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

[Mathieu Poirier]

On 19 October 2017 at 11:15, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote:
> This patch adds support for setting up an SG table used by the
> TMC ETR inbuilt SG unit. The TMC ETR uses 4K page sized tables
> to hold pointers to the 4K data pages with the last entry in a
> table pointing to the next table with the entries, by kind of
> chaining. The 2 LSBs determine the type of the table entry, to
> one of :
>
>  Normal - Points to a 4KB data page.
>  Last   - Points to a 4KB data page, but is the last entry in the
>           page table.
>  Link   - Points to another 4KB table page with pointers to data.
>
> The code takes care of handling the system page size which could
> be different than 4K. So we could end up putting multiple ETR
> SG tables in a single system page, vice versa for the data pages.
>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> ---
>  drivers/hwtracing/coresight/coresight-tmc-etr.c | 256 ++++++++++++++++++++++++
>  1 file changed, 256 insertions(+)
>
> 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 @@
>  #include "coresight-tmc.h"
>
>  /*
> + * 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
> + * 4K (i.e, 16KB or 64KB). This implies that a single OS page could
> + * contain more than one SG buffer and tables.
> + *
> + * A table entry has the following format:
> + *
> + * ---Bit31------------Bit4-------Bit1-----Bit0--
> + * |     Address[39:12]    | SBZ |  Entry Type  |
> + * ----------------------------------------------
> + *
> + * Address: Bits [39:12] of a physical page address. Bits [11:0] are
> + *         always zero.
> + *
> + * Entry type:
> + *     b00 - Reserved.
> + *     b01 - Last entry in the tables, points to 4K page buffer.
> + *     b10 - Normal entry, points to 4K page buffer.
> + *     b11 - Link. The address points to the base of next table.
> + */
> +
> +typedef u32 sgte_t;
> +
> +#define ETR_SG_PAGE_SHIFT              12
> +#define ETR_SG_PAGE_SIZE               (1UL << ETR_SG_PAGE_SHIFT)
> +#define ETR_SG_PAGES_PER_SYSPAGE       (1UL << \
> +                                        (PAGE_SHIFT - ETR_SG_PAGE_SHIFT))
> +#define ETR_SG_PTRS_PER_PAGE           (ETR_SG_PAGE_SIZE / sizeof(sgte_t))
> +#define ETR_SG_PTRS_PER_SYSPAGE                (PAGE_SIZE / sizeof(sgte_t))
> +
> +#define ETR_SG_ET_MASK                 0x3
> +#define ETR_SG_ET_LAST                 0x1
> +#define ETR_SG_ET_NORMAL               0x2
> +#define ETR_SG_ET_LINK                 0x3
> +
> +#define ETR_SG_ADDR_SHIFT              4
> +
> +#define ETR_SG_ENTRY(addr, type) \
> +       (sgte_t)((((addr) >> ETR_SG_PAGE_SHIFT) << ETR_SG_ADDR_SHIFT) | \
> +                (type & ETR_SG_ET_MASK))
> +
> +#define ETR_SG_ADDR(entry) \
> +       (((dma_addr_t)(entry) >> ETR_SG_ADDR_SHIFT) << ETR_SG_PAGE_SHIFT)
> +#define ETR_SG_ET(entry)               ((entry) & ETR_SG_ET_MASK)
> +
> +/*
> + * struct etr_sg_table : ETR SG Table
> + * @sg_table:          Generic SG Table holding the data/table pages.
> + * @hwaddr:            hwaddress used by the TMC, which is the base
> + *                     address of the table.
> + */
> +struct etr_sg_table {
> +       struct tmc_sg_table     *sg_table;
> +       dma_addr_t              hwaddr;
> +};
> +
> +/*
> + * tmc_etr_sg_table_entries: Total number of table entries required to map
> + * @nr_pages system pages.
> + *
> + * We need to map @nr_pages * ETR_SG_PAGES_PER_SYSPAGE data pages.
> + * Each TMC page can map (ETR_SG_PTRS_PER_PAGE - 1) buffer pointers,
> + * with the last entry pointing to the page containing the table

... with the last entry pointing to another page of table entries.  If we ...

