[PATCH v8 5/7] cache: Add L2 cache management for Andes AX45MP RISC-V core

From: Prabhakar
Date: Wed Apr 12 2023 - 07:09:55 EST

From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>

I/O Coherence Port (IOCP) provides an AXI interface for connecting
external non-caching masters, such as DMA controllers. The accesses
from IOCP are coherent with D-Caches and L2 Cache.

IOCP is a specification option and is disabled on the Renesas RZ/Five
SoC due to this reason IP blocks using DMA will fail.

The 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.
Below are the memory attributes supported:
* Device, Non-bufferable
* Device, bufferable
* Memory, Non-cacheable, Non-bufferable
* Memory, Non-cacheable, Bufferable
* Memory, Write-back, No-allocate
* Memory, Write-back, Read-allocate
* Memory, Write-back, Write-allocate
* Memory, Write-back, Read and Write-allocate

More info about PMA (section 10.3):
Link: http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf

As a workaround for SoCs with IOCP disabled CMO needs to be handled by
software. Firstly OpenSBI configures the memory region as
"Memory, Non-cacheable, Bufferable" and passes this region as a global
shared dma pool as a DT node. With DMA_GLOBAL_POOL enabled all DMA
allocations happen from this region and synchronization callbacks are
implemented to synchronize when doing DMA transactions.

Example PMA region passes as a DT node from OpenSBI:
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;
};
};

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
---
v7 -> v8
* Dropped function pointer usage
* Now exporting the functions for clean/inval/flush
* Switched to using early_initcall instead of arch_initcall
* Dropped entry for "include/cache" from MAINTAINERS
* Dropped dependency of RISCV on AX45MP_L2_CACHE
* Returning error in case of cache line mismatch
* Renamed clean/inval/flush functions

v6 -> v7
* Implemented flush callback
* Dropped using riscv_dma_noncoherent_cmo_ops

v5 -> v6
* Moved driver to cache folder
* Switched to new API for CMO

v4 -> v5
* Dropped code for configuring L2 cache
* Dropped code for configuring PMA
* Updated commit message
* Added comments
* Changed static branch enable/disable order

RFC v3 -> v4
* Made use of runtime patching instead of compile time
* Now just exposing single function ax45mp_no_iocp_cmo() for CMO handling
* Added a check to make sure cache line size is always 64 bytes
* Renamed folder rzf -> rzfive
* Improved Kconfig description
* Dropped L2 cache configuration
* Dropped unnecessary casts
* Fixed comments pointed by Geert.
---
MAINTAINERS | 7 ++
drivers/Kconfig | 2 +
drivers/Makefile | 1 +
drivers/cache/Kconfig | 10 ++
drivers/cache/Makefile | 3 +
drivers/cache/ax45mp_cache.c | 222 +++++++++++++++++++++++++++++++++++
6 files changed, 245 insertions(+)
create mode 100644 drivers/cache/Kconfig
create mode 100644 drivers/cache/Makefile
create mode 100644 drivers/cache/ax45mp_cache.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 3afd45f71043..9afd39a23524 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -19898,6 +19898,13 @@ S: Supported
T: git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
F: drivers/staging/

+STANDALONE CACHE CONTROLLER DRIVERS
+M: Conor Dooley <conor@xxxxxxxxxx>
+L: linux-riscv@xxxxxxxxxxxxxxxxxxx
+S: Maintained
+T: git https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git/
+F: drivers/cache
+
STARFIRE/DURALAN NETWORK DRIVER
M: Ion Badulescu <ionut@xxxxxxxxxx>
S: Odd Fixes
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 968bd0a6fd78..44abd2cba3a3 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -15,6 +15,8 @@ source "drivers/base/Kconfig"

source "drivers/bus/Kconfig"

+source "drivers/cache/Kconfig"
+
source "drivers/connector/Kconfig"

source "drivers/firmware/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index 20b118dca999..db5a8115093f 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -11,6 +11,7 @@ ifdef building_out_of_srctree
MAKEFLAGS += --include-dir=$(srctree)
endif

