[PATCH RFC] dma: dw-edma: Fix build warning in dw_edma_pcie_probe()

[Abinash Singh <abinashlalotra@gmail.com>]

The function dw_edma_pcie_probe() in dw-edma-pcie.c triggered a
frame size warning:
ld.lld:warning:
  drivers/dma/dw-edma/dw-edma-pcie.c:162:0: stack frame size (1040) exceeds limit (1024) in function 'dw_edma_pcie_probe'

This patch reduces the stack usage by dynamically allocating the
`vsec_data` structure using kmalloc(), rather than placing it on
the stack. This eliminates the overflow warning and improves kernel
robustness.

Signed-off-by: Abinash Singh <abinashsinghlalotra@gmail.com>
---
The stack usage was further confirmed by using -fstack-usage flag.
it was usiing 928 bytes:
..............................
drivers/dma/dw-edma/dw-edma-pcie.c:377:cleanup_module   8       static
drivers/dma/dw-edma/dw-edma-pcie.c:160:dw_edma_pcie_probe       928     static
......................................
After applying the patch it becomes :
.........
drivers/dma/dw-edma/dw-edma-pcie.c:381:cleanup_module   8       static
drivers/dma/dw-edma/dw-edma-pcie.c:160:dw_edma_pcie_probe       120     static
.......

This function is used for probing . So dynamic allocation will not create
any issues.

Thank You
---
 drivers/dma/dw-edma/dw-edma-pcie.c | 60 ++++++++++++++++--------------
 1 file changed, 32 insertions(+), 28 deletions(-)

diff --git a/drivers/dma/dw-edma/dw-edma-pcie.c b/drivers/dma/dw-edma/dw-edma-pcie.c
index 49f09998e5c0..1536395eacd2 100644
--- a/drivers/dma/dw-edma/dw-edma-pcie.c
+++ b/drivers/dma/dw-edma/dw-edma-pcie.c
@@ -161,12 +161,16 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 			      const struct pci_device_id *pid)
 {
 	struct dw_edma_pcie_data *pdata = (void *)pid->driver_data;
-	struct dw_edma_pcie_data vsec_data;
+	struct dw_edma_pcie_data *vsec_data __free(kfree) = NULL;
 	struct device *dev = &pdev->dev;
 	struct dw_edma_chip *chip;
 	int err, nr_irqs;
 	int i, mask;
 
+	vsec_data = kmalloc(sizeof(*vsec_data), GFP_KERNEL);
+	if (!vsec_data)
+		return -ENOMEM;
+
 	/* Enable PCI device */
 	err = pcim_enable_device(pdev);
 	if (err) {
@@ -174,23 +178,23 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 		return err;
 	}
 
-	memcpy(&vsec_data, pdata, sizeof(struct dw_edma_pcie_data));
+	memcpy(vsec_data, pdata, sizeof(struct dw_edma_pcie_data));
 
 	/*
 	 * Tries to find if exists a PCIe Vendor-Specific Extended Capability
 	 * for the DMA, if one exists, then reconfigures it.
 	 */
-	dw_edma_pcie_get_vsec_dma_data(pdev, &vsec_data);
+	dw_edma_pcie_get_vsec_dma_data(pdev, vsec_data);
 
 	/* Mapping PCI BAR regions */
-	mask = BIT(vsec_data.rg.bar);
-	for (i = 0; i < vsec_data.wr_ch_cnt; i++) {
-		mask |= BIT(vsec_data.ll_wr[i].bar);
-		mask |= BIT(vsec_data.dt_wr[i].bar);
+	mask = BIT(vsec_data->rg.bar);
+	for (i = 0; i < vsec_data->wr_ch_cnt; i++) {
+		mask |= BIT(vsec_data->ll_wr[i].bar);
+		mask |= BIT(vsec_data->dt_wr[i].bar);
 	}
-	for (i = 0; i < vsec_data.rd_ch_cnt; i++) {
-		mask |= BIT(vsec_data.ll_rd[i].bar);
-		mask |= BIT(vsec_data.dt_rd[i].bar);
+	for (i = 0; i < vsec_data->rd_ch_cnt; i++) {
+		mask |= BIT(vsec_data->ll_rd[i].bar);
+		mask |= BIT(vsec_data->dt_rd[i].bar);
 	}
 	err = pcim_iomap_regions(pdev, mask, pci_name(pdev));
 	if (err) {
@@ -213,7 +217,7 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 		return -ENOMEM;
 
 	/* IRQs allocation */
-	nr_irqs = pci_alloc_irq_vectors(pdev, 1, vsec_data.irqs,
+	nr_irqs = pci_alloc_irq_vectors(pdev, 1, vsec_data->irqs,
 					PCI_IRQ_MSI | PCI_IRQ_MSIX);
 	if (nr_irqs < 1) {
 		pci_err(pdev, "fail to alloc IRQ vector (number of IRQs=%u)\n",
@@ -224,22 +228,22 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 	/* Data structure initialization */
 	chip->dev = dev;
 
