linux-kernel - Re: [PATCH v10 2/3] PCI: dwc: intel: PCIe RC controller driver

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Date:   Wed, 11 Dec 2019 08:20:22 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Dilip Kota <eswara.kota@...ux.intel.com>
Cc:     lorenzo.pieralisi@....com, linux-pci@...r.kernel.org,
        devicetree@...r.kernel.org, andriy.shevchenko@...el.com,
        gustavo.pimentel@...opsys.com, andrew.murray@....com,
        robh@...nel.org, linux-kernel@...r.kernel.org,
        cheol.yong.kim@...el.com, chuanhua.lei@...ux.intel.com,
        qi-ming.wu@...el.com
Subject: Re: [PATCH v10 2/3] PCI: dwc: intel: PCIe RC controller driver

On Wed, Dec 11, 2019 at 05:59:58PM +0800, Dilip Kota wrote:
> 
> On 12/11/2019 7:49 AM, Bjorn Helgaas wrote:
> > On Fri, Dec 06, 2019 at 03:27:49PM +0800, Dilip Kota wrote:
> > > Add support to PCIe RC controller on Intel Gateway SoCs.
> > > PCIe controller is based of Synopsys DesignWare PCIe core.
> > > 
> > > Intel PCIe driver requires Upconfigure support, Fast Training
> > > Sequence and link speed configurations. So adding the respective
> > > helper functions in the PCIe DesignWare framework.
> > > It also programs hardware autonomous speed during speed
> > > configuration so defining it in pci_regs.h.
> > > 
> > > Also, mark Intel PCIe driver depends on MSI IRQ Domain
> > > as Synopsys DesignWare framework depends on the
> > > PCI_MSI_IRQ_DOMAIN.
> > > 
> > > Signed-off-by: Dilip Kota <eswara.kota@...ux.intel.com>
> > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> > > Reviewed-by: Andrew Murray <andrew.murray@....com>
> > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@...el.com>
> > > Acked-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>

> > > +static void pcie_update_bits(void __iomem *base, u32 ofs, u32 mask, u32 val)
> > > +{
> > > +	u32 old;
> > > +
> > > +	old = readl(base + ofs);
> > > +	val = (old & ~mask) | (val & mask);
> > > +
> > > +	if (val != old)
> > > +		writel(val, base + ofs);
> > I assume this is never used on registers where the "old & ~mask" part
> > contains RW1C bits?  If there are RW1C bits in that part, this will
> > corrupt them.
> There is no impact because RW1C bits of respective registers are 0s at the
> time of this function call.

Sounds ... dangerous, but I'll take your word for it.

> I see, this patch series is merged in the maintainer tree.
> Should i need to submit as a separate patch on top of maintainer tree or
> submit the new version of whole patch series?
> Please let me know the best practice.

Sorry, I didn't realize this had already been merged to Lorenzo's
tree.  But it's not upstream (in Linus' tree) yet.  I don't know how
Andrew and Lorenzo want to handle this.  None of these are important,
so you could just ignore these comments.

What I personally would do is rebase the branch, e.g.,
lpieralisi/pci/dwc, and apply an incremental patch.  But it's up to
Andrew and Lorenzo whether they want to do anything.

Bjorn