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SubjectRe: [PATCH] drm/komeda: Adds error event print functionality
On Mon, Jul 22, 2019 at 11:15:12AM +0000, james qian wang (Arm Technology China) wrote:
> On Fri, Jul 19, 2019 at 11:40:11AM +0000, Liviu Dudau wrote:
> > On Fri, Jul 19, 2019 at 09:09:30AM +0000, Lowry Li (Arm Technology China) wrote:
> > > Hi Liviu,
> > >
> > > On Thu, Jul 18, 2019 at 01:17:37PM +0000, Liviu Dudau wrote:
> > > > On Thu, Jun 27, 2019 at 04:10:36AM +0100, Lowry Li (Arm Technology China) wrote:
> > > > > Adds to print the event message when error happens and the same event
> > > > > will not be printed until next vsync.
> > > > >
> > > > > Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@arm.com>
> > > > > ---
> > > > > drivers/gpu/drm/arm/display/komeda/Makefile | 1 +
> > > > > drivers/gpu/drm/arm/display/komeda/komeda_dev.h | 13 ++
> > > > > drivers/gpu/drm/arm/display/komeda/komeda_event.c | 144 ++++++++++++++++++++++
> > > > > drivers/gpu/drm/arm/display/komeda/komeda_kms.c | 2 +
> > > > > 4 files changed, 160 insertions(+)
> > > > > create mode 100644 drivers/gpu/drm/arm/display/komeda/komeda_event.c
> > > > >
> > > > > diff --git a/drivers/gpu/drm/arm/display/komeda/Makefile b/drivers/gpu/drm/arm/display/komeda/Makefile
> > > > > index 38aa584..3f53d2d 100644
> > > > > --- a/drivers/gpu/drm/arm/display/komeda/Makefile
> > > > > +++ b/drivers/gpu/drm/arm/display/komeda/Makefile
> > > > > @@ -7,6 +7,7 @@ ccflags-y := \
> > > > > komeda-y := \
> > > > > komeda_drv.o \
> > > > > komeda_dev.o \
> > > > > + komeda_event.o \
> > > > > komeda_format_caps.o \
> > > > > komeda_coeffs.o \
> > > > > komeda_color_mgmt.o \
> > > > > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.h b/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> > > > > index 096f9f7..e863ec3 100644
> > > > > --- a/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> > > > > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> > > > > @@ -40,6 +40,17 @@
> > > > > #define KOMEDA_ERR_TTNG BIT_ULL(30)
> > > > > #define KOMEDA_ERR_TTF BIT_ULL(31)
> > > > >
> > > > > +#define KOMEDA_ERR_EVENTS \
> > > > > + (KOMEDA_EVENT_URUN | KOMEDA_EVENT_IBSY | KOMEDA_EVENT_OVR |\
> > > > > + KOMEDA_ERR_TETO | KOMEDA_ERR_TEMR | KOMEDA_ERR_TITR |\
> > > > > + KOMEDA_ERR_CPE | KOMEDA_ERR_CFGE | KOMEDA_ERR_AXIE |\
> > > > > + KOMEDA_ERR_ACE0 | KOMEDA_ERR_ACE1 | KOMEDA_ERR_ACE2 |\
> > > > > + KOMEDA_ERR_ACE3 | KOMEDA_ERR_DRIFTTO | KOMEDA_ERR_FRAMETO |\
> > > > > + KOMEDA_ERR_ZME | KOMEDA_ERR_MERR | KOMEDA_ERR_TCF |\
> > > > > + KOMEDA_ERR_TTNG | KOMEDA_ERR_TTF)
> > > > > +
> > > > > +#define KOMEDA_WARN_EVENTS KOMEDA_ERR_CSCE
> > > > > +
> > > > > /* malidp device id */
> > > > > enum {
> > > > > MALI_D71 = 0,
> > > > > @@ -207,6 +218,8 @@ struct komeda_dev {
> > > > >
