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SubjectRe: [PATCH v2 18/27] coresight: catu: Add support for scatter gather tables
On 8 May 2018 at 09:56, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
> On 07/05/18 21:25, Mathieu Poirier wrote:
>>
>> On Tue, May 01, 2018 at 10:10:48AM +0100, Suzuki K Poulose wrote:
>>>
>>> This patch adds the support for setting up a SG table for use
>>> by the CATU. We reuse the tmc_sg_table to represent the table/data
>>> pages, even though the table format is different.
>>>
>
> ...
>
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-catu.c
>>> b/drivers/hwtracing/coresight/coresight-catu.c
>>> index 2cd69a6..4cc2928 100644
>>> --- a/drivers/hwtracing/coresight/coresight-catu.c
>>> +++ b/drivers/hwtracing/coresight/coresight-catu.c
>>> @@ -16,10 +16,419 @@
>
>
> ...
>
>>> +
>>> +/*
>>> + * Update the valid bit for a given range of indices [start, end)
>>> + * in the given table @table.
>>> + */
>>> +static inline void catu_update_state_range(cate_t *table, int start,
>>> + int end, int valid)
>>
>>
>> Indentation
>>
>
> ...
>
>>> +#ifdef CATU_DEBUG
>>> +static void catu_dump_table(struct tmc_sg_table *catu_table)
>>> +{
>>> + int i;
>>> + cate_t *table;
>>> + unsigned long table_end, buf_size, offset = 0;
>>> +
>>> + buf_size = tmc_sg_table_buf_size(catu_table);
>>> + dev_dbg(catu_table->dev,
>>> + "Dump table %p, tdaddr: %llx\n",
>>> + catu_table, catu_table->table_daddr);
>>> +
>>> + while (offset < buf_size) {
>>> + table_end = offset + SZ_1M < buf_size ?
>>> + offset + SZ_1M : buf_size;
>>> + table = catu_get_table(catu_table, offset, NULL);
>>> + for (i = 0; offset < table_end; i++, offset +=
>>> CATU_PAGE_SIZE)
>>> + dev_dbg(catu_table->dev, "%d: %llx\n", i,
>>> table[i]);
>>> + dev_dbg(catu_table->dev, "Prev : %llx, Next: %llx\n",
>>> + table[CATU_LINK_PREV], table[CATU_LINK_NEXT]);
>>> + dev_dbg(catu_table->dev, "== End of sub-table ===");
>>> + }
>>> + dev_dbg(catu_table->dev, "== End of Table ===");
>>> +}
>>> +
>>> +#else
>>> +static inline void catu_dump_table(struct tmc_sg_table *catu_table)
>>> +{
>>> +}
>>> +#endif
>>
>>
>> I think this approach is better than peppering the code with #ifdefs as it
>> was
>> done for ETR. Please fix that to replicate what you've done here.
>>
>
> OK
>
>>> +
>>> +/*
>>> + * catu_populate_table : Populate the given CATU table.
>>> + * The table is always populated as a circular table.
>>> + * i.e, the "prev" link of the "first" table points to the "last"
>>> + * table and the "next" link of the "last" table points to the
>>> + * "first" table. The buffer should be made linear by calling
>>> + * catu_set_table().
>>> + */
>>> +static void
>>> +catu_populate_table(struct tmc_sg_table *catu_table)
>>> +{
>
>
> ...
>
>>> + while (offset < buf_size) {
>>> + /*
>>> + * The @offset is always 1M aligned here and we have an
>>> + * empty table @table_ptr to fill. Each table can address
>>> + * upto 1MB data buffer. The last table may have fewer
>>> + * entries if the buffer size is not aligned.
>>> + */
>>> + last_offset = (offset + SZ_1M) < buf_size ?
>>> + (offset + SZ_1M) : buf_size;
>>> + for (i = 0; offset < last_offset; i++) {
>>> +
>>> + data_daddr = catu_table->data_pages.daddrs[dpidx]
>>> +
>>> + s_dpidx * CATU_PAGE_SIZE;
>>> +#ifdef CATU_DEBUG
>>> + dev_dbg(catu_table->dev,
>>> + "[table %5d:%03d] 0x%llx\n",
>>> + (offset >> 20), i, data_daddr);
>>> +#endif
>>
>>
>> I'm not a fan of adding #ifdefs in the code like this. I think it is
>> better to
>> have a wrapper (that resolves to nothing if CATU_DEBUG is not defined) and
>> handle the output in there.
>>
>
>
>>> +
>>> + catu_populate_table(catu_table);
>>> + /* Make the buf linear from offset 0 */
>>> + (void)catu_set_table(catu_table, 0, size);
>>> +
>>> + dev_dbg(catu_dev,
>>> + "Setup table %p, size %ldKB, %d table pages\n",
>>> + catu_table, (unsigned long)size >> 10, nr_tpages);
>>
>>
>> I think this should also be wrapped in a special output debug function.
>>
>
> I could do something like :
>
> #ifdef CATU_DEBUG
> #define catu_dbg(fmt, ...) dev_dbg(fmt, __VA_ARGS__)
> #else
> #define catu_dbg(fmt, ...) do { } while (0)
> #endif
>
> And use catu_dbg() for the sprinkled prints.

Yes, that is exactly what I had in mind.

>
> Cheers
> Suzuki

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