linux-kernel - Re: [PATCH v6 1/3] PCI: qcom: Add equalization settings for 8.0 GT/s and 32.0 GT/s

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Message-ID: <20250904161448.GA1265317@bhelgaas>
Date: Thu, 4 Sep 2025 11:14:48 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Ziyue Zhang <ziyue.zhang@....qualcomm.com>
Cc: andersson@...nel.org, konradybcio@...nel.org, robh@...nel.org,
	krzk+dt@...nel.org, conor+dt@...nel.org, jingoohan1@...il.com,
	mani@...nel.org, lpieralisi@...nel.org, kwilczynski@...nel.org,
	bhelgaas@...gle.com, johan+linaro@...nel.org, vkoul@...nel.org,
	kishon@...nel.org, neil.armstrong@...aro.org, abel.vesa@...aro.org,
	kw@...ux.com, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-phy@...ts.infradead.org,
	qiang.yu@....qualcomm.com, quic_krichai@...cinc.com,
	quic_vbadigan@...cinc.com
Subject: Re: [PATCH v6 1/3] PCI: qcom: Add equalization settings for 8.0 GT/s
 and 32.0 GT/s

On Thu, Sep 04, 2025 at 02:52:23PM +0800, Ziyue Zhang wrote:
> Add lane equalization setting for 8.0 GT/s and 32.0 GT/s to enhance link
> stability and avoid AER Correctable Errors reported on some platforms
> (eg. SA8775P).
>
> 8.0 GT/s, 16.0 GT/s and 32.0 GT/s require the same equalization setting.
> This setting is programmed into a group of shadow registers, which can be
> switched to configure equalization for different speeds by writing 00b,
> 01b and 10b to `RATE_SHADOW_SEL`.
> 
> Hence program equalization registers in a loop using link speed as index,
> so that equalization setting can be programmed for 8.0 GT/s, 16.0 GT/s
> and 32.0 GT/s.
> 
> Fixes: 489f14be0e0a ("arm64: dts: qcom: sa8775p: Add pcie0 and pcie1 nodes")
> 

Drop this blank line.

> Co-developed-by: Qiang Yu <qiang.yu@....qualcomm.com>
> Signed-off-by: Qiang Yu <qiang.yu@....qualcomm.com>
> Signed-off-by: Ziyue Zhang <ziyue.zhang@....qualcomm.com>

> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.c

> +	for (speed = PCIE_SPEED_8_0GT; speed <= pcie_link_speed[pci->max_link_speed]; ++speed) {

Use "speed++" when there's no need for preincrement to follow typical
drivers/pci/ usage.

No need to repost for these.