> > > > > struct komeda_dev *dev_to_mdev(struct device *dev);
> > > > >
> > > > > +void komeda_print_events(struct komeda_events *evts);
> > > > > +
> > > > > int komeda_dev_resume(struct komeda_dev *mdev);
> > > > > int komeda_dev_suspend(struct komeda_dev *mdev);
> > > > > #endif /*_KOMEDA_DEV_H_*/
> > > > > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_event.c b/drivers/gpu/drm/arm/display/komeda/komeda_event.c
> > > > > new file mode 100644
> > > > > index 0000000..309dbe2
> > > > > --- /dev/null
> > > > > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_event.c
> > > > > @@ -0,0 +1,144 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0
> > > > > +/*
> > > > > + * (C) COPYRIGHT 2019 ARM Limited. All rights reserved.
> > > > > + * Author: James.Qian.Wang <james.qian.wang@arm.com>
> > > > > + *
> > > > > + */
> > > > > +#include <drm/drm_print.h>
> > > > > +
> > > > > +#include "komeda_dev.h"
> > > > > +
> > > > > +struct komeda_str {
> > > > > + char *str;
> > > > > + u32 sz;
> > > > > + u32 len;
> > > > > +};
> > > > > +
> > > > > +/* return 0 on success, < 0 on no space.
> > > > > + */
> > > > > +static int komeda_sprintf(struct komeda_str *str, const char *fmt, ...)
> > > > > +{
> > > > > + va_list args;
> > > > > + int num, free_sz;
> > > > > + int err;
> > > > > +
> > > > > + free_sz = str->sz - str->len;
> > > > > + if (free_sz <= 0)
> > > > > + return -ENOSPC;
> > > > > +
> > > > > + va_start(args, fmt);
> > > > > +
> > > > > + num = vsnprintf(str->str + str->len, free_sz, fmt, args);
> > > > > +
> > > > > + va_end(args);
> > > > > +
> > > > > + if (num <= free_sz) {
> > > > > + str->len += num;
> > > > > + err = 0;
> > > > > + } else {
> > > > > + str->len = str->sz;
> > > > > + err = -ENOSPC;
> > > > > + }
> > > > > +
> > > > > + return err;
> > > > > +}
> > > > > +
> > > > > +static void evt_sprintf(struct komeda_str *str, u64 evt, const char *msg)
> > > > > +{
> > > > > + if (evt)
> > > > > + komeda_sprintf(str, msg);
> > > > > +}
> > > > Why do we need this wrapper?
> > > The komeda_sprintf is a generic function and will be used by other
> > > places, while evt_sprintf is working for the detail event msg.
> >
> > Yeah, I'm not buying this argument any more. We should not create new functions
> > just because we want to save typing one if () condition. evt_sprintf does
> > nothing with the extra evt argument other than checking that it is not zero.
>
> Hi Liviu
>
> But I think we'd better to have this function which can remove
> many duplicate if () checks, and makes the code elegant and easy to
> read. and I think that why the concept of function has been
> introduced.
>
> And in linux we can see lot of functions or MACRO that just for save one
> word like:
>
> static inline void *kzalloc(size_t size, gfp_t flags)
> {
> return kmalloc(size, flags | __GFP_ZERO);
> }

