linux-kernel - Re: [PATCH v3 6/7] phy: qcom-qmp-pcie: add support for ipq9574 gen3x2 PHY

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Message-ID: <CAA8EJppGW=qyk2P6Z_S=dp0njsCjqZaXjw8qU4MY1HOZR-N=4A@mail.gmail.com>
Date: Wed, 17 Apr 2024 00:50:49 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: "Alex G." <mr.nuke.me@...il.com>, Varadarajan Narayanan <quic_varada@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Michael Turquette <mturquette@...libre.com>, 
	Stephen Boyd <sboyd@...nel.org>, Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
	linux-arm-msm@...r.kernel.org, linux-pci@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-phy@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v3 6/7] phy: qcom-qmp-pcie: add support for ipq9574 gen3x2 PHY

On Wed, 17 Apr 2024 at 00:25, Alex G. <mr.nuke.me@...il.com> wrote:
>
> Hi Dmitry,
>
> On 4/15/24 16:25, mr.nuke.me@...il.com wrote:
> >
> >
> > On 4/15/24 15:10, Dmitry Baryshkov wrote:
> >> On Mon, 15 Apr 2024 at 21:23, Alexandru Gagniuc <mr.nuke.me@...il.com>
> >> wrote:
> >>>
> >>> Add support for the gen3x2 PCIe PHY on IPQ9574, ported form downstream
> >>> 5.4 kernel. Only the serdes and pcs_misc tables are new, the others
> >>> being reused from IPQ8074 and IPQ6018 PHYs.
> >>>
> >>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@...il.com>
> >>> ---
> >>>   drivers/phy/qualcomm/phy-qcom-qmp-pcie.c      | 136 +++++++++++++++++-
> >>>   .../phy/qualcomm/phy-qcom-qmp-pcs-pcie-v5.h   |  14 ++
> >>>   2 files changed, 149 insertions(+), 1 deletion(-)
> >>>
> >>
> >> [skipped]
> >>
> >>> @@ -2448,7 +2542,7 @@ static inline void qphy_clrbits(void __iomem
> >>> *base, u32 offset, u32 val)
> >>>
> >>>   /* list of clocks required by phy */
> >>>   static const char * const qmp_pciephy_clk_l[] = {
> >>> -       "aux", "cfg_ahb", "ref", "refgen", "rchng", "phy_aux",
> >>> +       "aux", "cfg_ahb", "ref", "refgen", "rchng", "phy_aux",
> >>> "anoc", "snoc"
> >>
> >> Are the NoC clocks really necessary to drive the PHY? I think they are
> >> usually connected to the controllers, not the PHYs.
> >
> > The system will hang if these clocks are not enabled. They are also
> > attached to the PHY in the QCA 5.4 downstream kernel.

Interesting.
I see that Varadarajan is converting these clocks into interconnects.
Maybe it's better to wait for those patches to land and use
interconnects instead. I think it would better suit the
infrastructure.

Varadarajan, could you please comment, are these interconnects
connected to the PHY too or just to the PCIe controller?

> >
> They are named "anoc_lane", and "snoc_lane" in the downstream kernel.
> Would you like me to use these names instead?

I'm fine either way.

