Re: [PATCH] drm/komeda: Adds error event print functionality

[Mihail Atanassov]

Hi Lowry,

On Thursday, 1 August 2019 12:37:15 BST Lowry Li (Arm Technology China) wrote:
> From: "Lowry Li (Arm Technology China)" <Lowry.Li@xxxxxxx>
> 
> Adds to print the event message when error happens and the same event
> will not be printed until next vsync.
> 
> Changes since v1:
> 1. Handling the event print by CONFIG_KOMEDA_ERROR_PRINT;
> 2. Changing the max string size to 256.
> 
> Signed-off-by: Lowry Li (Arm Technology China) <lowry.li@xxxxxxx>
> ---
>  drivers/gpu/drm/arm/display/Kconfig               |   6 +
>  drivers/gpu/drm/arm/display/komeda/Makefile       |   2 +
>  drivers/gpu/drm/arm/display/komeda/komeda_dev.h   |  15 +++
>  drivers/gpu/drm/arm/display/komeda/komeda_event.c | 141
> ++++++++++++++++++++++ drivers/gpu/drm/arm/display/komeda/komeda_kms.c   | 
>  4 +
>  5 files changed, 168 insertions(+)
>  create mode 100644 drivers/gpu/drm/arm/display/komeda/komeda_event.c
> 
> diff --git a/drivers/gpu/drm/arm/display/Kconfig
> b/drivers/gpu/drm/arm/display/Kconfig index cec0639..e87ff86 100644
> --- a/drivers/gpu/drm/arm/display/Kconfig
> +++ b/drivers/gpu/drm/arm/display/Kconfig
> @@ -12,3 +12,9 @@ config DRM_KOMEDA
>  	  Processor driver. It supports the D71 variants of the hardware.
> 
>  	  If compiled as a module it will be called komeda.
> +
> +config DRM_KOMEDA_ERROR_PRINT
> +	bool "Enable komeda error print"
> +	depends on DRM_KOMEDA
> +	help
> +	  Choose this option to enable error printing.
> diff --git a/drivers/gpu/drm/arm/display/komeda/Makefile
> b/drivers/gpu/drm/arm/display/komeda/Makefile index 5c3900c..f095a1c 100644
> --- a/drivers/gpu/drm/arm/display/komeda/Makefile
> +++ b/drivers/gpu/drm/arm/display/komeda/Makefile
> @@ -22,4 +22,6 @@ komeda-y += \
>  	d71/d71_dev.o \
>  	d71/d71_component.o
> 
> +komeda-$(CONFIG_DRM_KOMEDA_ERROR_PRINT) += komeda_event.o
> +
>  obj-$(CONFIG_DRM_KOMEDA) += komeda.o
> diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_dev.h
> b/drivers/gpu/drm/arm/display/komeda/komeda_dev.h index d1c86b6..e28e7e6
> 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,
> @@ -207,4 +218,8 @@ struct komeda_dev {
> 
>  struct komeda_dev *dev_to_mdev(struct device *dev);
> 
> +#ifdef CONFIG_DRM_KOMEDA_ERROR_PRINT
> +void komeda_print_events(struct komeda_events *evts);
> +#endif
> +
>  #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..57b60cd
> --- /dev/null
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_event.c
> @@ -0,0 +1,141 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * (C) COPYRIGHT 2019 ARM Limited. All rights reserved.
> + * Author: James.Qian.Wang <james.qian.wang@xxxxxxx>
> + *
> + */
> +#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, ...)
The lack of '\0'-termination in the truncation case is quite disconcerting, 
especially since vsnprintf does it. This would be quite surprising to the 
casual passer-by.
> +{
> +	va_list args;
> +	int num, free_sz;
> +	int err;
> +
> +	free_sz = str->sz - str->len;
That's off by 1, you need to account for the null byte.
> +	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) {
Strictly less than. To quote from the doc of vsnprintf: 
""" [...] If the return is greater than or equal to @size, the resulting 
string is truncated. """
> +		str->len += num;
> +		err = 0;
> +	} else {
> +		str->len = str->sz;
Off by 1 here, too.
> +		err = -ENOSPC;
That error code isn't used anywhere, so there's no value to having it in the 
current version of this patch. Either check the error code somewhere 
downstream and handle it, or change that to an actionable message for the 
person reading the kernel log. As it stands truncation is completely silent.
> +	}
> +
> +	return err;
> +}
> +
> +static void evt_sprintf(struct komeda_str *str, u64 evt, const char *msg)
> +{
> +	if (evt)
> +		komeda_sprintf(str, msg);
> +}
> +
> +static void evt_str(struct komeda_str *str, u64 events)
> +{
> +	if (events == 0ULL) {
> +		evt_sprintf(str, 1, "None");
[nit] Call `komeda_sprintf(str, "None")` directly?
> +		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 | KOMEDA_EVENT_EOW);
> +}
> +
> +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;
> +
> +	if ((evts->global | evts->pipes[0] | evts->pipes[1]) & print_evts) 
{
> +		#define STR_SZ		256
[nit] I'd undef that once it's no longer needed
> +		char msg[STR_SZ];
> +		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 419a8b0..0fafc36
> 100644
> --- a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> +++ b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> @@ -47,6 +47,10 @@ static irqreturn_t komeda_kms_irq_handler(int irq, void
> *data) memset(&evts, 0, sizeof(evts));
>  	status = mdev->funcs->irq_handler(mdev, &evts);
> 
> +#ifdef CONFIG_DRM_KOMEDA_ERROR_PRINT
> +	komeda_print_events(&evts);
> +#endif
> +
>  	/* Notify the crtc to handle the events */
>  	for (i = 0; i < kms->n_crtcs; i++)
>  		komeda_crtc_handle_event(&kms->crtcs[i], &evts);

BR,
Mihail