Merge patch series "Add non-coherent DMA support for AX45MP"

Prabhakar <prabhakar.csengg@gmail.com> says:

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>

non-coherent DMA support for AX45MP
====================================

On the Andes AX45MP core, cache coherency is a specification option so it
may not be supported. In this case DMA will fail. To get around with this
issue this patch series does the below:

1] Andes alternative ports is implemented as errata which checks if the
IOCP is missing and only then applies to CMO errata. One vendor specific
SBI EXT (ANDES_SBI_EXT_IOCP_SW_WORKAROUND) is implemented as part of
errata.

Below are the configs which Andes port provides (and are selected by
RZ/Five):
      - ERRATA_ANDES
      - ERRATA_ANDES_CMO

OpenSBI patch supporting ANDES_SBI_EXT_IOCP_SW_WORKAROUND SBI is now
part v1.3 release.

2] Andes AX45MP core has a Programmable Physical Memory Attributes (PMA)
block that allows dynamic adjustment of memory attributes in the runtime.
It contains a configurable amount of PMA entries implemented as CSR
registers to control the attributes of memory locations in interest.
OpenSBI configures the PMA regions as required and creates a reserve memory
node and propagates it to the higher boot stack.

Currently OpenSBI (upstream) configures the required PMA region and passes
this a shared DMA pool to Linux.

    reserved-memory {
        #address-cells = <2>;
        #size-cells = <2>;
        ranges;

        pma_resv0@58000000 {
            compatible = "shared-dma-pool";
            reg = <0x0 0x58000000 0x0 0x08000000>;
            no-map;
            linux,dma-default;
        };
    };

The above shared DMA pool gets appended to Linux DTB so the DMA memory
requests go through this region.

3] We provide callbacks to synchronize specific content between memory and
cache.

4] RZ/Five SoC selects the below configs
        - AX45MP_L2_CACHE
        - DMA_GLOBAL_POOL
        - ERRATA_ANDES
        - ERRATA_ANDES_CMO

----------x---------------------x--------------------x---------------x----

* b4-shazam-merge:
  soc: renesas: Kconfig: Select the required configs for RZ/Five SoC
  cache: Add L2 cache management for Andes AX45MP RISC-V core
  dt-bindings: cache: andestech,ax45mp-cache: Add DT binding documentation for L2 cache controller
  riscv: mm: dma-noncoherent: nonstandard cache operations support
  riscv: errata: Add Andes alternative ports
  riscv: asm: vendorid_list: Add Andes Technology to the vendors list

Link: https://lore.kernel.org/r/20230818135723.80612-1-prabhakar.mahadev-lad.rj@bp.renesas.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

3 files changed, 68 insertions, 0 deletions

diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index 7b2637c8c332..8a2739485123 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -2,5 +2,6 @@ ifdef CONFIG_RELOCATABLE
 KBUILD_CFLAGS += -fno-pie
 endif
 
+obj-$(CONFIG_ERRATA_ANDES) += andes/
 obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
 obj-$(CONFIG_ERRATA_THEAD) += thead/
diff --git a/arch/riscv/errata/andes/Makefile b/arch/riscv/errata/andes/Makefile
new file mode 100644
index 000000000000..2d644e19caef
--- /dev/null
+++ b/arch/riscv/errata/andes/Makefile
@@ -0,0 +1 @@
+obj-y += errata.o
diff --git a/arch/riscv/errata/andes/errata.c b/arch/riscv/errata/andes/errata.c
new file mode 100644
index 000000000000..197db68cc8da
--- /dev/null
+++ b/arch/riscv/errata/andes/errata.c
@@ -0,0 +1,66 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Erratas to be applied for Andes CPU cores
+ *
+ *  Copyright (C) 2023 Renesas Electronics Corporation.
+ *
+ * Author: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
+ */
+
+#include <linux/memory.h>
+#include <linux/module.h>
+
+#include <asm/alternative.h>
+#include <asm/cacheflush.h>
+#include <asm/errata_list.h>
+#include <asm/patch.h>
+#include <asm/processor.h>
+#include <asm/sbi.h>
+#include <asm/vendorid_list.h>
+
+#define ANDESTECH_AX45MP_MARCHID	0x8000000000008a45UL
+#define ANDESTECH_AX45MP_MIMPID		0x500UL
+#define ANDESTECH_SBI_EXT_ANDES		0x0900031E
+
+#define ANDES_SBI_EXT_IOCP_SW_WORKAROUND	1
+
+static long ax45mp_iocp_sw_workaround(void)
+{
+	struct sbiret ret;
+
+	/*
+	 * ANDES_SBI_EXT_IOCP_SW_WORKAROUND SBI EXT checks if the IOCP is missing and
+	 * cache is controllable only then CMO will be applied to the platform.
+	 */
+	ret = sbi_ecall(ANDESTECH_SBI_EXT_ANDES, ANDES_SBI_EXT_IOCP_SW_WORKAROUND,
+			0, 0, 0, 0, 0, 0);
+
+	return ret.error ? 0 : ret.value;
+}
+
+static bool errata_probe_iocp(unsigned int stage, unsigned long arch_id, unsigned long impid)
+{
+	if (!IS_ENABLED(CONFIG_ERRATA_ANDES_CMO))
+		return false;
+
+	if (arch_id != ANDESTECH_AX45MP_MARCHID || impid != ANDESTECH_AX45MP_MIMPID)
+		return false;
+
+	if (!ax45mp_iocp_sw_workaround())
+		return false;
+
+	/* Set this just to make core cbo code happy */
+	riscv_cbom_block_size = 1;
+	riscv_noncoherent_supported();
+
+	return true;
+}
+
+void __init_or_module andes_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+					      unsigned long archid, unsigned long impid,
+					      unsigned int stage)
+{
+	errata_probe_iocp(stage, archid, impid);
+
+	/* we have nothing to patch here ATM so just return back */
+}