linux-kernel - [PATCH 1/4] dmaengine: stm32-dma: rework irq handler to manage error before xfer events

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 20 Nov 2020 15:33:17 +0100
From:   Amelie Delaunay <amelie.delaunay@...com>
To:     Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>
CC:     <dmaengine@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Amelie Delaunay <amelie.delaunay@...com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@...com>
Subject: [PATCH 1/4] dmaengine: stm32-dma: rework irq handler to manage error before xfer events

To better understand error that can be detected by the DMA controller,
manage the error flags before the transfer flags.
This way, it is possible to know if the FIFO error flag is set for an
over/underrun condition or a FIFO level error.
When a FIFO over/underrun condition occurs, the data is not lost because
peripheral request is not acknowledged by the stream until the over/
underrun condition is cleared. If this acknowledge takes too much time,
the peripheral itself may detect an over/underrun condition of its internal
buffer and data might be lost.
That's why in case the FIFO error flag is set, we check if the channel is
disabled or not, and if a Transfer Complete flag is set, which means that
the channel is disabled because of the end of transfer.
Because channel is disabled by hardware either by a FIFO level error, or by
an end of transfer.

Signed-off-by: Amelie Delaunay <amelie.delaunay@...com>
---
 drivers/dma/stm32-dma.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index d0055d2f0b9a..55a6bd381219 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -648,21 +648,12 @@ static irqreturn_t stm32_dma_chan_irq(int irq, void *devid)
 	scr = stm32_dma_read(dmadev, STM32_DMA_SCR(chan->id));
 	sfcr = stm32_dma_read(dmadev, STM32_DMA_SFCR(chan->id));
 
-	if (status & STM32_DMA_TCI) {
-		stm32_dma_irq_clear(chan, STM32_DMA_TCI);
-		if (scr & STM32_DMA_SCR_TCIE)
-			stm32_dma_handle_chan_done(chan);
-		status &= ~STM32_DMA_TCI;
-	}
-	if (status & STM32_DMA_HTI) {
-		stm32_dma_irq_clear(chan, STM32_DMA_HTI);
-		status &= ~STM32_DMA_HTI;
-	}
 	if (status & STM32_DMA_FEI) {
 		stm32_dma_irq_clear(chan, STM32_DMA_FEI);
 		status &= ~STM32_DMA_FEI;
 		if (sfcr & STM32_DMA_SFCR_FEIE) {
-			if (!(scr & STM32_DMA_SCR_EN))
+			if (!(scr & STM32_DMA_SCR_EN) &&
+			    !(status & STM32_DMA_TCI))
 				dev_err(chan2dev(chan), "FIFO Error\n");
 			else
 				dev_dbg(chan2dev(chan), "FIFO over/underrun\n");
@@ -674,6 +665,19 @@ static irqreturn_t stm32_dma_chan_irq(int irq, void *devid)
 		if (sfcr & STM32_DMA_SCR_DMEIE)
 			dev_dbg(chan2dev(chan), "Direct mode overrun\n");
 	}
+
+	if (status & STM32_DMA_TCI) {
+		stm32_dma_irq_clear(chan, STM32_DMA_TCI);
+		if (scr & STM32_DMA_SCR_TCIE)
+			stm32_dma_handle_chan_done(chan);
+		status &= ~STM32_DMA_TCI;
+	}
+
+	if (status & STM32_DMA_HTI) {
+		stm32_dma_irq_clear(chan, STM32_DMA_HTI);
+		status &= ~STM32_DMA_HTI;
+	}
+
 	if (status) {
 		stm32_dma_irq_clear(chan, status);
 		dev_err(chan2dev(chan), "DMA error: status=0x%08x\n", status);
-- 
2.17.1