linux-kernel - Re: [RFC PATCH 12/14] cxl: Add basic debugging

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Date:   Tue, 8 Dec 2020 17:17:36 -0800
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ben Widawsky <ben.widawsky@...el.com>
Cc:     linux-cxl@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PCI <linux-pci@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        "Kelley, Sean V" <sean.v.kelley@...el.com>,
        Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Jon Masters <jcm@...masters.org>,
        Chris Browy <cbrowy@...ry-design.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [RFC PATCH 12/14] cxl: Add basic debugging

On Tue, Dec 8, 2020 at 4:24 PM Ben Widawsky <ben.widawsky@...el.com> wrote:
>
> Provide a standard debug function for use throughout the driver.
>
> Signed-off-by: Ben Widawsky <ben.widawsky@...el.com>
> ---
>  drivers/cxl/cxl.h |  3 +++
>  drivers/cxl/mem.c | 26 +++++++++++++++++++++++++-
>  2 files changed, 28 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index 77c2dee6843c..e5afb89dab0b 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -9,6 +9,9 @@
>  #include <linux/bitops.h>
>  #include <linux/io.h>
>
> +#define cxl_debug(fmt, ...)                                                    \
> +       pr_debug("CXL DEBUG: %s: " fmt, __func__, ##__VA_ARGS__)
> +

This should be dev_dbg(), then you don't need the CXL DEBUG prefix. In
fact you don't need a cxl_debug() macro at all in that case. cxl_mem
might need a ->dev attribute for this purpose.

>  #define CXL_SET_FIELD(value, field)                                            \
>         ({                                                                     \
>                 WARN_ON(!FIELD_FIT(field##_MASK, value));                      \
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index a2cea7ac7cc6..6b2f8d3776b5 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -122,9 +122,12 @@ static int cxl_mem_wait_for_doorbell(struct cxl_mem *cxlm)
>  {
>         const int timeout = msecs_to_jiffies(2000);
>         const unsigned long start = jiffies;
> +       unsigned long end = start;
>
>         while (cxl_doorbell_busy(cxlm)) {
> -               if (time_after(jiffies, start + timeout)) {
> +               end = jiffies;
> +
> +               if (time_after(end, start + timeout)) {
>                         /* Check again in case preempted before timeout test */
>                         if (!cxl_doorbell_busy(cxlm))
>                                 break;
> @@ -133,6 +136,8 @@ static int cxl_mem_wait_for_doorbell(struct cxl_mem *cxlm)
>                 cpu_relax();
>         }
>
> +       cxl_debug("Doorbell wait took %dms",
> +                 jiffies_to_msecs(end) - jiffies_to_msecs(start));
>         return 0;
>  }
>
> @@ -180,6 +185,8 @@ static int cxl_mem_mbox_send_cmd(struct cxl_mem *cxlm,
>         }
>
>         /* #4 */
> +       cxl_debug("Sending command to %s\n",
> +                 dev_driver_string(&cxlm->pdev->dev));

dev_dbg() already includes dev_driver_string().

>         cxl_write_mbox_reg32(cxlm, CXLDEV_MB_CTRL_OFFSET,
>                              CXLDEV_MB_CTRL_DOORBELL);
>
> @@ -308,6 +315,8 @@ static int cxl_mem_open(struct inode *inode, struct file *file)
>         if (!cxlmd)
>                 return -ENXIO;
>
> +       cxl_debug("Opened %pD\n", file);
> +
>         file->private_data = cxlmd;
>
>         return 0;
> @@ -383,6 +392,10 @@ static int handle_mailbox_cmd_from_user(struct cxl_memdev *cxlmd,
>                 .size_in = cmd->info.size_in,
>                 .size_out = size_out,
>         };
> +       cxl_debug("Submitting command for user\n"
> +                 "\topcode: %x\n"
> +                 "\tsize: %zub/%zub\n",
> +                 mbox_cmd.opcode, mbox_cmd.size_in, mbox_cmd.size_out);
>         rc = cxl_mem_mbox_send_cmd(cxlmd->cxlm, &mbox_cmd);
>         cxl_mem_mbox_put(cxlmd->cxlm);
>         if (rc)
> @@ -479,6 +492,8 @@ static long cxl_mem_ioctl(struct file *file, unsigned int cmd, unsigned long arg
>                 u32 n_commands;
>                 int i, j;
>
> +               cxl_debug("Query IOCTL\n");
> +
>                 if (get_user(n_commands, (u32 __user *)arg))
>                         return -EFAULT;
>
> @@ -511,6 +526,8 @@ static long cxl_mem_ioctl(struct file *file, unsigned int cmd, unsigned long arg
>                 struct cxl_mem_command c;
>                 int rc;
>
> +               cxl_debug("Send IOCTL\n");
> +
>                 rc = cxl_validate_cmd_from_user(u, &c);
>                 if (rc)
>                         return rc;
> @@ -843,6 +860,13 @@ static int cxl_mem_identify(struct cxl_mem *cxlm)
>
>         id = (struct cxl_mbox_identify *)mbox_cmd.payload;
>
> +       cxl_debug("Driver identify command\n"
> +                 "\tFirmware Version: %s\n"
> +                 "\tTotal Capacity: %llu (%llu persistent)\n"
> +                 "\tLSA size: %u\n",
> +                 id->fw_revision, id->total_capacity, id->persistent_capacity,
> +                 id->lsa_size);
> +

Seems not necessary for details that are published in sysfs?