net: ipa: use a separate pointer for adjusted GSI memory

This patch actually fixes a bug, though it doesn't affect the two
platforms supported currently.  The fix implements GSI memory
pointers a bit differently.

For IPA version 4.5 and above, the address space for almost all GSI
registers is adjusted downward by a fixed amount.  This is currently
handled by adjusting the I/O virtual address pointer after it has
been mapped.  The bug is that the pointer is not "de-adjusted" as it
should be when it's unmapped.

This patch fixes that error, but it does so by maintaining one "raw"
pointer for the mapped memory range.  This is assigned when the
memory is mapped and used to unmap the memory.  This pointer is also
used to access the two registers that do *not* sit in the "adjusted"
memory space.

Rather than adjusting *that* pointer, we maintain a separate pointer
that's an adjusted copy of the "raw" pointer, and that is used for
most GSI register accesses.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 8 deletions

diff --git a/drivers/net/ipa/gsi_reg.h b/drivers/net/ipa/gsi_reg.h
index 299456e70f28..1622d8cf8dea 100644
--- a/drivers/net/ipa/gsi_reg.h
+++ b/drivers/net/ipa/gsi_reg.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 
 /* Copyright (c) 2015-2018, The Linux Foundation. All rights reserved.
- * Copyright (C) 2018-2020 Linaro Ltd.
+ * Copyright (C) 2018-2021 Linaro Ltd.
  */
 #ifndef _GSI_REG_H_
 #define _GSI_REG_H_
@@ -38,17 +38,21 @@
  * (though the actual limit is hardware-dependent).
  */
 
-/* GSI EE registers as a group are shifted downward by a fixed
- * constant amount for IPA versions 4.5 and beyond.  This applies
- * to all GSI registers we use *except* the ones that disable
- * inter-EE interrupts for channels and event channels.
+/* GSI EE registers as a group are shifted downward by a fixed constant amount
+ * for IPA versions 4.5 and beyond.  This applies to all GSI registers we use
+ * *except* the ones that disable inter-EE interrupts for channels and event
+ * channels.
  *
- * We handle this by adjusting the pointer to the mapped GSI memory
- * region downward.  Then in the one place we use them (gsi_irq_setup())
- * we undo that adjustment for the inter-EE interrupt registers.
+ * The "raw" (not adjusted) GSI register range is mapped, and a pointer to
+ * the mapped range is held in gsi->virt_raw.  The inter-EE interrupt
+ * registers are accessed using that pointer.
+ *
+ * Most registers are accessed using gsi->virt, which is a copy of the "raw"
+ * pointer, adjusted downward by the fixed amount.
  */
 #define GSI_EE_REG_ADJUST			0x0000d000	/* IPA v4.5+ */
 
+/* The two inter-EE IRQ register offsets are relative to gsi->virt_raw */
 #define GSI_INTER_EE_SRC_CH_IRQ_OFFSET \
 			GSI_INTER_EE_N_SRC_CH_IRQ_OFFSET(GSI_EE_AP)
 #define GSI_INTER_EE_N_SRC_CH_IRQ_OFFSET(ee) \
@@ -59,6 +63,7 @@
 #define GSI_INTER_EE_N_SRC_EV_CH_IRQ_OFFSET(ee) \
 			(0x0000c01c + 0x1000 * (ee))
 
+/* All other register offsets are relative to gsi->virt */
 #define GSI_CH_C_CNTXT_0_OFFSET(ch) \
 		GSI_EE_N_CH_C_CNTXT_0_OFFSET((ch), GSI_EE_AP)
 #define GSI_EE_N_CH_C_CNTXT_0_OFFSET(ch, ee) \