This is a different (and valid use) of creating macros. kzalloc() does
something specific (initialises allocated memory with zeros) by using the
generic kmalloc() function. The added __GFP_ZERO has a specific outcome to the
invocation of the wrapped function. evt_sprintf() does nothing of this sort and
it is arguably wrong, as it drops any possibility of passing arguments to the
format string that komeda_sprintf() allows.


>
> And for this "if () check" specific, I think this is also very popular
> in linux like:
>
> static inline void __rcu_read_lock(void)
> {
> if (IS_ENABLED(CONFIG_PREEMPT_COUNT))
> preempt_disable();
> }
>
> static inline void __rcu_read_unlock(void)
> {
> if (IS_ENABLED(CONFIG_PREEMPT_COUNT))
> preempt_enable();
> }

These are inline functions wrapping around the fact that a config option might
be disabled. Not really the same thing with what we are talking here.

>
> thanks
> James
>
> > >
> > > > > +
> > > > > +static void evt_str(struct komeda_str *str, u64 events)
> > > > > +{
> > > > > + if (events == 0ULL) {
> > > > > + evt_sprintf(str, 1, "None");
> > > > > + return;
> > > > > + }
> > > > > +
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_VSYNC, "VSYNC|");
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_FLIP, "FLIP|");
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_EOW, "EOW|");
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_MODE, "OP-MODE|");
> > > > > +
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_URUN, "UNDERRUN|");
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_OVR, "OVERRUN|");
> > > > > +
> > > > > + /* GLB error */
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_MERR, "MERR|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_FRAMETO, "FRAMETO|");
> > > > > +
> > > > > + /* DOU error */
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_DRIFTTO, "DRIFTTO|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_FRAMETO, "FRAMETO|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TETO, "TETO|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_CSCE, "CSCE|");
> > > > > +
> > > > > + /* LPU errors or events */
> > > > > + evt_sprintf(str, events & KOMEDA_EVENT_IBSY, "IBSY|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_AXIE, "AXIE|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_ACE0, "ACE0|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_ACE1, "ACE1|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_ACE2, "ACE2|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_ACE3, "ACE3|");
> > > > > +
> > > > > + /* LPU TBU errors*/
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TCF, "TCF|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TTNG, "TTNG|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TITR, "TITR|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TEMR, "TEMR|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TTF, "TTF|");
> > > > > +
> > > > > + /* CU errors*/
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_CPE, "COPROC|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_ZME, "ZME|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_CFGE, "CFGE|");
> > > > > + evt_sprintf(str, events & KOMEDA_ERR_TEMR, "TEMR|");
> > > > > +
> > > > > + if (str->len > 0 && (str->str[str->len - 1] == '|')) {
> > > > > + str->str[str->len - 1] = 0;
> > > > > + str->len--;
> > > > > + }
> > > > > +}
> > > > > +
> > > > > +static bool is_new_frame(struct komeda_events *a)
> > > > > +{
> > > > > + return (a->pipes[0] | a->pipes[1]) & KOMEDA_EVENT_FLIP;
> > > > > +}
> > > > > +
> > > > > +void komeda_print_events(struct komeda_events *evts)
> > > > > +{
> > > > > + u64 print_evts = KOMEDA_ERR_EVENTS;
> > > > > + static bool en_print = true;
> > > > > +
> > > > > + /* reduce the same msg print, only print the first evt for one frame */
> > > > > + if (evts->global || is_new_frame(evts))
> > > > > + en_print = true;
> > > > > + if (!en_print)
> > > > > + return;
> > > >
> > > > When does en_print ever get false?
> > > Once the events printed, it will be set false (pls find at the last
> > > line of this function).
> >
> > What is the point of making en_print a static variable? We print all the time
> > when we have a global event anyway.
>
> Hi Liviu:
>
> | why make en_print a static.
>
> Consider you commit a scene which may leads a UNDERUN. and it will
> trigger HW UNDERRUN in every vsync peroid untill this sceen have been
> replace by another scene. for a scene it will trigger same error again
> and again. we don't need print them all for a scene one msg is enough.

The same can be achieved by removing en_print entirely and inverting the top
condition:

if (!evts->global && !is_new_frame(evts))
return;
>
> | we print all the time when we have a global event.
> Since we only reduce the duplicate error, but want print all different error.
> And per our HW design, the event reported by different component.
> this global for collect the GCU error. the pipeline_event is for
> LPU/CU/DOU. like UNDERUN which is only DOU error.
>
> and current GCU only have one error type: opmode change error which only
> can be happened on when we call change_opmode in crtc_enable/disable.
>
> So don't worry, globl event which can not make en_print has been set to
> true in every irq handling.

And that's the reason I'm asking why make en_print static if we reset it in
every irq_handling (i.e. when we actually want to print). Does it really need
to be static when we don't actually use the stored state?

