On Tue, Jan 22, 2019 at 03:05:23PM -0600, Pierre-Louis Bossart wrote:
On 1/22/19 1:04 PM, Mark Brown wrote:
On Thu, Jan 10, 2019 at 02:11:32PM -0600, Pierre-Louis Bossart wrote:
Messages can be as big as the mailbox, which is hardware dependent. It could be from a few bytes to a larger e.g. 4k page or more, and indeed we need to keep the lock.
Is this copying into an actual mailbox or into some data structure in memory? It looked like it's copying into a buffer for sending rather than the mailbox.
I realize between your feedback and Daniel's that we have a terminology issue. On the Intel side we don't have a dedicated hardware mailbox unit, it's only doorbell registers and shared memory windows.
Ah, that's what I thought was going on. What I was expecting was a sequence of operations along the lines of:
1. Allocate a buffer for the message. 2. Fill in the message. 3. Mark the message as readable by the DSP.
so you only need locking for steps 1 and 3 (and a similar path on return).