FAILED: patch "[PATCH] ARC: dma [non IOC]: fix arc_dma_sync_single_for_(device|cpu)" failed to apply to 4.17-stable tree

From 4c612add7b18844ddd733ebdcbe754520155999b Mon Sep 17 00:00:00 2001

The patch below does not apply to the 4.17-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 4c612add7b18844ddd733ebdcbe754520155999b Mon Sep 17 00:00:00 2001
From: Eugeniy Paltsev <[email protected]>
Date: Tue, 24 Jul 2018 17:13:02 +0300
Subject: [PATCH] ARC: dma [non IOC]: fix arc_dma_sync_single_for_(device|cpu)

ARC backend for dma_sync_single_for_(device|cpu) was broken as it was not honoring the @dir argument and simply forcing it based on the call:
- arc_dma_sync_single_for_device(dir) assumed DMA_TO_DEVICE (cache wback)
- arc_dma_sync_single_for_cpu(dir) assumed DMA_FROM_DEVICE (cache inv)

This is not true given the DMA API programming model and has been discussed here [1] in some detail.

Interestingly while the deficiency has been there forever, it only started showing up after 4.17 dma common ops rework, commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page") which wired up these calls under the more commonly used dma_map_page API triggering the issue.

[1]: https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2018_5_18_979&d=DwIDAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=c14YS-cH-kdhTOW89KozFhBtBJgs1zXscZojEZQ0THs&m=7aV-FuW2twpiMTknC5mcDf1AngIn1HqXHwIhZoysGW4&s=EeRw-AeiwFbuvEid0L-9vik7eJbDwyNrwCjmcHVSSyo&e=

Fixes commit a8eb92d02dd7 ("arc: fix arc_dma_{map,unmap}_page")

Cc [email protected] # v4.17+

Signed-off-by Eugeniy Paltsev <[email protected]>

Signed-off-by Vineet Gupta <[email protected]>

[vgupta: reworked changelog]

arch/arc/mm/dma.c +47 -2

index 8c1071840979..ec47e6079f5d 100644
@@ -129,14 +129,59 @@ int arch_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 	return ret;
 }
 
+/*
+ * Cache operations depending on function and direction argument, inspired by
+ * https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2018_5_18_979&d=DwIDAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=c14YS-cH-kdhTOW89KozFhBtBJgs1zXscZojEZQ0THs&m=7aV-FuW2twpiMTknC5mcDf1AngIn1HqXHwIhZoysGW4&s=EeRw-AeiwFbuvEid0L-9vik7eJbDwyNrwCjmcHVSSyo&e=
+ * "dma_sync_*_for_cpu and direction=TO_DEVICE (was Re: [PATCH 02/20]
+ * dma-mapping: provide a generic dma-noncoherent implementation)"
+ *
+ *          |   map          ==  for_device     |   unmap     ==  for_cpu
+ *          |----------------------------------------------------------------
+ * TO_DEV   |   writeback        writeback      |   none          none
+ * FROM_DEV |   invalidate       invalidate     |   invalidate*   invalidate*
+ * BIDIR    |   writeback+inv    writeback+inv  |   invalidate    invalidate
+ *
+ *     [*] needed for CPU speculative prefetches
+ *
+ * NOTE: we don't check the validity of direction argument as it is done in
+ * upper layer functions (in include/linux/dma-mapping.h)
+ */
+
 void arch_sync_dma_for_device(struct device *dev, phys_addr_t paddr,
 		size_t size, enum dma_data_direction dir)
 {
-	dma_cache_wback(paddr, size);
+	switch (dir) {
+	case DMA_TO_DEVICE:
+		dma_cache_wback(paddr, size);
+		break;
+
+	case DMA_FROM_DEVICE:
+		dma_cache_inv(paddr, size);
+		break;
+
+	case DMA_BIDIRECTIONAL:
+		dma_cache_wback_inv(paddr, size);
+		break;
+
+	default:
+		break;
+	}
 }
 
 void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
 		size_t size, enum dma_data_direction dir)
 {
-	dma_cache_inv(paddr, size);
+	switch (dir) {
+	case DMA_TO_DEVICE:
+		break;
+
+	/* FROM_DEVICE invalidate needed if speculative CPU prefetch only */
+	case DMA_FROM_DEVICE:
+	case DMA_BIDIRECTIONAL:
+		dma_cache_inv(paddr, size);
+		break;
+
+	default:
+		break;
+	}
 }