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The command queue carries commands from > the driver to GSP-RM, and the message queue carries messages from GSP-RM > to the driver. Each ring buffer has a write pointer and a read pointer. > > Msgq v0, which the r570 firmware uses, keeps both pointers of each ring > buffer in that ring buffer's header, in shared memory. Msgq v2, which > the r000 firmware uses, keeps the four pointers, two per ring buffer, in > four BAR0 registers instead: > > NV_PGSP_QUEUE_HEAD command queue write pointer > NV_PGSP_QUEUE_TAIL command queue read pointer > NV_PGSP_MSGQ_HEAD message queue write pointer > NV_PGSP_MSGQ_TAIL message queue read pointer > > The GSP numbers its queues 0 through 7, and each numbered queue is one > such pair of ring buffers with its own four pointer registers, so the > hardware has 32 pointer registers in all. Nova-core uses queue 0 only. > > A write to NV_PGSP_QUEUE_HEAD also interrupts the GSP. Msgq v0 uses that > write as the doorbell, so nova-core already declares NV_PGSP_QUEUE_HEAD. > > Declare the other three, NV_PGSP_QUEUE_TAIL, NV_PGSP_MSGQ_HEAD and > NV_PGSP_MSGQ_TAIL, each as a scalar at its queue 0 offset rather than as > an array of eight. I understand that at the moment we are only using the first of these registers (and `NV_PGSP_QUEUE_HEAD` was already declared that way), but technically they are arrays of 8 - let's take the opportunity to declare them accurately and stop deriving from the hardware definition.