linux-kernel - [PATCH v5 2/5] PCI: dwc: Skip finding eDMA channels count for HDMA platforms

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Message-Id: <20240318-dw-hdma-v5-2-f04c5cdde760@linaro.org>
Date: Mon, 18 Mar 2024 11:34:26 +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>, Frank Li <Frank.Li@....com>
Subject: [PATCH v5 2/5] 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, let's 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 <fancer.lancer@...il.com>
Reviewed-by: Siddharth Vadapalli <s-vadapalli@...com>
Reviewed-by: Frank Li <Frank.Li@....com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Reviewed-by: Serge Semin <fancer.lancer@...il.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
---
 drivers/pci/controller/dwc/pcie-designware.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
index e591c1cd1efb..d17549f67e72 100644
--- a/drivers/pci/controller/dwc/pcie-designware.c
+++ b/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 ||

-- 
2.25.1