Re: [net-next PATCH] octeontx2: Add PTP clock driver for Octeon PTM clock.

Sai Krishna Gajula
2024-01-30T10:57:11Z

> -----Original Message-----
> From: Simon Horman <horms@kernel.org>
> Sent: Monday, January 29, 2024 4:29 PM
> To: Sai Krishna Gajula <saikrishnag@marvell.com>
> Cc: richardcochran@gmail.com; davem@davemloft.net; kuba@kernel.org;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil Kovvuri
> Goutham <sgoutham@marvell.com>; Geethasowjanya Akula
> <gakula@marvell.com>; Linu Cherian <lcherian@marvell.com>; Hariprasad
> Kelam <hkelam@marvell.com>; Subbaraya Sundeep Bhatta
> <sbhatta@marvell.com>; Naveen Mamindlapalli <naveenm@marvell.com>
> Subject: Re: [net-next PATCH] octeontx2: Add PTP clock driver for
> Octeon PTM clock.
>
> On Wed, Jan 24, 2024 at 12:11:56PM +0530, Sai Krishna wrote:
> > The PCIe PTM(Precision time measurement) protocol provides precise
> > coordination of events across multiple components like PCIe host
> > clock, PCIe EP PHC local clocks of PCIe devices. This patch adds
> > support for ptp clock based PTM clock. We can use this PTP device to
> > sync the PTM time with CLOCK_REALTIME or other PTP PHC devices using
> > phc2sys.
> >
> > Signed-off-by: Sai Krishna <saikrishnag@marvell.com>
> > Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
> > Signed-off-by: Sunil Kovvuri Goutham <sgoutham@marvell.com>
>
> Hi Sai,
>
> some minor review items from my side.
>
> > diff --git a/drivers/ptp/ptp_octeon_ptm.c
> > b/drivers/ptp/ptp_octeon_ptm.c
>
> ...
>
> > +static u32 read_pcie_config32(int ep_pem, int cfg_addr) {
> > + void __iomem *addr;
> > + u64 val;
> > +
> > + if (oct_ptp_clock.cn10k_variant) {
> > + addr = ioremap(PEMX_PFX_CSX_PFCFGX(ep_pem, 0,
> cfg_addr), 8);
> > + if (!addr) {
> > + pr_err("PTM_EP: Failed to ioremap Octeon CSR
> space\n");
> > + return -1U;
> > + }
> > + val = readl(addr);
> > + iounmap(addr);
> > + } else {
> > + addr = ioremap(PEMX_CFG_RD(ep_pem), 8);
> > + if (!addr) {
> > + pr_err("PTM_EP: Failed to ioremap Octeon CSR
> space\n");
> > + return -1U;
> > + }
> > + val = ((1 << 15) | (cfg_addr & 0xfff));
> > + writeq(val, addr);
>
> This causes a build failure on x86_32 because writeq() is undefined.

Ack, Will add ARM64 dependency in Kconfig (depends on (64BIT && COMPILE_TEST) || ARM64). Hope this works!!

>
> > + val = readq(addr) >> 32;
> > + iounmap(addr);
> > + }
> > + return (val & 0xffffffff);
> > +}
> > +
> > +static uint64_t octeon_csr_read(u64 csr_addr) {
> > + u64 val;
> > + void __iomem *addr;
>
> nit: In Networking code, please consider arranging local variables
> in reverse xmas tree order - longest line to shortest.

Ack, yeah missed this.. will change in patch V2.

>
> > +
> > + addr = ioremap(csr_addr, 8);
> > + if (!addr) {
> > + pr_err("PTM_EP: Failed to ioremap CSR space\n");
> > + return -1UL;
> > + }
> > + val = (u64)READ_ONCE(*(u64 __iomem *)addr);
>
> Sparse seems unhappy about this cast.
> So if this is really what you want to do then probably a __force is needed in
> the cast.
>
> But I do wonder if there is an endian consideration that needs to be taken
> care of here. And, moreover, if a standard routine, such as ioread64(), could
> be used instead of this function.
>
> N.B. as per the note on writeq, possibly this only works on 64bit systems.
>
> Likewise elsewhere in this patch.
>

Ack, will submit the changes in patch V2.

> > + iounmap(addr);
> > + return val;
> > +}
>
> ...
>
> > +static int __init ptp_oct_ptm_init(void) {
> > + struct pci_dev *pdev = NULL;
> > +
> > + pdev = pci_get_device(PCI_VENDOR_ID_CAVIUM,
> > + PCI_DEVID_OCTEONTX2_PTP, pdev);
> > + if (!pdev)
> > + return 0;
> > +
> > + if (octeon_csr_read(PEMX_CFG) & 0x1ULL) {
> > + pr_err("PEM0 is configured as RC\n");
> > + return 0;
> > + }
> > +
> > + if (is_otx2_support_ptm(pdev)) {
> > + oct_ptp_clock.cn10k_variant = 0;
> > + } else if (is_cn10k_support_ptm(pdev)) {
> > + oct_ptp_clock.cn10k_variant = 1;
> > + } else {
> > + /* PTM_EP: unsupported processor */
> > + return 0;
> > + }
> > +
> > + ptm_ctl_addr = ioremap(PEMX_PTM_CTL, 8);
> > + if (!ptm_ctl_addr) {
> > + pr_err("PTM_EP: Failed to ioremap CSR space\n");
> > + return 0;
> > + }
> > +
> > + ptm_lcl_addr = ioremap(PEMX_PTM_LCL_TIME, 8);
> > + if (!ptm_lcl_addr) {
> > + pr_err("PTM_EP: Failed to ioremap CSR space\n");
> > + return 0;
> > + }
> > +
> > + oct_ptp_clock.caps = ptp_oct_caps;
> > +
> > + oct_ptp_clock.ptp_clock = ptp_clock_register(&oct_ptp_clock.caps,
> > +NULL);
> > +
> > + pr_info("PTP device index for PTM clock:%d\n",
> > +oct_ptp_clock.ptp_clock->index);
>
> It seems that the pr_info() call above assumes that oct_ptp_clock.ptp_clock
> is not an error, but it may be.
>
> Perhaps something like this is more appropriate:
>
> oct_ptp_clock.ptp_clock = ...
> if (IS_ERR(oct_ptp_clock.ptp_clock))
> ERR_PTR(oct_ptp_clock.ptp_clock);
>
> pr_info(...)
> ...
>
> return 0;
>
> Flagged by Smatch.

Ack, will submit the changes in patch V2.

>
> > + pr_info("cn10k_variant %d\n", oct_ptp_clock.cn10k_variant);
> > +
> > + return PTR_ERR_OR_ZERO(oct_ptp_clock.ptp_clock);
> > +}
> > +
> > +module_init(ptp_oct_ptm_init);
> > +module_exit(ptp_oct_ptm_exit);
> > +
> > +MODULE_AUTHOR("Marvell Inc.");
> > +MODULE_DESCRIPTION("PTP PHC clock using PTM");
> MODULE_LICENSE("GPL");
> > --
> > 2.25.1

Thanks,
Sai