[PATCH] remoteproc: pru: Fix loading of GNU Binutils ELF

[Dimitar Dimitrov <dimitar@dinux.eu>]

PRU port of GNU Binutils lacks support for separate address spaces.
PRU IRAM addresses are marked with artificial offset to differentiate
them from DRAM addresses. Hence remoteproc must mask IRAM addresses
coming from GNU ELF in order to get the true hardware address.

Patch was tested on top of latest linux-remoteproc/for-next branch:
  commit 4c0943255805 ("Merge branches 'hwspinlock-next', 'rpmsg-next' and 'rproc-next' into for-next")'

PRU firmware used for testing was the example in:
  https://github.com/dinuxbg/pru-gcc-examples/tree/master/blinking-led/pru

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>
---
 drivers/remoteproc/pru_rproc.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/remoteproc/pru_rproc.c b/drivers/remoteproc/pru_rproc.c
index 2667919d76b3..b03114bbb9ab 100644
--- a/drivers/remoteproc/pru_rproc.c
+++ b/drivers/remoteproc/pru_rproc.c
@@ -61,6 +61,18 @@
 #define PRU_SDRAM_DA	0x2000	/* Secondary Data RAM */
 #define PRU_SHRDRAM_DA	0x10000 /* Shared Data RAM */
 
+/*
+ * GNU binutils do not support multiple address spaces. The GNU linker's
+ * default linker script places IRAM at an arbitrary high offset, in order
+ * to differentiate it from DRAM. Hence we need to strip the artificial offset
+ * in the IRAM addresses coming from the ELF file.
+ *
+ * The TI proprietary linker would never set those higher IRAM address bits
+ * anyway. PRU architecture limits the program counter to 16 bit word
+ * addresses.
+ */
+#define PRU_IRAM_DA_MASK	0xfffff
+
 #define MAX_PRU_SYS_EVENTS 160
 
 /**
@@ -450,6 +462,8 @@ static void *pru_i_da_to_va(struct pru_rproc *pru, u32 da, size_t len)
 	if (len == 0)
 		return NULL;
 
+	da &= PRU_IRAM_DA_MASK;
+
 	if (da >= PRU_IRAM_DA &&
 	    da + len <= PRU_IRAM_DA + pru->mem_regions[PRU_IOMEM_IRAM].size) {
 		offset = da - PRU_IRAM_DA;
-- 
2.20.1