linux-kernel - [PATCH 3.16 02/47] ARM: riscpc: fix DMA

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Message-ID: <lsq.1572026582.925593706@decadent.org.uk>
Date:   Fri, 25 Oct 2019 19:03:03 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Russell King" <rmk+kernel@...linux.org.uk>
Subject: [PATCH 3.16 02/47] ARM: riscpc: fix DMA

3.16.76-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Russell King <rmk+kernel@...linux.org.uk>

commit ffd9a1ba9fdb7f2bd1d1ad9b9243d34e96756ba2 upstream.

DMA got broken a while back in two different ways:
1) a change in the behaviour of disable_irq() to wait for the interrupt
   to finish executing causes us to deadlock at the end of DMA.
2) a change to avoid modifying the scatterlist left the first transfer
   uninitialised.

DMA is only used with expansion cards, so has gone unnoticed.

Fixes: fa4e99899932 ("[ARM] dma: RiscPC: don't modify DMA SG entries")
Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/arm/mach-rpc/dma.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/arch/arm/mach-rpc/dma.c
+++ b/arch/arm/mach-rpc/dma.c
@@ -131,7 +131,7 @@ static irqreturn_t iomd_dma_handle(int i
 	} while (1);
 
 	idma->state = ~DMA_ST_AB;
-	disable_irq(irq);
+	disable_irq_nosync(irq);
 
 	return IRQ_HANDLED;
 }
@@ -174,6 +174,9 @@ static void iomd_enable_dma(unsigned int
 				DMA_FROM_DEVICE : DMA_TO_DEVICE);
 		}
 
+		idma->dma_addr = idma->dma.sg->dma_address;
+		idma->dma_len = idma->dma.sg->length;
+
 		iomd_writeb(DMA_CR_C, dma_base + CR);
 		idma->state = DMA_ST_AB;
 	}