linux-kernel - [PATCH 11/21] mips: dma-mapping: skip invalidating before bidirectional DMA

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Message-Id: <20230327121317.4081816-12-arnd@kernel.org>
Date:   Mon, 27 Mar 2023 14:13:07 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     Arnd Bergmann <arnd@...db.de>, Vineet Gupta <vgupta@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
        Brian Cain <bcain@...cinc.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michal Simek <monstr@...str.eu>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Stafford Horne <shorne@...il.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Rich Felker <dalias@...c.org>,
        John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,
        "David S. Miller" <davem@...emloft.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Christoph Hellwig <hch@....de>,
        Robin Murphy <robin.murphy@....com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-oxnas@...ups.io,
        linux-csky@...r.kernel.org, linux-hexagon@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-openrisc@...r.kernel.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org
Subject: [PATCH 11/21] mips: dma-mapping: skip invalidating before bidirectional DMA

From: Arnd Bergmann <arnd@...db.de>

Some architectures that need to invalidate buffers after bidirectional
DMA because of speculative prefetching only do a simpler writeback
before that DMA, while architectures that don't need to do the second
invalidate tend to have a combined writeback+invalidate before the
DMA.

The behavior on mips is slightly inconsistent, as it always
does the invalidation before bidirectional DMA and conditionally
does it a second time.

In order to make the behavior the same as the rest, change it
so that there is exactly one invalidation here, either before
or after the DMA.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/mips/mm/dma-noncoherent.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/mips/mm/dma-noncoherent.c b/arch/mips/mm/dma-noncoherent.c
index 3c4fc97b9f39..b4350faf4f1e 100644
--- a/arch/mips/mm/dma-noncoherent.c
+++ b/arch/mips/mm/dma-noncoherent.c
@@ -65,7 +65,11 @@ static inline void dma_sync_virt_for_device(void *addr, size_t size,
 		dma_cache_inv((unsigned long)addr, size);
 		break;
 	case DMA_BIDIRECTIONAL:
-		dma_cache_wback_inv((unsigned long)addr, size);
+		if (IS_ENABLED(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) &&
+		    cpu_needs_post_dma_flush())
+			dma_cache_wback((unsigned long)addr, size);
+		else
+			dma_cache_wback_inv((unsigned long)addr, size);
 		break;
 	default:
 		BUG();
-- 
2.39.2