[PATCH] RISC-V: Clean up the Zicbom block size probing
Andrew Jones
ajones at ventanamicro.com
Mon Sep 5 23:38:16 PDT 2022
On Tue, Sep 06, 2022 at 08:26:57AM +0200, Andrew Jones wrote:
> From: Palmer Dabbelt <palmer at rivosinc.com>
>
> This fixes two issues: I truncated the warning's hart ID when porting to
> the 64-bit hart ID code, and the original code's warning handling could
> fire on an uninitialized hart ID.
>
> The biggest change here is that riscv_cbom_block_size is no longer
> initialized, as IMO the default isn't sane: there's nothing in the ISA
> that mandates any specific cache block size, so falling back to one will
> just silently produce the wrong answer on some systems. This also
> changes the probing order so the cache block size is known before
> enabling Zicbom support.
>
> Fixes: 3aefb2ee5bdd ("riscv: implement Zicbom-based CMO instructions + the t-head variant")
> Fixes: 1631ba1259d6 ("riscv: Add support for non-coherent devices using zicbom extension")
> Reported-by: kernel test robot <lkp at intel.com>
> Signed-off-by: Palmer Dabbelt <palmer at rivosinc.com>
> Reviewed-by: Conor Dooley <conor.dooley at microchip.com>
> [Applied Conor Dooley's and Heiko Stuebner's changes.]
> Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
> ---
> arch/riscv/errata/thead/errata.c | 1 +
> arch/riscv/kernel/setup.c | 2 +-
> arch/riscv/mm/dma-noncoherent.c | 23 +++++++++++++----------
> 3 files changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
> index 202c83f677b2..96648c176f37 100644
> --- a/arch/riscv/errata/thead/errata.c
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -37,6 +37,7 @@ static bool errata_probe_cmo(unsigned int stage,
> if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> return false;
>
> + riscv_cbom_block_size = L1_CACHE_BYTES;
Darn, of course this doesn't compile independently of Anup's move change.
I should have done the move first as Heiko suggested.
I'll try again by posting both Anup's move change and this patch
rebased on Anup's.
Thanks,
drew
> riscv_noncoherent_supported();
> return true;
> #else
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index 95ef6e2bf45c..2dfc463b86bb 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -296,8 +296,8 @@ void __init setup_arch(char **cmdline_p)
> setup_smp();
> #endif
>
> - riscv_fill_hwcap();
> riscv_init_cbom_blocksize();
> + riscv_fill_hwcap();
> apply_boot_alternatives();
> }
>
> diff --git a/arch/riscv/mm/dma-noncoherent.c b/arch/riscv/mm/dma-noncoherent.c
> index cd2225304c82..8a49ea5ba01d 100644
> --- a/arch/riscv/mm/dma-noncoherent.c
> +++ b/arch/riscv/mm/dma-noncoherent.c
> @@ -12,7 +12,7 @@
> #include <linux/of_device.h>
> #include <asm/cacheflush.h>
>
> -static unsigned int riscv_cbom_block_size = L1_CACHE_BYTES;
> +static unsigned int riscv_cbom_block_size;
> static bool noncoherent_supported;
>
> void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
> @@ -79,38 +79,41 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
> void riscv_init_cbom_blocksize(void)
> {
> struct device_node *node;
> + unsigned long cbom_hartid;
> + u32 val, probed_block_size;
> int ret;
> - u32 val;
>
> + probed_block_size = 0;
> for_each_of_cpu_node(node) {
> unsigned long hartid;
> - int cbom_hartid;
>
> ret = riscv_of_processor_hartid(node, &hartid);
> if (ret)
> continue;
>
> - if (hartid < 0)
> - continue;
> -
> /* set block-size for cbom extension if available */
> ret = of_property_read_u32(node, "riscv,cbom-block-size", &val);
> if (ret)
> continue;
>
> - if (!riscv_cbom_block_size) {
> - riscv_cbom_block_size = val;
> + if (!probed_block_size) {
> + probed_block_size = val;
> cbom_hartid = hartid;
> } else {
> - if (riscv_cbom_block_size != val)
> - pr_warn("cbom-block-size mismatched between harts %d and %lu\n",
> + if (probed_block_size != val)
> + pr_warn("cbom-block-size mismatched between harts %lu and %lu\n",
> cbom_hartid, hartid);
> }
> }
> +
> + if (probed_block_size)
> + riscv_cbom_block_size = probed_block_size;
> }
> #endif
>
> void riscv_noncoherent_supported(void)
> {
> + WARN(!riscv_cbom_block_size,
> + "Non-coherent DMA support enabled without a block size\n");
> noncoherent_supported = true;
> }
> --
> 2.37.2
>
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