Subject: Re: [PATCH 3/4] remoteproc: add support for a new 64-bit trace version

From: Bjorn Andersson <[email-masked]>
Date: Thu, 21 May 2020 11:04:17 -0700

On Wed 25 Mar 13:47 PDT 2020, Suman Anna wrote:

> Introduce a new trace entry resource structure that accommodates
> a 64-bit device address to support 64-bit processors. This is to
> be used using an overloaded version value of 1 in the upper 32-bits
> of the previous resource type field. The new resource still uses
> 32-bits for the length field (followed by a 32-bit reserved field,
> so can be updated in the future), which is a sufficiently large
> trace buffer size. A 32-bit padding field also had to be added
> to align the device address on a 64-bit boundary, and match the
> usage on the firmware side.
> 
> The remoteproc debugfs logic also has been adjusted accordingly.
> 
> Signed-off-by: Suman Anna <[email-masked]>
> ---
>  drivers/remoteproc/remoteproc_core.c    | 40 ++++++++++++++++++++-----
>  drivers/remoteproc/remoteproc_debugfs.c | 37 ++++++++++++++++++-----
>  include/linux/remoteproc.h              | 26 ++++++++++++++++
>  3 files changed, 87 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 53bc37c508c6..b9a097990862 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -609,21 +609,45 @@ void rproc_vdev_release(struct kref *ref)
>   *
>   * Returns 0 on success, or an appropriate error code otherwise
>   */
> -static int rproc_handle_trace(struct rproc *rproc, struct fw_rsc_trace *rsc,
> +static int rproc_handle_trace(struct rproc *rproc, void *rsc,
>  			      int offset, int avail, u16 ver)
>  {
>  	struct rproc_debug_trace *trace;
>  	struct device *dev = &rproc->dev;
> +	struct fw_rsc_trace *rsc1;
> +	struct fw_rsc_trace2 *rsc2;
>  	char name[15];
> +	size_t rsc_size;
> +	u32 reserved;
> +	u64 da;
> +	u32 len;
> +
> +	if (!ver) {

This looks like a switch to me, but I also do think this looks rather
crude, if you spin off the tail of this function and call it from a
rproc_handle_trace() and rproc_handle_trace64() I believe this would be
cleaner.

> +		rsc1 = (struct fw_rsc_trace *)rsc;
> +		rsc_size = sizeof(*rsc1);
> +		reserved = rsc1->reserved;
> +		da = rsc1->da;
> +		len = rsc1->len;
> +	} else if (ver == 1) {
> +		rsc2 = (struct fw_rsc_trace2 *)rsc;
> +		rsc_size = sizeof(*rsc2);
> +		reserved = rsc2->reserved;
> +		da = rsc2->da;
> +		len = rsc2->len;
> +	} else {
> +		dev_err(dev, "unsupported trace rsc version %d\n", ver);

If we use "type" to describe your 64-bit-da-trace then this sanity check
would have been taken care of by the core.

