RE: [PATCH v1 1/1] mlxbf-bootctl: Add sysfs file for BlueField boot log

[Liming Sun]

> -----Original Message-----
> From: Hans de Goede <hdegoede@xxxxxxxxxx>
> Sent: Tuesday, May 9, 2023 6:07 AM
> To: Liming Sun <limings@xxxxxxxxxx>; Vadim Pasternak
> <vadimp@xxxxxxxxxx>; David Thompson <davthompson@xxxxxxxxxx>; Mark
> Gross <markgross@xxxxxxxxxx>
> Cc: platform-driver-x86@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v1 1/1] mlxbf-bootctl: Add sysfs file for BlueField boot log
> 
> Hi,
> 
> On 5/8/23 20:01, Liming Sun wrote:
> > This commit adds sysfs interface to be used to write into the
> > boot log which is 1KB HW buffer on BlueField SoC. The same log
> > buffer is also used by firmware code like ATF/UEFI, and can be
> > displayed by userspace tools or from external host via USB/PCIe.
> >
> > Signed-off-by: Liming Sun <limings@xxxxxxxxxx>
> > Reviewed-by: Vadim Pasternak <vadimp@xxxxxxxxxx>
> 
> Vadim, David, I would appreciate if one of you could also
> take a look at this patch.

v2 has been posted with internal review with Vadim.

> 
> > ---
> >  .../testing/sysfs-platform-mellanox-bootctl   |   7 +
> >  drivers/platform/mellanox/mlxbf-bootctl.c     | 141 ++++++++++++++++++
> >  2 files changed, 148 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
> b/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
> > index 9b99a81babb1..239184db57dd 100644
> > --- a/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
> > +++ b/Documentation/ABI/testing/sysfs-platform-mellanox-bootctl
> > @@ -75,3 +75,10 @@ KernelVersion:	6.4
> >  Contact:	"Liming Sun <limings@xxxxxxxxxx>"
> >  Description:
> >  		The file used to access the BlueField boot fifo.
> > +
> > +What:		/sys/bus/platform/devices/MLNXBF04:00/rsh_log
> > +Date:		May 2023
> > +KernelVersion:	6.4
> > +Contact:	"Liming Sun <limings@xxxxxxxxxx>"
> > +Description:
> > +		The file used to access the BlueField boot log.
> 
> Access suggests reading, but this is a write-only file please make this more
> clear.

Updated in v2 to clarify it's for write.

> 
> Also please document the accepted prefixes for log levels here / document
> the log format.

Updated in v2 with more details about the log format.

