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

[Alex G.]

Hi Dmitry,

On 4/15/24 16:25, mr.nuke.me@xxxxxxxxx wrote:
> On 4/15/24 15:10, Dmitry Baryshkov wrote:
> > On Mon, 15 Apr 2024 at 21:23, Alexandru Gagniuc <mr.nuke.me@xxxxxxxxx> 
> > 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@xxxxxxxxx>
> > > ---
> > >   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.
They are named "anoc_lane", and "snoc_lane" in the downstream kernel. 
Would you like me to use these names instead?

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.

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

Alex