-	chip->mf = vsec_data.mf;
+	chip->mf = vsec_data->mf;
 	chip->nr_irqs = nr_irqs;
 	chip->ops = &dw_edma_pcie_plat_ops;
 
-	chip->ll_wr_cnt = vsec_data.wr_ch_cnt;
-	chip->ll_rd_cnt = vsec_data.rd_ch_cnt;
+	chip->ll_wr_cnt = vsec_data->wr_ch_cnt;
+	chip->ll_rd_cnt = vsec_data->rd_ch_cnt;
 
-	chip->reg_base = pcim_iomap_table(pdev)[vsec_data.rg.bar];
+	chip->reg_base = pcim_iomap_table(pdev)[vsec_data->rg.bar];
 	if (!chip->reg_base)
 		return -ENOMEM;
 
 	for (i = 0; i < chip->ll_wr_cnt; i++) {
 		struct dw_edma_region *ll_region = &chip->ll_region_wr[i];
 		struct dw_edma_region *dt_region = &chip->dt_region_wr[i];
-		struct dw_edma_block *ll_block = &vsec_data.ll_wr[i];
-		struct dw_edma_block *dt_block = &vsec_data.dt_wr[i];
+		struct dw_edma_block *ll_block = &vsec_data->ll_wr[i];
+		struct dw_edma_block *dt_block = &vsec_data->dt_wr[i];
 
 		ll_region->vaddr.io = pcim_iomap_table(pdev)[ll_block->bar];
 		if (!ll_region->vaddr.io)
@@ -263,8 +267,8 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 	for (i = 0; i < chip->ll_rd_cnt; i++) {
 		struct dw_edma_region *ll_region = &chip->ll_region_rd[i];
 		struct dw_edma_region *dt_region = &chip->dt_region_rd[i];
-		struct dw_edma_block *ll_block = &vsec_data.ll_rd[i];
-		struct dw_edma_block *dt_block = &vsec_data.dt_rd[i];
+		struct dw_edma_block *ll_block = &vsec_data->ll_rd[i];
+		struct dw_edma_block *dt_block = &vsec_data->dt_rd[i];
 
 		ll_region->vaddr.io = pcim_iomap_table(pdev)[ll_block->bar];
 		if (!ll_region->vaddr.io)
@@ -298,31 +302,31 @@ static int dw_edma_pcie_probe(struct pci_dev *pdev,
 		pci_dbg(pdev, "Version:\tUnknown (0x%x)\n", chip->mf);
 
 	pci_dbg(pdev, "Registers:\tBAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p)\n",
-		vsec_data.rg.bar, vsec_data.rg.off, vsec_data.rg.sz,
+		vsec_data->rg.bar, vsec_data->rg.off, vsec_data->rg.sz,
 		chip->reg_base);
 
 
 	for (i = 0; i < chip->ll_wr_cnt; i++) {
 		pci_dbg(pdev, "L. List:\tWRITE CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
-			i, vsec_data.ll_wr[i].bar,
-			vsec_data.ll_wr[i].off, chip->ll_region_wr[i].sz,
+			i, vsec_data->ll_wr[i].bar,
+			vsec_data->ll_wr[i].off, chip->ll_region_wr[i].sz,
 			chip->ll_region_wr[i].vaddr.io, &chip->ll_region_wr[i].paddr);
 
 		pci_dbg(pdev, "Data:\tWRITE CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
-			i, vsec_data.dt_wr[i].bar,
-			vsec_data.dt_wr[i].off, chip->dt_region_wr[i].sz,
+			i, vsec_data->dt_wr[i].bar,
+			vsec_data->dt_wr[i].off, chip->dt_region_wr[i].sz,
 			chip->dt_region_wr[i].vaddr.io, &chip->dt_region_wr[i].paddr);
 	}
 
 	for (i = 0; i < chip->ll_rd_cnt; i++) {
 		pci_dbg(pdev, "L. List:\tREAD CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
-			i, vsec_data.ll_rd[i].bar,
-			vsec_data.ll_rd[i].off, chip->ll_region_rd[i].sz,
+			i, vsec_data->ll_rd[i].bar,
+			vsec_data->ll_rd[i].off, chip->ll_region_rd[i].sz,
 			chip->ll_region_rd[i].vaddr.io, &chip->ll_region_rd[i].paddr);
 
 		pci_dbg(pdev, "Data:\tREAD CH%.2u, BAR=%u, off=0x%.8lx, sz=0x%zx bytes, addr(v=%p, p=%pa)\n",
-			i, vsec_data.dt_rd[i].bar,
-			vsec_data.dt_rd[i].off, chip->dt_region_rd[i].sz,
+			i, vsec_data->dt_rd[i].bar,
+			vsec_data->dt_rd[i].off, chip->dt_region_rd[i].sz,
 			chip->dt_region_rd[i].vaddr.io, &chip->dt_region_rd[i].paddr);
 	}
 
-- 
2.43.0