> 
> > diff --git a/drivers/platform/mellanox/mlxbf-bootctl.c
> b/drivers/platform/mellanox/mlxbf-bootctl.c
> > index 1bad1d278672..c02062cb3128 100644
> > --- a/drivers/platform/mellanox/mlxbf-bootctl.c
> > +++ b/drivers/platform/mellanox/mlxbf-bootctl.c
> > @@ -45,10 +45,38 @@ static const char * const
> mlxbf_bootctl_lifecycle_states[] = {
> >  	[3] = "RMA",
> >  };
> >
> > +/* Log header format. */
> > +#define MLXBF_RSH_LOG_TYPE_SHIFT	56
> > +#define MLXBF_RSH_LOG_LEN_SHIFT		48
> > +#define MLXBF_RSH_LOG_LEVEL_SHIFT	0
> > +
> > +/* Log module ID and type (only MSG type in Linux driver for now). */
> > +#define MLXBF_RSH_LOG_TYPE_MSG		0x04ULL
> > +
> > +/* Log ctl/data register offset. */
> > +#define MLXBF_RSH_SCRATCH_BUF_CTL_OFF	0
> > +#define MLXBF_RSH_SCRATCH_BUF_DATA_OFF	0x10
> > +
> > +/* Log message levels. */
> > +enum {
> > +	MLXBF_RSH_LOG_INFO,
> > +	MLXBF_RSH_LOG_WARN,
> > +	MLXBF_RSH_LOG_ERR
> > +};
> > +
> >  /* Mapped pointer for RSH_BOOT_FIFO_DATA and RSH_BOOT_FIFO_COUNT
> register. */
> >  static void __iomem *mlxbf_rsh_boot_data;
> >  static void __iomem *mlxbf_rsh_boot_cnt;
> >
> > +/* Mapped pointer for rsh log semaphore/ctrl/data register. */
> > +static void __iomem *mlxbf_rsh_semaphore;
> > +static void __iomem *mlxbf_rsh_scratch_buf_ctl;
> > +static void __iomem *mlxbf_rsh_scratch_buf_data;
> > +
> > +/* Rsh log levels. */
> > +static const char * const mlxbf_rsh_log_level[] = {
> > +	"INFO", "WARN", "ERR", "ASSERT"};
> > +
> >  /* ARM SMC call which is atomic and no need for lock. */
> >  static int mlxbf_bootctl_smc(unsigned int smc_op, int smc_arg)
> >  {
> > @@ -266,12 +294,111 @@ static ssize_t fw_reset_store(struct device *dev,
> >  	return count;
> >  }
> >
> > +/* Size(8-byte words) of the log buffer. */
> > +#define RSH_SCRATCH_BUF_CTL_IDX_MASK	0x7f
> > +
> > +static int mlxbf_rsh_log_sem_lock(void)
> > +{
> > +	unsigned long timeout;
> > +
> > +	/* Take the semaphore. */
> > +	timeout = jiffies + msecs_to_jiffies(100);
> > +	while (readq(mlxbf_rsh_semaphore)) {
> > +		if (time_after(jiffies, timeout))
> > +			return -ETIMEDOUT;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static void mlxbf_rsh_log_sem_unlock(void)
> > +{
> > +	writeq(0, mlxbf_rsh_semaphore);
> > +}
> > +
> > +static ssize_t rsh_log_store(struct device *dev,
> > +			     struct device_attribute *attr,
> > +			     const char *buf, size_t count)
> > +{
> > +	int rc, idx, num, len, size = (int)count, level = MLXBF_RSH_LOG_INFO;
> > +	u64 data;
> > +
> > +	if (!size)
> > +		return -EINVAL;
> > +
> > +	if (!mlxbf_rsh_semaphore || !mlxbf_rsh_scratch_buf_ctl)
> > +		return -EOPNOTSUPP;
> > +
> > +	/* Ignore line break at the end. */
> > +	if (buf[size - 1] == 0xa)
> 
> Please replace 0x0a with '\n' .

Updated in v2

> 
> > +		size--;
> > +
> > +	/* Check the message prefix. */
> > +	for (idx = 0; idx < ARRAY_SIZE(mlxbf_rsh_log_level); idx++) {
> > +		len = strlen(mlxbf_rsh_log_level[idx]);
> > +		if (len + 1 < size &&
> > +		    !strncmp(buf, mlxbf_rsh_log_level[idx], len)) {
> > +			buf += len + 1;
> 
> Why len + 1, this seems intended to assume some separator
> between prefix and the actual message?  But if that is
> the case please also check that the expected separator
> character is there.

Good catch. Updated in v2 to remove the '+ 1" which causes confusing.
The separator logic is already covered in next code block.