+obj-y += cache/
obj-y += irqchip/
obj-y += bus/

diff --git a/drivers/cache/Kconfig b/drivers/cache/Kconfig
new file mode 100644
index 000000000000..b97269cbd149
--- /dev/null
+++ b/drivers/cache/Kconfig
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0
+menu "Cache Drivers"
+
+config AX45MP_L2_CACHE
+ bool "Andes Technology AX45MP L2 Cache controller"
+ depends on RISCV_DMA_NONCOHERENT
+ help
+ Support for the L2 cache controller on Andes Technology AX45MP platforms.
+
+endmenu
diff --git a/drivers/cache/Makefile b/drivers/cache/Makefile
new file mode 100644
index 000000000000..2012e7fb978d
--- /dev/null
+++ b/drivers/cache/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+obj-$(CONFIG_AX45MP_L2_CACHE) += ax45mp_cache.o
diff --git a/drivers/cache/ax45mp_cache.c b/drivers/cache/ax45mp_cache.c
new file mode 100644
index 000000000000..cfc40b967c55
--- /dev/null
+++ b/drivers/cache/ax45mp_cache.c
@@ -0,0 +1,222 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * non-coherent cache functions for Andes AX45MP
+ *
+ * Copyright (C) 2023 Renesas Electronics Corp.
+ */
+
+#include <linux/cacheflush.h>
+#include <linux/cacheinfo.h>
+#include <linux/dma-direction.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+
+/* L2 cache registers */
+#define AX45MP_L2C_REG_CTL_OFFSET 0x8
+
+#define AX45MP_L2C_REG_C0_CMD_OFFSET 0x40
+#define AX45MP_L2C_REG_C0_ACC_OFFSET 0x48
+#define AX45MP_L2C_REG_STATUS_OFFSET 0x80
+
+/* D-cache operation */
+#define AX45MP_CCTL_L1D_VA_INVAL 0 /* Invalidate an L1 cache entry */
+#define AX45MP_CCTL_L1D_VA_WB 1 /* Write-back an L1 cache entry */
+
+/* L2 CCTL status */
+#define AX45MP_CCTL_L2_STATUS_IDLE 0
+
+/* L2 CCTL status cores mask */
+#define AX45MP_CCTL_L2_STATUS_C0_MASK 0xf
+
+/* L2 cache operation */
+#define AX45MP_CCTL_L2_PA_INVAL 0x8 /* Invalidate an L2 cache entry */
+#define AX45MP_CCTL_L2_PA_WB 0x9 /* Write-back an L2 cache entry */
+
+#define AX45MP_L2C_REG_PER_CORE_OFFSET 0x10
+#define AX45MP_CCTL_L2_STATUS_PER_CORE_OFFSET 4
+
+#define AX45MP_L2C_REG_CN_CMD_OFFSET(n) \
+ (AX45MP_L2C_REG_C0_CMD_OFFSET + ((n) * AX45MP_L2C_REG_PER_CORE_OFFSET))
+#define AX45MP_L2C_REG_CN_ACC_OFFSET(n) \
+ (AX45MP_L2C_REG_C0_ACC_OFFSET + ((n) * AX45MP_L2C_REG_PER_CORE_OFFSET))
+#define AX45MP_CCTL_L2_STATUS_CN_MASK(n) \
+ (AX45MP_CCTL_L2_STATUS_C0_MASK << ((n) * AX45MP_CCTL_L2_STATUS_PER_CORE_OFFSET))
+
+#define AX45MP_CCTL_REG_UCCTLBEGINADDR_NUM 0x80b
+#define AX45MP_CCTL_REG_UCCTLCOMMAND_NUM 0x80c
+
+#define AX45MP_CACHE_LINE_SIZE 64
+
+struct ax45mp_priv {
+ void __iomem *l2c_base;
+ u32 ax45mp_cache_line_size;
+};
+
+static struct ax45mp_priv ax45mp_priv;
+
+/* L2 Cache operations */
+static inline uint32_t ax45mp_cpu_l2c_get_cctl_status(void)
+{
+ return readl(ax45mp_priv.l2c_base + AX45MP_L2C_REG_STATUS_OFFSET);
+}
+
+static void ax45mp_cpu_cache_operation(unsigned long start, unsigned long end,
+ unsigned long line_size, unsigned int l1_op,
+ unsigned int l2_op)
+{
+ void __iomem *base = ax45mp_priv.l2c_base;
+ int mhartid = smp_processor_id();
+ unsigned long pa;
+
+ while (end > start) {
+ csr_write(AX45MP_CCTL_REG_UCCTLBEGINADDR_NUM, start);
+ csr_write(AX45MP_CCTL_REG_UCCTLCOMMAND_NUM, l1_op);
+
+ pa = virt_to_phys((void *)start);
+ writel(pa, base + AX45MP_L2C_REG_CN_ACC_OFFSET(mhartid));
+ writel(l2_op, base + AX45MP_L2C_REG_CN_CMD_OFFSET(mhartid));
+ while ((ax45mp_cpu_l2c_get_cctl_status() &
+ AX45MP_CCTL_L2_STATUS_CN_MASK(mhartid)) !=
+ AX45MP_CCTL_L2_STATUS_IDLE)
+ ;
+
+ start += line_size;
+ }
+}
+
+/* Write-back L1 and L2 cache entry */
+static inline void ax45mp_cpu_dcache_wb_range(unsigned long start, unsigned long end,
