Re: [PATCH v4 7/7] soc: renesas: Add L2 cache management for RZ/Five SoC

From: Lad, Prabhakar
Date: Thu Nov 24 2022 - 14:57:14 EST

Hi Heiko,

Thank you for the review.

On Thu, Nov 24, 2022 at 6:30 PM Heiko Stübner <heiko@xxxxxxxxx> wrote:
>
> Am Donnerstag, 24. November 2022, 18:22:07 CET schrieb Prabhakar:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > On the AX45MP core, cache coherency is a specification option so it may
> > not be supported. In this case DMA will fail. As a workaround, firstly we
> > allocate a global dma coherent pool from which DMA allocations are taken
> > and marked as non-cacheable + bufferable using the PMA region as specified
> > in the device tree. Synchronization callbacks are implemented to
> > synchronize when doing DMA transactions.
> >
> > 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
> >
> > This patch adds support to configure the memory attributes of the memory
> > regions as passed from the l2 cache node and exposes the cache management
> > ops.
> >
> > More info about PMA (section 10.3):
> > Link: http://www.andestech.com/wp-content/uploads/AX45MP-1C-Rev.-5.0.0-Datasheet.pdf
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > ---
> > 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, apart from use of PTR_ALIGN_XYZ() macros.
> > ---
> > arch/riscv/include/asm/cacheflush.h | 8 +
> > arch/riscv/include/asm/errata_list.h | 32 +-
> > drivers/soc/renesas/Kconfig | 7 +
> > drivers/soc/renesas/Makefile | 2 +
> > drivers/soc/renesas/rzfive/Kconfig | 6 +
> > drivers/soc/renesas/rzfive/Makefile | 3 +
> > drivers/soc/renesas/rzfive/ax45mp_cache.c | 415 ++++++++++++++++++++++
> > drivers/soc/renesas/rzfive/ax45mp_sbi.h | 29 ++
> > 8 files changed, 496 insertions(+), 6 deletions(-)
> > create mode 100644 drivers/soc/renesas/rzfive/Kconfig
> > create mode 100644 drivers/soc/renesas/rzfive/Makefile
> > create mode 100644 drivers/soc/renesas/rzfive/ax45mp_cache.c
> > create mode 100644 drivers/soc/renesas/rzfive/ax45mp_sbi.h
> >
> > diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
> > index 4a04d1be7c67..3226f3aceafe 100644
> > --- a/arch/riscv/include/asm/cacheflush.h
> > +++ b/arch/riscv/include/asm/cacheflush.h
> > @@ -61,6 +61,14 @@ static inline void riscv_noncoherent_supported(void) {}
> > #define SYS_RISCV_FLUSH_ICACHE_LOCAL 1UL
> > #define SYS_RISCV_FLUSH_ICACHE_ALL (SYS_RISCV_FLUSH_ICACHE_LOCAL)
> >
> > +#ifdef CONFIG_AX45MP_L2_CACHE
> > +extern asmlinkage void ax45mp_no_iocp_cmo(unsigned int cache_size, void *vaddr,
> > + size_t size, int dir, int ops);
> > +#else
> > +inline void ax45mp_no_iocp_cmo(unsigned int cache_size, void *vaddr,
> > + size_t size, int dir, int ops) {}
> > +#endif
> > +
> > #include <asm-generic/cacheflush.h>
> >
> > #endif /* _ASM_RISCV_CACHEFLUSH_H */
> > diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> > index 48e899a8e7a9..300fed3bfd80 100644
> > --- a/arch/riscv/include/asm/errata_list.h
> > +++ b/arch/riscv/include/asm/errata_list.h
> > @@ -125,8 +125,8 @@ asm volatile(ALTERNATIVE( \
> > #define THEAD_SYNC_S ".long 0x0190000b"
> >
> > #define ALT_CMO_OP(_op, _start, _size, _cachesize, _dir, _ops) \
> > -asm volatile(ALTERNATIVE_2( \
> > - __nops(6), \
> > +asm volatile(ALTERNATIVE_3( \
> > + __nops(14), \
> > "mv a0, %1\n\t" \
> > "j 2f\n\t" \
> > "3:\n\t" \
> > @@ -134,7 +134,7 @@ asm volatile(ALTERNATIVE_2( \
> > "add a0, a0, %0\n\t" \
> > "2:\n\t" \
> > "bltu a0, %2, 3b\n\t" \
> > - "nop", 0, CPUFEATURE_ZICBOM, CONFIG_RISCV_ISA_ZICBOM, \
> > + __nops(8), 0, CPUFEATURE_ZICBOM, CONFIG_RISCV_ISA_ZICBOM, \
> > "mv a0, %1\n\t" \