> e>>>   };
> >>>
> >>>   /* list of regulators */
> >>> @@ -2499,6 +2593,16 @@ static const struct qmp_pcie_offsets
> >>> qmp_pcie_offsets_v4x1 = {
> >>>          .rx             = 0x0400,
> >>>   };
> >>>
> >>> +static const struct qmp_pcie_offsets qmp_pcie_offsets_ipq9574 = {
> >>> +       .serdes         = 0,
> >>> +       .pcs            = 0x1000,
> >>> +       .pcs_misc       = 0x1400,
> >>> +       .tx             = 0x0200,
> >>> +       .rx             = 0x0400,
> >>> +       .tx2            = 0x0600,
> >>> +       .rx2            = 0x0800,
> >>> +};
> >>> +
> >>>   static const struct qmp_pcie_offsets qmp_pcie_offsets_v4x2 = {
> >>>          .serdes         = 0,
> >>>          .pcs            = 0x0a00,
> >>> @@ -2728,6 +2832,33 @@ static const struct qmp_phy_cfg
> >>> sm8250_qmp_gen3x1_pciephy_cfg = {
> >>>          .phy_status             = PHYSTATUS,
> >>>   };
> >>>
> >>> +static const struct qmp_phy_cfg ipq9574_pciephy_gen3x2_cfg = {
> >>> +       .lanes                  = 2,
> >>> +
> >>> +       .offsets                = &qmp_pcie_offsets_ipq9574,
> >>> +
> >>> +       .tbls = {
> >>> +               .serdes         = ipq9574_gen3x2_pcie_serdes_tbl,
> >>> +               .serdes_num     =
> >>> ARRAY_SIZE(ipq9574_gen3x2_pcie_serdes_tbl),
> >>> +               .tx             = ipq8074_pcie_gen3_tx_tbl,
> >>> +               .tx_num         = ARRAY_SIZE(ipq8074_pcie_gen3_tx_tbl),
> >>> +               .rx             = ipq6018_pcie_rx_tbl,
> >>> +               .rx_num         = ARRAY_SIZE(ipq6018_pcie_rx_tbl),
> >>> +               .pcs            = ipq6018_pcie_pcs_tbl,
> >>> +               .pcs_num        = ARRAY_SIZE(ipq6018_pcie_pcs_tbl),
> >>> +               .pcs_misc       = ipq9574_gen3x2_pcie_pcs_misc_tbl,
> >>> +               .pcs_misc_num   =
> >>> ARRAY_SIZE(ipq9574_gen3x2_pcie_pcs_misc_tbl),
> >>> +       },
> >>> +       .reset_list             = ipq8074_pciephy_reset_l,
> >>> +       .num_resets             = ARRAY_SIZE(ipq8074_pciephy_reset_l),
> >>> +       .vreg_list              = NULL,
> >>> +       .num_vregs              = 0,
> >>> +       .regs                   = pciephy_v4_regs_layout,
> >>
> >> So, is it v4 or v5?
> >
> > Please give me a day or so to go over my notes and give you a more
> > coherent explanation of why this versioning was chosen. I am only
> > working from the QCA 5.4 downstream sources. I don't have any
> > documentation for the silicon
>
> The downstream QCA kernel uses the same table for ipq6018, ipq8074-gen3,
> and ipq9574. It is named "ipq_pciephy_gen3_regs_layout". Thus, it made
> sense to use the same upstream table for ipq9574, "pciephy_v4_regs_layout".
>
> As far as the register tables go, the pcs/pcs_misc are squashed into the
> same table in the downstream 5.4 kernel. I was able to separate the two
> tables because the pcs_misc registers were defined with an offset of
> 0x400. For example:
>
> /* QMP V2 PHY for PCIE gen3 2 Lane ports - PCS Misc registers */
> #define PCS_PCIE_X2_POWER_STATE_CONFIG2                    0x40c
> #define PCS_PCIE_X2_POWER_STATE_CONFIG4                    0x414
> #define PCS_PCIE_X2_ENDPOINT_REFCLK_DRIVE                  0x420
> #define PCS_PCIE_X2_L1P1_WAKEUP_DLY_TIME_AUXCLK_L          0x444
> #define PCS_PCIE_X2_L1P1_WAKEUP_DLY_TIME_AUXCLK_H          0x448
> #define PCS_PCIE_X2_L1P2_WAKEUP_DLY_TIME_AUXCLK_L          0x44c
> #define PCS_PCIE_X2_L1P2_WAKEUP_DLY_TIME_AUXCLK_H          0x450
> ...
>
> Here, QPHY_V4_PCS_PCIE_POWER_STATE_CONFIG2 = 0xc would be correct,
> assuming a pcs_misc offset of 0x400. However, starting with
> ENDPOINT_REFCLK_DRIVE, the register would be
> QPHY_V4_PCS_PCIE_ENDPOINT_REFCLK_DRIVE = 0x1c. Our offsets are off-by 0x4.
>
> The existing V5 offsets, on the other hand, were all correct. For this
> reason, I considered that V5 is the most likely place to add the missing
> PCS misc definitions.

Ok, sounds sane. Please use _v5 for the regs layout.

>
> Is this explanation sufficiently convincing? Where does the v4/v5 scheme
> in upstream kernel originate?

Sometimes it's vendor kernels, sometimes it's a feedback from devs
that have access to actual specs.


--
With best wishes
Dmitry