linux-kernel - Re: [PATCH v7 10/12] PCI: qcom: Add SM8550 PCIe support

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Message-ID: <Y+PYeRo8X8ugXyoi@hovoldconsulting.com>
Date:   Wed, 8 Feb 2023 18:14:33 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Abel Vesa <abel.vesa@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        "vkoul@...nel.org" <vkoul@...nel.org>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 10/12] PCI: qcom: Add SM8550 PCIe support

On Wed, Feb 08, 2023 at 07:11:08PM +0200, Abel Vesa wrote:
> On 23-02-08 19:10:17, Abel Vesa wrote:
> > On 23-02-08 17:40:03, Johan Hovold wrote:
> > > On Mon, Feb 06, 2023 at 05:11:01PM +0200, Abel Vesa wrote:
> > > > On 23-02-03 10:49:24, Johan Hovold wrote:
> > > > > On Fri, Feb 03, 2023 at 10:18:05AM +0200, Abel Vesa wrote:
> > > > > > Add compatible for both PCIe found on SM8550.
> > > > > > Also add the cnoc_pcie_sf_axi clock needed by the SM8550.
> > > > > 
> > > > > nit: You're now also adding 'noc_aggr'
> > > > > 
> > > > > > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > > > > > Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>
> > > > > > Reviewed-by: Manivannan Sadhasivam <mani@...nel.org>
> > > > > > ---
> > > 
> > > > > > @@ -182,10 +182,10 @@ struct qcom_pcie_resources_2_3_3 {
> > > > > >  
> > > > > >  /* 6 clocks typically, 7 for sm8250 */
> > > > > >  struct qcom_pcie_resources_2_7_0 {
> > > > > > -	struct clk_bulk_data clks[12];
> > > > > > +	struct clk_bulk_data clks[14];
> > > > > >  	int num_clks;
> > > > > >  	struct regulator_bulk_data supplies[2];
> > > > > > -	struct reset_control *pci_reset;
> > > > > > +	struct reset_control *rst;
> > > > > 
> > > > > Please name this one 'reset' or 'resets' (e.g. to avoid hard to parse
> > > > > things like res->rst below).
> > > > 
> > > > Well, it would then be inconsitent with 2_3_3 and 2_9_0, which both use
> > > > rst.
> > > 
> > > Yeah, I saw that. Fortunately these resources are completely
> > > independent, but whatever.
> > 
> > Will do it in the next version then.

Or just leave it as is.

> > > > > >  };
> > > > > >  
> > > > > >  struct qcom_pcie_resources_2_9_0 {
> > > > > > @@ -1177,9 +1177,9 @@ static int qcom_pcie_get_resources_2_7_0(struct qcom_pcie *pcie)
> > > > > >  	unsigned int idx;
> > > > > >  	int ret;
> > > > > >  
> > > > > > -	res->pci_reset = devm_reset_control_get_exclusive(dev, "pci");
> > > > > > -	if (IS_ERR(res->pci_reset))
> > > > > > -		return PTR_ERR(res->pci_reset);
> > > > > > +	res->rst = devm_reset_control_array_get_exclusive(dev);
> > > > > > +	if (IS_ERR(res->rst))
> > > > > > +		return PTR_ERR(res->rst);
> > > > > 
> > > > > So the reset array implementation apparently both asserts and deasserts
> > > > > the resets in the order specified in DT (i.e. does not deassert in
> > > > > reverse order).
> > > > > 
> > > > > Is that ok also for the new "pci" and "link_down" resets?
> > > > 
> > > > According to the HPG, yes, this is perfectly fine. It specifically says
> > > > to assert the pcie reset and then continues saying to assert the
> > > > link_down reset.
> > > 
> > > Ok, but that doesn't really say anything about whether it's ok to
> > > *deassert* them in the same order, which was what I asked about.
> > 
> > Actually, what I wanted to say is that the HPG says something like this:
> > 
> > "assert pcie reset, then assert link_down"
> > 
> > and then at the end it literaly repeats the same phrase.
> 
> but uses deassert instead of assert ...

Ok, then it seems to match the implementation. Thanks for clarifying.

Johan