linux-kernel - [PATCH v3 07/15] dmaengine: dw-edma: Improve number of channels check

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Message-Id: <c70f23ba8cb76facbb620bbad2814b29209db6b9.1612374941.git.gustavo.pimentel@synopsys.com>
Date:   Wed,  3 Feb 2021 18:56:59 +0100
From:   Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
To:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        dmaengine@...r.kernel.org, Vinod Koul <vkoul@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
Subject: [PATCH v3 07/15] dmaengine: dw-edma: Improve number of channels check

It was added some extra checks to ensure that the driver doesn't try to
use more DMA channels than actually are available in hardware.

Signed-off-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>
---
 drivers/dma/dw-edma/dw-edma-core.c | 21 +++++++++------------
 drivers/dma/dw-edma/dw-edma-core.h |  2 ++
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index 0fe3835..5495cf7 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -914,19 +914,16 @@ int dw_edma_probe(struct dw_edma_chip *chip)
 
 	raw_spin_lock_init(&dw->lock);
 
-	if (!dw->wr_ch_cnt) {
-		/* Find out how many write channels are supported by hardware */
-		dw->wr_ch_cnt = dw_edma_v0_core_ch_count(dw, EDMA_DIR_WRITE);
-		if (!dw->wr_ch_cnt)
-			return -EINVAL;
-	}
+	dw->wr_ch_cnt = min_t(u16, dw->wr_ch_cnt,
+			      dw_edma_v0_core_ch_count(dw, EDMA_DIR_WRITE));
+	dw->wr_ch_cnt = min_t(u16, dw->wr_ch_cnt, EDMA_MAX_WR_CH);
 
-	if (!dw->rd_ch_cnt) {
-		/* Find out how many read channels are supported by hardware */
-		dw->rd_ch_cnt = dw_edma_v0_core_ch_count(dw, EDMA_DIR_READ);
-		if (!dw->rd_ch_cnt)
-			return -EINVAL;
-	}
+	dw->rd_ch_cnt = min_t(u16, dw->rd_ch_cnt,
+			      dw_edma_v0_core_ch_count(dw, EDMA_DIR_READ));
+	dw->rd_ch_cnt = min_t(u16, dw->rd_ch_cnt, EDMA_MAX_RD_CH);
+
+	if (!dw->wr_ch_cnt && !dw->rd_ch_cnt)
+		return -EINVAL;
 
 	dev_vdbg(dev, "Channels:\twrite=%d, read=%d\n",
 		 dw->wr_ch_cnt, dw->rd_ch_cnt);
diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h
index f72ebaa..650b1c7 100644
--- a/drivers/dma/dw-edma/dw-edma-core.h
+++ b/drivers/dma/dw-edma/dw-edma-core.h
@@ -15,6 +15,8 @@
 #include "../virt-dma.h"
 
 #define EDMA_LL_SZ					24
+#define EDMA_MAX_WR_CH					8
+#define EDMA_MAX_RD_CH					8
 
 enum dw_edma_dir {
 	EDMA_DIR_WRITE = 0,
-- 
2.7.4