> +		return -EINVAL;
> +	}
>  
> -	if (sizeof(*rsc) > avail) {
> +	if (rsc_size > avail) {
>  		dev_err(dev, "trace rsc is truncated\n");
>  		return -EINVAL;
>  	}
>  
>  	/* make sure reserved bytes are zeroes */
> -	if (rsc->reserved) {
> -		dev_err(dev, "trace rsc has non zero reserved bytes\n");
> +	if (reserved) {
> +		dev_err(dev, "trace rsc has non zero reserved bytes, value = 0x%x\n",
> +			reserved);
>  		return -EINVAL;
>  	}
>  
> @@ -632,8 +656,8 @@ static int rproc_handle_trace(struct rproc *rproc, struct fw_rsc_trace *rsc,
>  		return -ENOMEM;
>  
>  	/* set the trace buffer dma properties */
> -	trace->trace_mem.len = rsc->len;
> -	trace->trace_mem.da = rsc->da;
> +	trace->trace_mem.len = len;
> +	trace->trace_mem.da = da;
>  
>  	/* set pointer on rproc device */
>  	trace->rproc = rproc;
> @@ -652,8 +676,8 @@ static int rproc_handle_trace(struct rproc *rproc, struct fw_rsc_trace *rsc,
>  
>  	rproc->num_traces++;
>  
> -	dev_dbg(dev, "%s added: da 0x%x, len 0x%x\n",
> -		name, rsc->da, rsc->len);
> +	dev_dbg(dev, "%s added: da 0x%llx, len 0x%x\n",
> +		name, da, len);
>  
>  	return 0;
>  }
> diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
> index 3560eed7a360..ff43736db45a 100644
> --- a/drivers/remoteproc/remoteproc_debugfs.c
> +++ b/drivers/remoteproc/remoteproc_debugfs.c
> @@ -192,7 +192,8 @@ static int rproc_rsc_table_show(struct seq_file *seq, void *p)
>  	struct resource_table *table = rproc->table_ptr;
>  	struct fw_rsc_carveout *c;
>  	struct fw_rsc_devmem *d;
> -	struct fw_rsc_trace *t;
> +	struct fw_rsc_trace *t1;
> +	struct fw_rsc_trace2 *t2;
>  	struct fw_rsc_vdev *v;
>  	int i, j;
>  
> @@ -205,6 +206,7 @@ static int rproc_rsc_table_show(struct seq_file *seq, void *p)
>  		int offset = table->offset[i];
>  		struct fw_rsc_hdr *hdr = (void *)table + offset;
>  		void *rsc = (void *)hdr + sizeof(*hdr);
> +		u16 ver = hdr->st.v;
>  
>  		switch (hdr->st.t) {
>  		case RSC_CARVEOUT:
> @@ -230,13 +232,32 @@ static int rproc_rsc_table_show(struct seq_file *seq, void *p)
>  			seq_printf(seq, "  Name %s\n\n", d->name);
>  			break;
>  		case RSC_TRACE:
> -			t = rsc;
> -			seq_printf(seq, "Entry %d is of type %s\n",
> -				   i, types[hdr->st.t]);
> -			seq_printf(seq, "  Device Address 0x%x\n", t->da);
> -			seq_printf(seq, "  Length 0x%x Bytes\n", t->len);
> -			seq_printf(seq, "  Reserved (should be zero) [%d]\n", t->reserved);
> -			seq_printf(seq, "  Name %s\n\n", t->name);
> +			if (ver == 0) {

Again, this is a switch, here in a switch. Just defining a new
RSC_TRACE64 type would reduce the amount of code here...

> +				t1 = rsc;
> +				seq_printf(seq, "Entry %d is version %d of type %s\n",
> +					   i, ver, types[hdr->st.t]);
> +				seq_printf(seq, "  Device Address 0x%x\n",
> +					   t1->da);
> +				seq_printf(seq, "  Length 0x%x Bytes\n",
> +					   t1->len);
> +				seq_printf(seq, "  Reserved (should be zero) [%d]\n",
> +					   t1->reserved);
> +				seq_printf(seq, "  Name %s\n\n", t1->name);
> +			} else if (ver == 1) {
> +				t2 = rsc;
> +				seq_printf(seq, "Entry %d is version %d of type %s\n",
> +					   i, ver, types[hdr->st.t]);
> +				seq_printf(seq, "  Device Address 0x%llx\n",
> +					   t2->da);
> +				seq_printf(seq, "  Length 0x%x Bytes\n",
> +					   t2->len);
> +				seq_printf(seq, "  Reserved (should be zero) [%d]\n",
> +					   t2->reserved);
> +				seq_printf(seq, "  Name %s\n\n", t2->name);
> +			} else {
> +				seq_printf(seq, "Entry %d is an unsupported version %d of type %s\n",
> +					   i, ver, types[hdr->st.t]);
> +			}
>  			break;
>  		case RSC_VDEV:
>  			v = rsc;
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 526d3cb45e37..3b3bea42f8b1 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -243,6 +243,32 @@ struct fw_rsc_trace {
>  	u8 name[32];
>  } __packed;
>  
> +/**
> + * struct fw_rsc_trace2 - trace buffer declaration supporting 64-bits
> + * @padding: initial padding after type field for aligned 64-bit access
> + * @da: device address (64-bit)
> + * @len: length (in bytes)
> + * @reserved: reserved (must be zero)
> + * @name: human-readable name of the trace buffer
> + *
> + * This resource entry is an enhanced version of the fw_rsc_trace resourec entry
> + * and the provides equivalent functionality but designed for 64-bit remote
> + * processors.
> + *
> + * @da specifies the device address of the buffer, @len specifies
> + * its size, and @name may contain a human readable name of the trace buffer.
> + *
> + * After booting the remote processor, the trace buffers are exposed to the
> + * user via debugfs entries (called trace0, trace1, etc..).
> + */
> +struct fw_rsc_trace2 {

Sounds more like fw_rsc_trace64 to me - in particular since the version
of trace2 is 1...

> +	u32 padding;
> +	u64 da;
> +	u32 len;
> +	u32 reserved;

What's the purpose of this reserved field?

Regards,
Bjorn

> +	u8 name[32];
> +} __packed;
> +
>  /**
>   * struct fw_rsc_vdev_vring - vring descriptor entry
>   * @da: device address
> -- 
> 2.23.0
> 

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