Re: [PATCH 05/17] coresight: Add support for TMC ETR SG unit

[Suzuki K Poulose]

> > diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > index 4b9e2b276122..4424eb67a54c 100644
> > --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> > @@ -21,6 +21,89 @@
> > Â #include "coresight-tmc.h"
> > Â /*
> > + * The TMC ETR SG has a page size of 4K. The SG table contains pointers
> > + * to 4KB buffers. However, the OS may be use PAGE_SIZE different from
>
> nit:
> "the OS may use a PAGE_SIZE different from".


> > +#define ETR_SG_PAGE_SHIFTÂÂÂÂÂÂÂ 12
> > +#define ETR_SG_PAGE_SIZEÂÂÂÂÂÂÂ (1UL << ETR_SG_PAGE_SHIFT)
> > +#define ETR_SG_PAGES_PER_SYSPAGEÂÂÂ (1UL << \
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (PAGE_SHIFT - ETR_SG_PAGE_SHIFT))
>
> I think this would be slightly easier to understand if defined as:
> "(PAGE_SIZE / ETR_SG_PAGE_SIZE)".

> > +/* Dump the given sg_table */
> > +static void tmc_etr_sg_table_dump(struct etr_sg_table *etr_table)
> > +{
> > +ÂÂÂ sgte_t *ptr;
> > +ÂÂÂ int i = 0;
> > +ÂÂÂ dma_addr_t addr;
> > +ÂÂÂ struct tmc_sg_table *sg_table = etr_table->sg_table;
> > +
> > +ÂÂÂ ptr = (sgte_t *)tmc_sg_daddr_to_vaddr(sg_table,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ etr_table->hwaddr, true);
> > +ÂÂÂ while (ptr) {
> > +ÂÂÂÂÂÂÂ addr = ETR_SG_ADDR(*ptr);
> > +ÂÂÂÂÂÂÂ switch (ETR_SG_ET(*ptr)) {
> > +ÂÂÂÂÂÂÂ case ETR_SG_ET_NORMAL:
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("%05d: %p\t:[N] 0x%llx\n", i, ptr, addr);
> > +ÂÂÂÂÂÂÂÂÂÂÂ ptr++;
> > +ÂÂÂÂÂÂÂÂÂÂÂ break;
> > +ÂÂÂÂÂÂÂ case ETR_SG_ET_LINK:
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("%05d: *** %p\t:{L} 0x%llx ***\n",
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ i, ptr, addr);
> > +ÂÂÂÂÂÂÂÂÂÂÂ ptr = (sgte_t *)tmc_sg_daddr_to_vaddr(sg_table,
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ addr, true);
> > +ÂÂÂÂÂÂÂÂÂÂÂ break;
> > +ÂÂÂÂÂÂÂ case ETR_SG_ET_LAST:
> > +ÂÂÂÂÂÂÂÂÂÂÂ pr_debug("%05d: ### %p\t:[L] 0x%llx ###\n",
> > +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ i, ptr, addr);
> > +ÂÂÂÂÂÂÂÂÂÂÂ return;
>
> I get this is debug code, but it seems like if ETR_SG_ET(*ptr) is 0 we get stuck in an infinite loop. I guess it is something that supposedly doesn't happen, still I'd prefer having a default case saying the table might be corrupted and either incrementing ptr to try and get more info or breaking out of the loop.

> > +ÂÂÂÂÂÂÂ }
> > +ÂÂÂÂÂÂÂ i++;
> > +ÂÂÂ }
> > +ÂÂÂ pr_debug("******* End of Table *****\n");
> > +}
> > +#endif
> > +
> > +/*
> > + * Populate the SG Table page table entries from table/data
> > + * pages allocated. Each Data page has ETR_SG_PAGES_PER_SYSPAGE SG pages.
> > + * So does a Table page. So we keep track of indices of the tables
> > + * in each system page and move the pointers accordingly.
> > + */
> > +#define INC_IDX_ROUND(idx, size) (idx = (idx + 1) % size)
>
> Needs more parenthesis around idx and size.

> > +static void tmc_etr_sg_table_populate(struct etr_sg_table *etr_table)
> > +{
> > +ÂÂÂ dma_addr_t paddr;
> > +ÂÂÂ int i, type, nr_entries;
> > +ÂÂÂ int tpidx = 0; /* index to the current system table_page */
> > +ÂÂÂ int sgtidx = 0;ÂÂÂ /* index to the sg_table within the current syspage */
> > +ÂÂÂ int sgtoffset = 0; /* offset to the next entry within the sg_table */
>
> That's misleading, this seems to be the index of an entry within an ETR_SG_PAGE rather than an offset in bytes.
>
> Maybe ptridx or entryidx would be a better name.

You're right, I have chosen sgtentry for now.

Thanks for the detailed look, I will fix all of them.

Cheers
Suzuki