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

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Date: Wed, 21 Feb 2024 11:04:57 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Siddharth Vadapalli <s-vadapalli@...com>
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
Subject: Re: [PATCH v2 1/5] PCI: dwc: Refactor dw_pcie_edma_find_chip() API

On Tue, Feb 20, 2024 at 05:41:41PM +0530, Siddharth Vadapalli wrote:
> 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?
> 

Yes indeed. Actually, EDMA_MF_EDMA_LEGACY is the default mapping format (because
its value is 0x0), but setting it explicitly would also make sense.

- Mani

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