+ unsigned long line_size)
+{
+ ax45mp_cpu_cache_operation(start, end, line_size,
+ AX45MP_CCTL_L1D_VA_WB,
+ AX45MP_CCTL_L2_PA_WB);
+}
+
+/* Invalidate the L1 and L2 cache entry */
+static inline void ax45mp_cpu_dcache_inval_range(unsigned long start, unsigned long end,
+ unsigned long line_size)
+{
+ ax45mp_cpu_cache_operation(start, end, line_size,
+ AX45MP_CCTL_L1D_VA_INVAL,
+ AX45MP_CCTL_L2_PA_INVAL);
+}
+
+void ax45mp_dma_cache_inv(void *vaddr, unsigned long size)
+{
+ unsigned long start = (unsigned long)vaddr;
+ char cache_buf[2][AX45MP_CACHE_LINE_SIZE];
+ unsigned long end = start + size;
+ unsigned long old_start = start;
+ unsigned long old_end = end;
+ unsigned long line_size;
+ unsigned long flags;
+
+ if (unlikely(start == end))
+ return;
+
+ line_size = ax45mp_priv.ax45mp_cache_line_size;
+
+ memset(&cache_buf, 0x0, sizeof(cache_buf));
+ start = start & (~(line_size - 1));
+ end = ((end + line_size - 1) & (~(line_size - 1)));
+
+ local_irq_save(flags);
+ if (unlikely(start != old_start))
+ memcpy(&cache_buf[0][0], (void *)start, line_size);
+
+ if (unlikely(end != old_end))
+ memcpy(&cache_buf[1][0], (void *)(old_end & (~(line_size - 1))), line_size);
+
+ ax45mp_cpu_dcache_inval_range(start, end, line_size);
+
+ if (unlikely(start != old_start))
+ memcpy((void *)start, &cache_buf[0][0], (old_start & (line_size - 1)));
+
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(ax45mp_dma_cache_inv);
+
+void ax45mp_dma_cache_wback(void *vaddr, unsigned long size)
+{
+ unsigned long start = (unsigned long)vaddr;
+ unsigned long end = start + size;
+ unsigned long line_size;
+ unsigned long flags;
+
+ line_size = ax45mp_priv.ax45mp_cache_line_size;
+ start = start & (~(line_size - 1));
+ local_irq_save(flags);
+ ax45mp_cpu_dcache_wb_range(start, end, line_size);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(ax45mp_dma_cache_wback);
+
+void ax45mp_dma_cache_wback_inv(void *vaddr, unsigned long size)
+{
+ ax45mp_dma_cache_wback(vaddr, size);
+ ax45mp_dma_cache_inv(vaddr, size);
+}
+EXPORT_SYMBOL_GPL(ax45mp_dma_cache_wback_inv);
+
+static int ax45mp_get_l2_line_size(struct device_node *np)
+{
+ int ret;
+
+ ret = of_property_read_u32(np, "cache-line-size", &ax45mp_priv.ax45mp_cache_line_size);
+ if (ret) {
+ pr_err("Failed to get cache-line-size, defaulting to 64 bytes\n");
+ return ret;
+ }
+
+ if (ax45mp_priv.ax45mp_cache_line_size != AX45MP_CACHE_LINE_SIZE) {
+ pr_err("Expected cache-line-size to be 64 bytes (found:%u)\n",
+ ax45mp_priv.ax45mp_cache_line_size);
+ return ret;
+ }
+
+ return 0;
+}
+
+static const struct of_device_id ax45mp_cache_ids[] = {
+ { .compatible = "andestech,ax45mp-cache" },
+ { /* sentinel */ }
+};
+
+static int __init ax45mp_cache_init(void)
+{
+ struct device_node *np;
+ struct resource res;
+ int ret;
+
+ np = of_find_matching_node(NULL, ax45mp_cache_ids);
+ if (!of_device_is_available(np))
+ return -ENODEV;
+
+ ret = of_address_to_resource(np, 0, &res);
+ if (ret)
+ return ret;
+
+ /*
+ * If IOCP is present on the Andes AX45MP core riscv_cbom_block_size
+ * will be 0 for sure, so we can definitely rely on it. If
+ * riscv_cbom_block_size = 0 we don't need to handle CMO using SW any
+ * more so we just return success here and only if its being set we
+ * continue further in the probe path.
+ */
+ if (!riscv_cbom_block_size)
+ return 0;
+
+ ax45mp_priv.l2c_base = ioremap(res.start, resource_size(&res));
+ if (!ax45mp_priv.l2c_base)
+ return -ENOMEM;
+
+ ret = ax45mp_get_l2_line_size(np);
+ if (ret) {
+ iounmap(ax45mp_priv.l2c_base);
+ return ret;
+ }
+
+ return 0;
+}
+early_initcall(ax45mp_cache_init);
--
2.25.1