Best regards,
Liviu


>
> Thanks
> James
>
> >
> > > > > +
> > > > > +#ifdef DEBUG
> > > > > + print_evts |= KOMEDA_WARN_EVENTS;
> > > > > +#endif
> > > > > +
> > > > > + if ((evts->global | evts->pipes[0] | evts->pipes[1]) & print_evts) {
> > > > > + #define STR_SZ 128
> > > > > + char msg[STR_SZ];
> > > >
> > > > I've counted about 27 evt_sprintf() calls in evt_str() function, with an
> > > > average of 5 characters each, so thats 135 characters printed into a buffer
> > > > that is only 128 bytes. Please don't do this!
> > > komeda_sprintf() will check the size and also I thought those evt
> > > will not populat together. But yes, I'd better change this to 256.
> > > Will change this.
> > >
> > > > > + struct komeda_str str;
> > > > > +
> > > > > + str.str = msg;
> > > > > + str.sz = STR_SZ;
> > > > > + str.len = 0;
> > > > > +
> > > > > + komeda_sprintf(&str, "gcu: ");
> > > > > + evt_str(&str, evts->global);
> > > > > + komeda_sprintf(&str, ", pipes[0]: ");
> > > > > + evt_str(&str, evts->pipes[0]);
> > > > > + komeda_sprintf(&str, ", pipes[1]: ");
> > > > > + evt_str(&str, evts->pipes[1]);
> > > > > +
> > > > > + DRM_ERROR("err detect: %s\n", msg);
> > > > > +
> > > > > + en_print = false;
> > > > > + }
> > > > > +}
> > > > > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > > > > index 647bce5..1462bac 100644
> > > > > --- a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > > > > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > > > > @@ -47,6 +47,8 @@ static irqreturn_t komeda_kms_irq_handler(int irq, void *data)
> > > > > memset(&evts, 0, sizeof(evts));
> > > > > status = mdev->funcs->irq_handler(mdev, &evts);
> > > > >
> > > > > + komeda_print_events(&evts);
> > > >
> > > > Calling this function from the IRQ handler is a bad idea. We should use debugfs
> > > > if you really want to have a trace of the events, but I personally don't see
> > > > value in having this functionality in the kernel at all. You can expose the
> > > > value of the evts->global and evts->pipes[] as integers and decode that in
> > > > userspace or as a debugfs entry.
> > > >
> > > > Best regards,
> > > > Liviu
> > >
> > > The name of this function is misleading, but this is printing out the
> > > hardware detected errors, from which we can know directly once the
> > > errors happened on the hardware. Like if the driver code was at
> > > bring-up stage, the logs from this layer is helpful. So can we keep
> > > this?
> >
> > We should probably just collect the global and pipes values and expose
> > them to userspace so that the printing and decoding of the messages happens
> > there.
> >
> > Best regards,
> > Liviu
>
> Hi Liviu:
>
> Any special resons.
>
> Since such error print is not only wanted by us, mostly it is required
> and used by our customer to easily capture the problem.
> If no special reasons, I want to keep it for avoiding the complaint
> from our customer.
>
> Thanks
> James
> >
> > >
> > > Best regards,
> > > Lowry
> > >
> > > > > +
> > > > > /* Notify the crtc to handle the events */
> > > > > for (i = 0; i < kms->n_crtcs; i++)
> > > > > komeda_crtc_handle_event(&kms->crtcs[i], &evts);
> > > > > --
> > > > > 1.9.1
> > > > >
> > > >
> > > > --
> > > > ====================
> > > > | I would like to |
> > > > | fix the world, |
> > > > | but they're not |
> > > > | giving me the |
> > > > \ source code! /
> > > > ---------------
> > > > ¯\_(ツ)_/¯
> > >
> > > --
> > > Regards,
> > > Lowry
> >
> > --
> > ====================
> > | I would like to |
> > | fix the world, |
> > | but they're not |
> > | giving me the |
> > \ source code! /
> > ---------------
> > ¯\_(ツ)_/¯

--
====================
| I would like to |
| fix the world, |
| but they're not |
| giving me the |
\ source code! /
---------------
¯\_(ツ)_/¯
\
 
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