PCI: dwc: Skip finding eDMA channels count for HDMA platforms

In the case of Hyper DMA (HDMA) present in DWC controllers, there is no way
the drivers can auto detect the number of read/write channels as like its
predecessor embedded DMA (eDMA). So the glue drivers making use of HDMA
have to pass the channels count during probe.

To accommodate that, skip the existing auto detection of channels count
procedure for HDMA based platforms. If the channels count passed by the
glue drivers were wrong in any form, then the existing sanity check will
catch it.

Suggested-by: Serge Semin <[email protected]>
Link: https://lore.kernel.org/linux-pci/[email protected]
Signed-off-by: Manivannan Sadhasivam <[email protected]>
Signed-off-by: Krzysztof Wilczyński <[email protected]>
Signed-off-by: Bjorn Helgaas <[email protected]>
Reviewed-by: Frank Li <[email protected]>
Reviewed-by: Serge Semin <[email protected]>
Reviewed-by: Siddharth Vadapalli <[email protected]>
Reviewed-by: Yoshihiro Shimoda <[email protected]>

Author: Mani-Sadhasivam

drivers/pci/controller/dwc/pcie-designware.c

@@ -927,10 +927,18 @@ static int dw_pcie_edma_find_channels(struct dw_pcie *pci)
 {
 	u32 val;
 
-	val = dw_pcie_readl_dma(pci, PCIE_DMA_CTRL);
+	/*
+	 * Autodetect the read/write channels count only for non-HDMA platforms.
+	 * HDMA platforms with native CSR mapping doesn't support autodetect,
+	 * so the glue drivers should've passed the valid count already. If not,
+	 * the below sanity check will catch it.
+	 */
+	if (pci->edma.mf != EDMA_MF_HDMA_NATIVE) {
+		val = dw_pcie_readl_dma(pci, PCIE_DMA_CTRL);
 
-	pci->edma.ll_wr_cnt = FIELD_GET(PCIE_DMA_NUM_WR_CHAN, val);
-	pci->edma.ll_rd_cnt = FIELD_GET(PCIE_DMA_NUM_RD_CHAN, val);
+		pci->edma.ll_wr_cnt = FIELD_GET(PCIE_DMA_NUM_WR_CHAN, val);
+		pci->edma.ll_rd_cnt = FIELD_GET(PCIE_DMA_NUM_RD_CHAN, val);
+	}
 
 	/* Sanity check the channels count if the mapping was incorrect */
 	if (!pci->edma.ll_wr_cnt || pci->edma.ll_wr_cnt > EDMA_MAX_WR_CH ||