linux-kernel - Re: [PATCH v2 1/5] PCI: dwc: Refactor dw_pcie_edma_find

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Date: Tue, 20 Feb 2024 17:41:41 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
CC: 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>,
        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>,
        <s-vadapalli@...com>
Subject: Re: [PATCH v2 1/5] PCI: dwc: Refactor dw_pcie_edma_find_chip() API

On 24/02/16 11:04PM, Manivannan Sadhasivam wrote:
> In order to add support for Hyper DMA (HDMA), let's refactor the existing
> dw_pcie_edma_find_chip() API by moving the common code to separate
> functions.
> 
> No functional change.
> 
> Suggested-by: Serge Semin <fancer.lancer@...il.com>
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> ---
>  drivers/pci/controller/dwc/pcie-designware.c | 40 +++++++++++++++++++++++-----
>  1 file changed, 33 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-designware.c b/drivers/pci/controller/dwc/pcie-designware.c
> index 250cf7f40b85..3a26dfc5368f 100644
> --- a/drivers/pci/controller/dwc/pcie-designware.c
> +++ b/drivers/pci/controller/dwc/pcie-designware.c
> @@ -880,7 +880,17 @@ static struct dw_edma_plat_ops dw_pcie_edma_ops = {
>  	.irq_vector = dw_pcie_edma_irq_vector,
>  };
>  
> -static int dw_pcie_edma_find_chip(struct dw_pcie *pci)
> +static void dw_pcie_edma_init_data(struct dw_pcie *pci)
> +{
> +	pci->edma.dev = pci->dev;
> +
> +	if (!pci->edma.ops)
> +		pci->edma.ops = &dw_pcie_edma_ops;
> +
> +	pci->edma.flags |= DW_EDMA_CHIP_LOCAL;
> +}
> +
> +static int dw_pcie_edma_find_mf(struct dw_pcie *pci)
>  {
>  	u32 val;
>  
> @@ -902,8 +912,6 @@ static int dw_pcie_edma_find_chip(struct dw_pcie *pci)
>  
>  	if (val == 0xFFFFFFFF && pci->edma.reg_base) {
>  		pci->edma.mf = EDMA_MF_EDMA_UNROLL;
> -
> -		val = dw_pcie_readl_dma(pci, PCIE_DMA_CTRL);
>  	} else if (val != 0xFFFFFFFF) {
>  		pci->edma.mf = EDMA_MF_EDMA_LEGACY;

Minor suggestion:

The above section prior to this patch was:
	if (val == 0xFFFFFFFF && pci->edma.reg_base) {
		pci->edma.mf = EDMA_MF_EDMA_UNROLL;

		val = dw_pcie_readl_dma(pci, PCIE_DMA_CTRL);
	} else if (val != 0xFFFFFFFF) {
		pci->edma.mf = EDMA_MF_EDMA_LEGACY;

		pci->edma.reg_base = pci->dbi_base + PCIE_DMA_VIEWPORT_BASE;
	} else {
		return -ENODEV;
	}

And this patch is removing the call to dw_pcie_readl_dma() in the "if"
condition above. So the curly braces after this patch will only be
present because of the "else if" statement. So is the following change a
good idea?

	/* Assume it is EDMA_LEGACY by default but update it later if needed */
	pci->edma.mf = EDMA_MF_EDMA_LEGACY;

	if (val == 0xFFFFFFFF && pci->edma.reg_base)
		pci->edma.mf = EDMA_MF_EDMA_UNROLL;
	else if (val != 0xFFFFFFFF)
		pci->edma.reg_base = pci->dbi_base + PCIE_DMA_VIEWPORT_BASE;
	else
		return -ENODEV;


Regards,
Siddharth.