Re: [PATCH v2] usb: typec: intel_pmc_mux: Expose IOM port status to debugfs

[Rajat Khandelwal]

Hi,

On 4/17/2023 11:42 AM, Greg KH wrote:
> On Mon, Apr 17, 2023 at 11:28:18AM +0530, Rajat Khandelwal wrote:
> > Hi,
> >
> > On 4/15/2023 11:01 AM, Greg KH wrote:
> > > On Fri, Apr 14, 2023 at 01:49:10PM +0530, Rajat Khandelwal wrote:
> > > > IOM status has a crucial role during debugging to check the
> > > > current state of the type-C port.
> > > > There are ways to fetch the status, but all those require the
> > > > IOM port status offset, which could change with platform.
> > > >
> > > > Make a debugfs directory for intel_pmc_mux and expose the status
> > > > under it per port basis.
> > > >
> > > > Signed-off-by: Rajat Khandelwal <rajat.khandelwal@xxxxxxxxxxxxxxx>
> > > > ---
> > > >
> > > > v2:
> > > > 1. Remove static declaration of the debugfs root for 'intel_pmc_mux'
> > > > 2. Remove explicitly defined one-liner functions
> > > >
> > > >    drivers/usb/typec/mux/intel_pmc_mux.c | 34 +++++++++++++++++++++++++++
> > > >    1 file changed, 34 insertions(+)
> > > >
> > > > diff --git a/drivers/usb/typec/mux/intel_pmc_mux.c b/drivers/usb/typec/mux/intel_pmc_mux.c
> > > > index 34e4188a40ff..1d43b111781e 100644
> > > > --- a/drivers/usb/typec/mux/intel_pmc_mux.c
> > > > +++ b/drivers/usb/typec/mux/intel_pmc_mux.c
> > > > @@ -15,6 +15,7 @@
> > > >    #include <linux/usb/typec_mux.h>
> > > >    #include <linux/usb/typec_dp.h>
> > > >    #include <linux/usb/typec_tbt.h>
> > > > +#include <linux/debugfs.h>
> > > >    #include <asm/intel_scu_ipc.h>
> > > > @@ -639,9 +640,34 @@ static int pmc_usb_probe_iom(struct pmc_usb *pmc)
> > > >    	return 0;
> > > >    }
> > > > +static int port_iom_status_show(struct seq_file *s, void *unused)
> > > > +{
> > > > +	struct pmc_usb_port *port = s->private;
> > > > +
> > > > +	update_port_status(port);
> > > > +	seq_printf(s, "0x%08x\n", port->iom_status);
> > > > +
> > > > +	return 0;
> > > > +}
> > > > +DEFINE_SHOW_ATTRIBUTE(port_iom_status);
> > > > +
> > > > +static void pmc_mux_port_debugfs_init(struct pmc_usb_port *port,
> > > > +				      struct dentry *pmc_mux_debugfs_root)
> > > > +{
> > > > +	struct dentry *debugfs_dir;
> > > > +	char name[6];
> > > > +
> > > > +	snprintf(name, sizeof(name), "port%d", port->usb3_port - 1);
> > > > +
> > > > +	debugfs_dir = debugfs_create_dir(name, pmc_mux_debugfs_root);
> > > > +	debugfs_create_file("iom_status", 0400, debugfs_dir, port,
> > > > +			    &port_iom_status_fops);
> > > > +}
> > > > +
> > > >    static int pmc_usb_probe(struct platform_device *pdev)
> > > >    {
> > > >    	struct fwnode_handle *fwnode = NULL;
> > > > +	struct dentry *pmc_mux_debugfs_root;
> > > >    	struct pmc_usb *pmc;
> > > >    	int i = 0;
> > > >    	int ret;
> > > > @@ -674,6 +700,8 @@ static int pmc_usb_probe(struct platform_device *pdev)
> > > >    	if (ret)
> > > >    		return ret;
> > > > +	pmc_mux_debugfs_root = debugfs_create_dir("intel_pmc_mux", NULL);
> > > What happens when you have more than one device in the system at the
> > > same time?
> > I'm sorry I didn't understand the question. We would have separate directories
> > for all the ports which would contain the 'iom_status' file, thus representing
> > status for all the ports individually.
> > Can you rephrase the question since I guess you had something else in mind?
> Can you please show the output of the directory
> /sys/kernel/debug/intel_pmc_mux/ with multiple pmc devices in the system
> at the same time?

Sorry, I don't own a system with multiple PMCs. Anyways, do we even have
a system with such design?

Thanks
Rajat

> This code seems to want to create that directory for every platform
> device that matches this signature, so that implies you can not have
> more than one of them at a time, which is not good and an artificial
> restriction you are placing on the driver.
>
> thanks,
>
> greg k-h