Re: [PATCH v7 5/9] PCI: dwc: Avoid reading a register to detect whether eDMA exists

From: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Cc: lpieralisi@kernel.org, robh+dt@kernel.org, kw@linux.com,
	bhelgaas@google.com, krzk+dt@kernel.org,
	marek.vasut+renesas@gmail.com, linux-pci@vger.kernel.org,
	devicetree@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
	fancer.lancer@gmail.com, Sergey.Semin@baikalelectronics.ru
Subject: Re: [PATCH v7 5/9] PCI: dwc: Avoid reading a register to detect whether eDMA exists
Date: Tue, 22 Nov 2022 19:25:50 +0530	[thread overview]
Message-ID: <20221122135550.GD157542@thinkpad> (raw)
In-Reply-To: <20221121124400.1282768-6-yoshihiro.shimoda.uh@renesas.com>

+ Serge (who authored EDMA support)

Thanks,
Mani

On Mon, Nov 21, 2022 at 09:43:56PM +0900, Yoshihiro Shimoda wrote:
> Since reading value of PCIE_DMA_VIEWPORT_BASE + PCIE_DMA_CTRL was
> 0x00000000 on one of SoCs (R-Car S4-8), it cannot find the eDMA.
> So, directly read the eDMA register if edma.reg_base is not zero.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 637d01807c67..2cc8584da6f4 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -836,8 +836,7 @@ static int dw_pcie_edma_find_chip(struct dw_pcie *pci)
>  {
>  	u32 val;
>  
> -	val = dw_pcie_readl_dbi(pci, PCIE_DMA_VIEWPORT_BASE + PCIE_DMA_CTRL);
> -	if (val == 0xFFFFFFFF && pci->edma.reg_base) {
> +	if (pci->edma.reg_base) {
>  		pci->edma.mf = EDMA_MF_EDMA_UNROLL;
>  
>  		val = dw_pcie_readl_dma(pci, PCIE_DMA_CTRL);
> @@ -845,6 +844,7 @@ static int dw_pcie_edma_find_chip(struct dw_pcie *pci)
>  		pci->edma.mf = EDMA_MF_EDMA_LEGACY;
>  
>  		pci->edma.reg_base = pci->dbi_base + PCIE_DMA_VIEWPORT_BASE;
> +		val = dw_pcie_readl_dbi(pci, PCIE_DMA_VIEWPORT_BASE + PCIE_DMA_CTRL);
>  	} else {
>  		return -ENODEV;
>  	}
> -- 
> 2.25.1
> 

-- 
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