linux-kernel - Re: [PATCH v8 03/10] PCI: dwc: ep: Introduce dw_pcie_ep_cleanup() API for drivers supporting PERST#

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Date: Mon, 4 Mar 2024 13:47:13 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Niklas Cassel <cassel@...nel.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>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Kishon Vijay Abraham I <kishon@...com>,
	Vidya Sagar <vidyas@...dia.com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Richard Zhu <hongxing.zhu@....com>,
	Lucas Stach <l.stach@...gutronix.de>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	NXP Linux Team <linux-imx@....com>,
	Minghuan Lian <minghuan.Lian@....com>,
	Mingkai Hu <mingkai.hu@....com>, Roy Zang <roy.zang@....com>,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Kishon Vijay Abraham I <kishon@...nel.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-tegra@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v8 03/10] PCI: dwc: ep: Introduce dw_pcie_ep_cleanup()
 API for drivers supporting PERST#

On Thu, Feb 29, 2024 at 01:40:29PM +0100, Niklas Cassel wrote:
> On Sat, Feb 24, 2024 at 12:24:09PM +0530, Manivannan Sadhasivam wrote:
> > For DWC glue drivers supporting PERST# (currently Qcom and Tegra194), some
> > of the DWC resources like eDMA should be cleaned up during the PERST#
> > assert time.
> > 
> > So let's introduce a dw_pcie_ep_cleanup() API that could be called by these
> > drivers to cleanup the DWC specific resources. Currently, it just removes
> > eDMA.
> > 
> > Reported-by: Niklas Cassel <cassel@...nel.org>
> > Closes: https://lore.kernel.org/linux-pci/ZWYmX8Y%2F7Q9WMxES@x1-carbon
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware-ep.c | 11 +++++++++--
> >  drivers/pci/controller/dwc/pcie-designware.h    |  5 +++++
> >  drivers/pci/controller/dwc/pcie-qcom-ep.c       |  1 +
> >  drivers/pci/controller/dwc/pcie-tegra194.c      |  2 ++
> >  4 files changed, 17 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/dwc/pcie-designware-ep.c b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > index 2b11290aab4c..1205bfba8310 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware-ep.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware-ep.c
> > @@ -564,12 +564,19 @@ int dw_pcie_ep_raise_msix_irq(struct dw_pcie_ep *ep, u8 func_no,
> >  	return 0;
> >  }
> >  
> > -void dw_pcie_ep_deinit(struct dw_pcie_ep *ep)
> > +void dw_pcie_ep_cleanup(struct dw_pcie_ep *ep)
> >  {
> >  	struct dw_pcie *pci = to_dw_pcie_from_ep(ep);
> > -	struct pci_epc *epc = ep->epc;
> >  
> >  	dw_pcie_edma_remove(pci);
> 
> Hello Mani,
> 
> In this message:
> https://lore.kernel.org/linux-pci/20240130062938.GB32821@thinkpad/
> 
> You mentioned that you were going to clean up the BARs.

Yes, I did and it is still in my queue.

> (Like I wrote in that thread, I really think that we should merge a fix for
> the broken "do we have a saved value from find_first_zero_bit() in the array",
> by using a "if (!saved_value[bar])", when find_first_zero_bit() returns zero.)
> 

Hmm, yeah that logic is flawed. Let me take another look.

> However, regardless of that, I do not see that this series (neither
> dw_pcie_ep_cleanup(), nor dw_pcie_ep_linkdown()), calls any function which
> will clean up the BARs.
> 
> Since e.g. qcom-ep.c does a reset_control_assert() during perst
> assert/deassert, which should clear sticky registers, I think that
> you should let dw_pcie_ep_cleanup() clean up the BARs using
> dw_pcie_ep_clear_bar().
> 

As I mentioned earlier, it is the job of the EPF drivers to clear the BARs since
they allocate them. I'm trying to reduce the implicit resetting wherever we
could.

The proper fix is to add the LINK_DOWN callback to EPF drivers and do cleanup.
I'm planning to submit a series for that after this one.

- Mani

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