[PATCH v2][next] dmaengine: dw-edma: Check MSI descriptor before copying

[Alan Mikhak <alan.mikhak@sifive.com>]

From: Alan Mikhak <alan.mikhak@sifive.com>

Modify dw_edma_irq_request() to check if a struct msi_desc entry exists
before copying the contents of its struct msi_msg pointer.

Without this sanity check, __get_cached_msi_msg() crashes when invoked by
dw_edma_irq_request() running on a Linux-based PCIe endpoint device. MSI
interrupt are not received by PCIe endpoint devices. If irq_get_msi_desc()
returns null, then there is no cached struct msi_msg to be copied.

This patch depends on the following patch:
[PATCH v2] dmaengine: dw-edma: Decouple dw-edma-core.c from struct pci_dev
https://patchwork.kernel.org/patch/11491757/

Rebased on linux-next which has above patch applied.

Fixes: Build error with config x86_64-randconfig-f003-20200422
Fixes: Build error with config s390-allmodconfig
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
---
 drivers/dma/dw-edma/dw-edma-core.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
index db401eb11322..306ab50462be 100644
--- a/drivers/dma/dw-edma/dw-edma-core.c
+++ b/drivers/dma/dw-edma/dw-edma-core.c
@@ -13,6 +13,7 @@
 #include <linux/dmaengine.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/dma/edma.h>
 #include <linux/dma-mapping.h>
 
@@ -773,6 +774,7 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 	u32 rd_mask = 1;
 	int i, err = 0;
 	u32 ch_cnt;
+	int irq;
 
 	ch_cnt = dw->wr_ch_cnt + dw->rd_ch_cnt;
 
@@ -781,16 +783,16 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 
 	if (dw->nr_irqs == 1) {
 		/* Common IRQ shared among all channels */
-		err = request_irq(dw->ops->irq_vector(dev, 0),
-				  dw_edma_interrupt_common,
+		irq = dw->ops->irq_vector(dev, 0);
+		err = request_irq(irq, dw_edma_interrupt_common,
 				  IRQF_SHARED, dw->name, &dw->irq[0]);
 		if (err) {
 			dw->nr_irqs = 0;
 			return err;
 		}
 
-		get_cached_msi_msg(dw->ops->irq_vector(dev, 0),
-				   &dw->irq[0].msi);
+		if (irq_get_msi_desc(irq))
+			get_cached_msi_msg(irq, &dw->irq[0].msi);
 	} else {
 		/* Distribute IRQs equally among all channels */
 		int tmp = dw->nr_irqs;
@@ -804,7 +806,8 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 		dw_edma_add_irq_mask(&rd_mask, *rd_alloc, dw->rd_ch_cnt);
 
 		for (i = 0; i < (*wr_alloc + *rd_alloc); i++) {
-			err = request_irq(dw->ops->irq_vector(dev, i),
+			irq = dw->ops->irq_vector(dev, i);
+			err = request_irq(irq,
 					  i < *wr_alloc ?
 						dw_edma_interrupt_write :
 						dw_edma_interrupt_read,
@@ -815,8 +818,8 @@ static int dw_edma_irq_request(struct dw_edma_chip *chip,
 				return err;
 			}
 
-			get_cached_msi_msg(dw->ops->irq_vector(dev, i),
-					   &dw->irq[i].msi);
+			if (irq_get_msi_desc(irq))
+				get_cached_msi_msg(irq, &dw->irq[i].msi);
 		}
 
 		dw->nr_irqs = i;
-- 
2.7.4