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Message-ID: <20201209020433.bzsuqudbgtpbtggk@intel.com>
Date: Tue, 8 Dec 2020 18:04:33 -0800
From: Ben Widawsky <ben.widawsky@...el.com>
To: Dan Williams <dan.j.williams@...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 20-12-08 17:17:36, Dan Williams wrote:
> 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.
>
I really like the ability to turn specific messages on and off at will. (FWIW,
__func__ is also redundant because pr_debug allows you to specify a flag to
always print the function name). While it's not very frequent events here, in
the future it likely will be and I think it can be really helpful to be able to
have that level of control.
If you want to avoid creating a new debug functionality, I'm okay with that, but
I'd really like to use pr_debug instead of dev_dbg for those messages going
forward. Once you take that step, it seems giving contributors a macro named
'cxl_debug' so they don't have to figure out when to use what, makes sense. My
mental separation is, dev_* is useful primarily for errors and initialization
debug messaging, pr_debug/trace_printk is for runtime things.
I probably should have put that in the commit message...
> > #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?
I was thinking for cases where driver doesn't bind, seeing the identify
information could be useful. This is one case where dev_dbg would also serve
IMO.
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