linux-kernel - [PATCH AUTOSEL 5.4 11/17] parisc: Improve cache flushing for PCXL in arch_sync_dma_for

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Date:   Wed, 31 May 2023 09:44:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Helge Deller <deller@....de>, Sasha Levin <sashal@...nel.org>,
        James.Bottomley@...senPartnership.com, gaoxin@...rlc.com,
        linux-parisc@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 11/17] parisc: Improve cache flushing for PCXL in arch_sync_dma_for_cpu()

From: Helge Deller <deller@....de>

[ Upstream commit 59fa12646d9f56c842b4d5b6418ed77af625c588 ]

Add comment in arch_sync_dma_for_device() and handle the direction flag in
arch_sync_dma_for_cpu().

When receiving data from the device (DMA_FROM_DEVICE) unconditionally
purge the data cache in arch_sync_dma_for_cpu().

Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/parisc/kernel/pci-dma.c | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/parisc/kernel/pci-dma.c b/arch/parisc/kernel/pci-dma.c
index a60d47fd4d55f..1621f678aa05b 100644
--- a/arch/parisc/kernel/pci-dma.c
+++ b/arch/parisc/kernel/pci-dma.c
@@ -442,13 +442,29 @@ void arch_dma_free(struct device *dev, size_t size, void *vaddr,
 void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
 		enum dma_data_direction dir)
 {
+	/*
+	 * fdc: The data cache line is written back to memory, if and only if
+	 * it is dirty, and then invalidated from the data cache.
+	 */
 	flush_kernel_dcache_range((unsigned long)phys_to_virt(paddr), size);
 }
 
 void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
 		enum dma_data_direction dir)
 {
-	flush_kernel_dcache_range((unsigned long)phys_to_virt(paddr), size);
+	unsigned long addr = (unsigned long) phys_to_virt(paddr);
+
+	switch (dir) {
+	case DMA_TO_DEVICE:
+	case DMA_BIDIRECTIONAL:
+		flush_kernel_dcache_range(addr, size);
+		return;
+	case DMA_FROM_DEVICE:
+		purge_kernel_dcache_range_asm(addr, addr + size);
+		return;
+	default:
+		BUG();
+	}
 }
 
 void arch_dma_cache_sync(struct device *dev, void *vaddr, size_t size,
-- 
2.39.2