> 
> Otherwise this looks good to me.
> 
> Regards,
> 
> Hans
> 
> 
> 
> > +			size -= len + 1;
> > +			level = idx;
> > +			break;
> > +		}
> > +	}
> > +
> > +	/* Ignore leading spaces. */
> > +	while (size > 0 && buf[0] == ' ') {
> > +		size--;
> > +		buf++;
> > +	}
> > +
> > +	/* Take the semaphore. */
> > +	rc = mlxbf_rsh_log_sem_lock();
> > +	if (rc)
> > +		return rc;
> > +
> > +	/* Calculate how many words are available. */
> > +	num = (size + sizeof(u64) - 1) / sizeof(u64);
> > +	idx = readq(mlxbf_rsh_scratch_buf_ctl);
> > +	if (idx + num + 1 >= RSH_SCRATCH_BUF_CTL_IDX_MASK)
> > +		num = RSH_SCRATCH_BUF_CTL_IDX_MASK - idx - 1;
> > +	if (num <= 0)
> > +		goto done;
> > +
> > +	/* Write Header. */
> > +	data = (MLXBF_RSH_LOG_TYPE_MSG <<
> MLXBF_RSH_LOG_TYPE_SHIFT) |
> > +		((u64)num << MLXBF_RSH_LOG_LEN_SHIFT) |
> > +		((u64)level << MLXBF_RSH_LOG_LEVEL_SHIFT);
> > +	writeq(data, mlxbf_rsh_scratch_buf_data);
> > +
> > +	/* Write message. */
> > +	for (idx = 0, len = size; idx < num && len > 0; idx++) {
> > +		if (len <= sizeof(u64)) {
> > +			data = 0;
> > +			memcpy(&data, buf, len);
> > +			len = 0;
> > +		} else {
> > +			memcpy(&data, buf, sizeof(u64));
> > +			len -= sizeof(u64);
> > +			buf += sizeof(u64);
> > +		}
> > +		writeq(data, mlxbf_rsh_scratch_buf_data);
> > +	}
> > +
> > +done:
> > +	/* Release the semaphore. */
> > +	mlxbf_rsh_log_sem_unlock();
> > +
> > +	/* Ignore the rest if no more space. */
> > +	return count;
> > +}
> > +
> >  static DEVICE_ATTR_RW(post_reset_wdog);
> >  static DEVICE_ATTR_RW(reset_action);
> >  static DEVICE_ATTR_RW(second_reset_action);
> >  static DEVICE_ATTR_RO(lifecycle_state);
> >  static DEVICE_ATTR_RO(secure_boot_fuse_state);
> >  static DEVICE_ATTR_WO(fw_reset);
> > +static DEVICE_ATTR_WO(rsh_log);
> >
> >  static struct attribute *mlxbf_bootctl_attrs[] = {
> >  	&dev_attr_post_reset_wdog.attr,
> > @@ -280,6 +407,7 @@ static struct attribute *mlxbf_bootctl_attrs[] = {
> >  	&dev_attr_lifecycle_state.attr,
> >  	&dev_attr_secure_boot_fuse_state.attr,
> >  	&dev_attr_fw_reset.attr,
> > +	&dev_attr_rsh_log.attr,
> >  	NULL
> >  };
> >
> > @@ -345,6 +473,7 @@ static bool mlxbf_bootctl_guid_match(const guid_t
> *guid,
> >  static int mlxbf_bootctl_probe(struct platform_device *pdev)
> >  {
> >  	struct arm_smccc_res res = { 0 };
> > +	void __iomem *reg;
> >  	guid_t guid;
> >  	int ret;
> >
> > @@ -358,6 +487,18 @@ static int mlxbf_bootctl_probe(struct
> platform_device *pdev)
> >  	if (IS_ERR(mlxbf_rsh_boot_cnt))
> >  		return PTR_ERR(mlxbf_rsh_boot_cnt);
> >
> > +	/* Get the resource of the bootfifo counter register. */
> > +	mlxbf_rsh_semaphore = devm_platform_ioremap_resource(pdev, 2);
> > +	if (IS_ERR(mlxbf_rsh_semaphore))
> > +		return PTR_ERR(mlxbf_rsh_semaphore);
> > +
> > +	/* Get the resource of the bootfifo counter register. */
> > +	reg = devm_platform_ioremap_resource(pdev, 3);
> > +	if (IS_ERR(reg))
> > +		return PTR_ERR(reg);
> > +	mlxbf_rsh_scratch_buf_ctl = reg +
> MLXBF_RSH_SCRATCH_BUF_CTL_OFF;
> > +	mlxbf_rsh_scratch_buf_data = reg +
> MLXBF_RSH_SCRATCH_BUF_DATA_OFF;
> > +
> >  	/* Ensure we have the UUID we expect for this service. */
> >  	arm_smccc_smc(MLXBF_BOOTCTL_SIP_SVC_UID, 0, 0, 0, 0, 0, 0, 0,
> &res);
> >  	guid_parse(mlxbf_bootctl_svc_uuid_str, &guid);