linux-kernel - [PATCH v3 2/5] PCI: dwc: Skip finding eDMA channels count if glue drivers have passed them

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Date: Mon, 26 Feb 2024 17:07:27 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Jingoo Han <jingoohan1@...il.com>, 
 Gustavo Pimentel <gustavo.pimentel@...opsys.com>, 
 Lorenzo Pieralisi <lpieralisi@...nel.org>, 
 Krzysztof Wilczyński <kw@...ux.com>, 
 Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
 Marek Vasut <marek.vasut+renesas@...il.com>, 
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>, 
 Kishon Vijay Abraham I <kishon@...nel.org>
Cc: Serge Semin <fancer.lancer@...il.com>, linux-pci@...r.kernel.org, 
 linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, mhi@...ts.linux.dev, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Siddharth Vadapalli <s-vadapalli@...com>
Subject: [PATCH v3 2/5] PCI: dwc: Skip finding eDMA channels count if glue
 drivers have passed them

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, let's skip finding the channels if the channels count
were already passed by glue drivers. If the channels count passed were
wrong in any form, then the existing sanity check will catch it.

Suggested-by: Serge Semin <fancer.lancer@...il.com>
Reviewed-by: Siddharth Vadapalli <s-vadapalli@...com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index 193fcd86cf93..ce273c3c5421 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/drivers/pci/controller/dwc/pcie-designware.c
@@ -927,13 +927,15 @@ static int dw_pcie_edma_find_channels(struct dw_pcie *pci)
 {
 	u32 val;
 
-	if (pci->edma.mf == EDMA_MF_EDMA_LEGACY)
-		val = dw_pcie_readl_dbi(pci, PCIE_DMA_VIEWPORT_BASE + PCIE_DMA_CTRL);
-	else
-		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);
+	if (!pci->edma.ll_wr_cnt || !pci->edma.ll_rd_cnt) {
+		if (pci->edma.mf == EDMA_MF_EDMA_LEGACY)
+			val = dw_pcie_readl_dbi(pci, PCIE_DMA_VIEWPORT_BASE + PCIE_DMA_CTRL);
+		else
+			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);
+	}
 
 	/* 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 ||

-- 
2.25.1