, the compiler may reorder > or add unexpected padding to any structure. Which would be very bad in > this case. This would be better, but i assume the firmware side uses the same source code. So using __packed only on ARM side could also break :-( > > Regards, > Nicolas
On Tue, 2018-11-06 at 17:06 +0100, Stefan Wahren wrote: > Am 06.11.18 um 16:41 schrieb Nicolas Saenz Julienne: > > Hi Stefan, > > thanks for spending the time reviewing the code. I took note of the > > rest of comments. > > > > On Sun, 2018-10-28 at 21:45 +0100, Stefan Wahren wrote: > > > Hi Nicolas, > > > > > > > Nicolas Saenz Julienne <nsaenzjulienne@suse.de> hat am 26. > > > > Oktober > > > > 2018 um 15:48 geschrieben: > > > > > > > > > > > > vchiq_init_state() initialises a series of semaphores to then > > > > call > > > > remote_event_create() on the same semaphores, which initializes > > > > them > > > > again. > > > i would prefer to have all init stuff at one place in > > > vchiq_init_state() and drop this ugliness from > > > remote_event_create() > > > instead. Is this possible? > > As I'm sure you're aware of, REMOTE_EVENT_T is shared between the > > CPU > > and VC4, which can't be expanded. And since storing a pointer is > > out of > > question because of arm64, I can only think of storing an index to > > an > > array of completions in the shared structure instead of the pointer > > magic implemented right now. It would be a little more explicit. > > Then > > we could completely decouple both initializations. I'm not sure if > > it's > > similar to what you had in mind. > > I don't think so, this was my intention: > > static inline void > remote_event_create(VCHIQ_STATE_T *state, REMOTE_EVENT_T *event) > { > event->armed = 0; > /* Don't clear the 'fired' flag because it may already have been > set > ** by the other side. */ > - sema_init((struct semaphore *)((char *)state + event->event), > 0); > } Fair enough, even simpler. > > > > On a semi-related topic, I'm curious to know why these shared > > structures aren't set with the "__packed" preprocessor macro. Any > > ideas? As fas as I've been told, in general, the compiler may > > reorder > > or add unexpected padding to any structure. Which would be very bad > > in > > this case. > > This would be better, but i assume the firmware side uses the same > source code. So using __packed only on ARM side could also break :-( True. Yet in that case, aren't we still relying on the fact that both compilers are going to behave the same way? > > > Regards, > > Nicolas
diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c index dee5ea7bfe4f..6242357735b9 100644 --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c @@ -2200,11 +2200,6 @@ vchiq_init_state(VCHIQ_STATE_T *state, VCHIQ_SLOT_ZERO_T *slot_zero) sema_init(&state->connect, 0); mutex_init(&state->mutex); - sema_init(&state->trigger_event, 0); - sema_init(&state->recycle_event, 0); - sema_init(&state->sync_trigger_event, 0); - sema_init(&state->sync_release_event, 0); - mutex_init(&state->slot_mutex); mutex_init(&state->recycle_mutex); mutex_init(&state->sync_mutex);
vchiq_init_state() initialises a series of semaphores to then call remote_event_create() on the same semaphores, which initializes them again. Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> --- .../staging/vc04_services/interface/vchiq_arm/vchiq_core.c | 5 ----- 1 file changed, 5 deletions(-)