Some firmwares expect the OS drivers to configure the CTABLE
entries publishing dynamically allocated memory regions. For
example, the PRU Ethernet firmwares use the C28 and C30 entries
for retrieving the Shared RAM and System SRAM (OCMC) areas
allocated by the PRU Ethernet client driver.

Provide a way for users to do that through a new API,
pru_rproc_set_ctable(). The API returns 0 on success and
a negative value on error.

NOTE:
The programmable CTABLE entries are typically re-programmed by
the PRU firmwares when dealing with a certain block of memory
during block processing. This API provides an interface to the
PRU client drivers to publish a dynamically allocated memory
block with the PRU firmware using a CTABLE entry instead of a
negotiated address in shared memory. Additional synchronization
may be needed between the PRU client drivers and firmwares if
different addresses needs to be published at run-time reusing
the same CTABLE entry.

CTABLE for stands for "constant table".
Each CTable entry just holds the upper address bits so PRU can
reference to external memory with larger address bits.

For use case please see
prueth_sw_emac_config() in "drivers/net/ethernet/ti/prueth_switch.c"

            /* Set in constant table C28 of PRUn to ICSS Shared memory */
             pru_rproc_set_ctable(prueth->pru0, PRU_C28, sharedramaddr);
             pru_rproc_set_ctable(prueth->pru1, PRU_C28, sharedramaddr);

            /* Set in constant table C30 of PRUn to OCMC memory */
             pru_rproc_set_ctable(prueth->pru0, PRU_C30, ocmcaddr);
             pru_rproc_set_ctable(prueth->pru1, PRU_C30, ocmcaddr);
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: MD Danish Anwar <danishanwar@ti.com>
Link: https://lore.kernel.org/r/20230106121046.886863-6-danishanwar@ti.comSigned-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>