> > "j 2f\n\t" \
> > "3:\n\t" \
> > @@ -142,8 +142,28 @@ asm volatile(ALTERNATIVE_2( \
> > "add a0, a0, %0\n\t" \
> > "2:\n\t" \
> > "bltu a0, %2, 3b\n\t" \
> > - THEAD_SYNC_S, THEAD_VENDOR_ID, \
> > - ERRATA_THEAD_CMO, CONFIG_ERRATA_THEAD_CMO) \
> > + THEAD_SYNC_S "\n\t" \
> > + __nops(8), THEAD_VENDOR_ID, \
> > + ERRATA_THEAD_CMO, CONFIG_ERRATA_THEAD_CMO, \
> > + ".option push\n\t\n\t" \
> > + ".option norvc\n\t" \
> > + ".option norelax\n\t"> \
>
> alternatives already do the norvc + norelax options anyway for old and new instructions,
> so the .option stuff shouldn't be necessary I guess?
>
I did a quick run with .option stuff and all seems to be OK. I'll do
some rigorous testing and get rid of it in the next version.
>
> > + "addi sp,sp,-16\n\t" \
> > + "sd s0,0(sp)\n\t" \
> > + "sd ra,8(sp)\n\t" \
> > + "addi s0,sp,16\n\t" \
> > + "mv a4,%6\n\t" \
> > + "mv a3,%5\n\t" \
> > + "mv a2,%4\n\t" \
> > + "mv a1,%3\n\t" \
> > + "mv a0,%0\n\t" \
> > + "call ax45mp_no_iocp_cmo\n\t" \
> > + "ld ra,8(sp)\n\t" \
> > + "ld s0,0(sp)\n\t" \
> > + "addi sp,sp,16\n\t" \
> > + ".option pop\n\t", \
> > + ANDESTECH_VENDOR_ID, ERRATA_ANDESTECH_NO_IOCP, \
> > + CONFIG_ERRATA_ANDES_CMO) \
> > : : "r"(_cachesize), \
> > "r"((unsigned long)(_start) & ~((_cachesize) - 1UL)), \
> > "r"((unsigned long)(_start) + (_size)), \
> > @@ -151,7 +171,7 @@ asm volatile(ALTERNATIVE_2( \
> > "r"((unsigned long)(_size)), \
> > "r"((unsigned long)(_dir)), \
> > "r"((unsigned long)(_ops)) \
> > - : "a0")
> > + : "a0", "a1", "a2", "a3", "a4", "memory")
> >
> > #define THEAD_C9XX_RV_IRQ_PMU 17
> > #define THEAD_C9XX_CSR_SCOUNTEROF 0x5c5
<snip>
> > +static int ax45mp_l2c_probe(struct platform_device *pdev)
> > +{
> > + struct device_node *np = pdev->dev.of_node;
> > + int ret;
> > +
> > + ax45mp_priv = devm_kzalloc(&pdev->dev, sizeof(*ax45mp_priv), GFP_KERNEL);
> > + if (!ax45mp_priv)
> > + return -ENOMEM;
> > +
> > + ax45mp_priv->l2c_base = devm_of_iomap(&pdev->dev, pdev->dev.of_node, 0, NULL);
> > + if (!ax45mp_priv->l2c_base) {
> > + ret = -ENOMEM;
> > + goto l2c_err;
> > + }
> > +
> > + ret = ax45mp_configure_l2_cache(np);
> > + if (ret)
> > + goto l2c_err;
> > +
> > + ret = ax45mp_configure_pma_regions(np);
> > + if (ret)
> > + goto l2c_err;
> > +
> > + static_branch_disable(&ax45mp_l2c_configured);
> > +
> > + return 0;
> > +
> > +l2c_err:
> > + devm_kfree(&pdev->dev, ax45mp_priv);
> > + ax45mp_priv = NULL;
> > + return ret;
> > +}
> > +
> > +static const struct of_device_id ax45mp_cache_ids[] = {
> > + { .compatible = "andestech,ax45mp-cache" },
> > + { /* sentinel */ }
> > +};
> > +
> > +static struct platform_driver ax45mp_l2c_driver = {
> > + .driver = {
> > + .name = "ax45mp-l2c",
> > + .of_match_table = ax45mp_cache_ids,
> > + },
> > + .probe = ax45mp_l2c_probe,
> > +};
> > +
> > +static int __init ax45mp_cache_init(void)
> > +{
> > + static_branch_enable(&ax45mp_l2c_configured);
> > + return platform_driver_register(&ax45mp_l2c_driver);
>
> the ordering is racy I think.
>
> I.e. in the function called from the cmo operations (ax45mp*_range)
> you need to access ax45mp_priv and its line-size element.
>
> But when you enable the static branch the driver is not yet registered
> but even more important, also not probed yet.
>
> So I guess the static-branch-enable should be living at the end of
> ax45mp_l2c_probe()
>
Hmm so my understanding is incorrect.

static_branch_unlikely() - evaluates to false when
static_branch_enable() is called
static_branch_unlikely() - evaluates to true when
static_branch_disable() is called

Is that what you meant?

Cheers,
Prabhakar