linux-kernel - Re: [PATCH v5 0/2] phy: qcom: qmp-pcie: Add PCIe PHY no

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Message-ID: <20250314145407.5uuw7ucrdhca4z5i@thinkpad>
Date: Fri, 14 Mar 2025 20:24:07 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Vinod Koul <vkoul@...nel.org>
Cc: "Wenbin Yao (Consultant)" <quic_wenbyao@...cinc.com>, kishon@...nel.org,
	p.zabel@...gutronix.de, dmitry.baryshkov@...aro.org,
	abel.vesa@...aro.org, quic_qianyu@...cinc.com,
	neil.armstrong@...aro.org, quic_devipriy@...cinc.com,
	konrad.dybcio@....qualcomm.com, linux-arm-msm@...r.kernel.org,
	linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/2] phy: qcom: qmp-pcie: Add PCIe PHY no_csr reset
 support

On Tue, Mar 11, 2025 at 01:29:15AM +0530, Vinod Koul wrote:
> On 10-03-25, 16:58, Wenbin Yao (Consultant) wrote:
> > On 2/26/2025 6:35 PM, Wenbin Yao wrote:
> > > The series aims to skip phy register programming and drive PCIe PHY with
> > > register setting programmed in bootloader by simply toggling no_csr reset,
> > > which once togglled, PHY hardware will be reset while PHY registers are
> > > retained.
> > > 
> > > First, determine whether PHY setting can be skipped by checking
> > > QPHY_START_CTRL register and the existence of nocsr reset. If it is
> > > programmed and no_csr reset is supported, do no_csr reset and skip BCR
> > > reset which will reset entire PHY.
> > > 
> > > This series also remove has_nocsr_reset flag in qmp_phy_cfg structure and
> > > decide whether the PHY supports nocsr reset by checking the existence of
> > > nocsr reset in device tree.
> > > 
> > > The series are tested on X1E80100-QCP and HDK8550.
> > > 
> > > The commit messages of this patchset have been modified based on comments
> > > and suggestions.
> > > 
> > > Changes in v5:
> > > - Add a check whether the init sequences are exist if the PHY needs to be
> > >    initialized to Patch 2/2.
> > > - Link to v4: https://lore.kernel.org/all/20250220102253.755116-1-quic_wenbyao@quicinc.com/
> > > 
> > > Changes in v4:
> > > - Add Philipp's Reviewed-by tag to Patch 1/2.
> > > - Use PHY instead of phy in comments in Patch 2/2.
> > > - Use "if (qmp->nocsr_reset)" instead of "if (!qmp->nocsr_reset)" in
> > >    function qmp_pcie_exit for readability in Patch 2/2.
> > > - Use goto statements in function qmp_pcie_power_on and qmp_pcie_power_off
> > >    for readability in Patch 2/2.
> > > - Refine the comment of why not checking qmp->skip_init when reset PHY in
> > >    function qmp_pcie_power_off in Patch 2/2.
> > > - Link to v3: https://lore.kernel.org/all/20250214104539.281846-1-quic_wenbyao@quicinc.com/
> > > 
> > > Changes in v3:
> > > - Replace devm_reset_control_get_exclusive with
> > >    devm_reset_control_get_optional_exclusive when get phy_nocsr reset
> > >    control in Patch 1/2.
> > > - Do not ignore -EINVAL when get phy_nocsr reset control in Patch 1/2.
> > > - Replace phy_initialized with skip_init in struct qmp_pcie in Patch 2/2.
> > > - Add a comment to why not check qmp->skip_init in function
> > >    qmp_pcie_power_off in Patch 2/2.
> > > - Link to v2: https://lore.kernel.org/all/20250211094231.1813558-1-quic_wenbyao@quicinc.com/
> > > 
> > > Changes in v2:
> > > - Add Abel's and Manivannan's Reviewed-by tag to Patch 1/2.
> > > - Refine commit msg of Patch 2/2.
> > > - Link to v1: https://lore.kernel.org/all/20250121094140.4006801-1-quic_wenbyao@quicinc.com/
> > > 
> > > Konrad Dybcio (1):
> > >    phy: qcom: pcie: Determine has_nocsr_reset dynamically
> > > 
> > > Qiang Yu (1):
> > >    phy: qcom: qmp-pcie: Add PHY register retention support
> > > 
> > >   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 86 +++++++++++++++++-------
> > >   1 file changed, 63 insertions(+), 23 deletions(-)
> > > 
> > > 
> > > base-commit: bcf2acd8f64b0a5783deeeb5fd70c6163ec5acd7
> > 
> > Hi, do you have any futher comments?
> 
> Patches lgtm, It would be great if this was tested by someone as well...
> Abel, Stephan, Neil can you folks test this and provide T-B
> 

I tested the previous version and it worked well on X1P40100-CRD. Will give this
version a go and give my tag.

> I am also concerned about bootloader assumptions esp if the Qcom boot
> chain is skipped
> 

In that case, someone should add the PHY init sequence to the driver. That's why
I wanted to have the check in place to avoid silently failing PHY
initialization. Right now, the driver will error out if there is no init
sequence available.

- Mani

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