> + * entries. If we spill over to a new page for mapping 1 entry,
> + * we could as well replace the link entry of the previous page
> + * with the last entry.
> + */
> +static inline unsigned long __attribute_const__
> +tmc_etr_sg_table_entries(int nr_pages)
> +{
> +       unsigned long nr_sgpages = nr_pages * ETR_SG_PAGES_PER_SYSPAGE;
> +       unsigned long nr_sglinks = nr_sgpages / (ETR_SG_PTRS_PER_PAGE - 1);
> +       /*
> +        * If we spill over to a new page for 1 entry, we could as well
> +        * make it the LAST entry in the previous page, skipping the Link
> +        * address.
> +        */
> +       if (nr_sglinks && (nr_sgpages % (ETR_SG_PTRS_PER_PAGE - 1) < 2))
> +               nr_sglinks--;
> +       return nr_sgpages + nr_sglinks;
> +}
> +
> +/*
>   * tmc_pages_get_offset:  Go through all the pages in the tmc_pages
>   * and map @phys_addr to an offset within the buffer.
>   */
> @@ -307,6 +390,179 @@ ssize_t tmc_sg_table_get_data(struct tmc_sg_table *sg_table,
>         return len;
>  }
>
> +#ifdef ETR_SG_DEBUG
> +/* Map a dma address to virtual address */
> +static unsigned long
> +tmc_sg_daddr_to_vaddr(struct tmc_sg_table *sg_table,
> +                       dma_addr_t addr, bool table)
> +{
> +       long offset;
> +       unsigned long base;
> +       struct tmc_pages *tmc_pages;
> +
> +       if (table) {
> +               tmc_pages = &sg_table->table_pages;
> +               base = (unsigned long)sg_table->table_vaddr;
> +       } else {
> +               tmc_pages = &sg_table->data_pages;
> +               base = (unsigned long)sg_table->data_vaddr;
> +       }
> +
> +       offset = tmc_pages_get_offset(tmc_pages, addr);
> +       if (offset < 0)
> +               return 0;
> +       return base + offset;
> +}
> +
> +/* Dump the given sg_table */
> +static void tmc_etr_sg_table_dump(struct etr_sg_table *etr_table)
> +{
> +       sgte_t *ptr;
> +       int i = 0;
> +       dma_addr_t addr;
> +       struct tmc_sg_table *sg_table = etr_table->sg_table;
> +
> +       ptr = (sgte_t *)tmc_sg_daddr_to_vaddr(sg_table,
> +                                             etr_table->hwaddr, true);
> +       while (ptr) {
> +               addr = ETR_SG_ADDR(*ptr);
> +               switch (ETR_SG_ET(*ptr)) {
> +               case ETR_SG_ET_NORMAL:
> +                       pr_debug("%05d: %p\t:[N] 0x%llx\n", i, ptr, addr);
> +                       ptr++;
> +                       break;
> +               case ETR_SG_ET_LINK:
> +                       pr_debug("%05d: *** %p\t:{L} 0x%llx ***\n",
> +                                i, ptr, addr);
> +                       ptr = (sgte_t *)tmc_sg_daddr_to_vaddr(sg_table,
> +                                                             addr, true);
> +                       break;
> +               case ETR_SG_ET_LAST:
> +                       pr_debug("%05d: ### %p\t:[L] 0x%llx ###\n",
> +                                i, ptr, addr);
> +                       return;
> +               }
> +               i++;
> +       }
> +       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)
> +static void tmc_etr_sg_table_populate(struct etr_sg_table *etr_table)
> +{
> +       dma_addr_t paddr;
> +       int i, type, nr_entries;
> +       int tpidx = 0; /* index to the current system table_page */
> +       int sgtidx = 0; /* index to the sg_table within the current syspage */
> +       int sgtoffset = 0; /* offset to the next entry within the sg_table */
> +       int dpidx = 0; /* index to the current system data_page */
> +       int spidx = 0; /* index to the SG page within the current data page */
> +       sgte_t *ptr; /* pointer to the table entry to fill */
> +       struct tmc_sg_table *sg_table = etr_table->sg_table;
> +       dma_addr_t *table_daddrs = sg_table->table_pages.daddrs;
> +       dma_addr_t *data_daddrs = sg_table->data_pages.daddrs;
> +
> +       nr_entries = tmc_etr_sg_table_entries(sg_table->data_pages.nr_pages);
> +       /*
> +        * Use the contiguous virtual address of the table to update entries.
> +        */
> +       ptr = sg_table->table_vaddr;
> +       /*
> +        * Fill all the entries, except the last entry to avoid special
> +        * checks within the loop.
> +        */
> +       for (i = 0; i < nr_entries - 1; i++) {
> +               if (sgtoffset == ETR_SG_PTRS_PER_PAGE - 1) {
> +                       /*
> +                        * Last entry in a sg_table page is a link address to
> +                        * the next table page. If this sg_table is the last
> +                        * one in the system page, it links to the first
> +                        * sg_table in the next system page. Otherwise, it
> +                        * links to the next sg_table page within the system
> +                        * page.
> +                        */
> +                       if (sgtidx == ETR_SG_PAGES_PER_SYSPAGE - 1) {
> +                               paddr = table_daddrs[tpidx + 1];
> +                       } else {
> +                               paddr = table_daddrs[tpidx] +
> +                                       (ETR_SG_PAGE_SIZE * (sgtidx + 1));
> +                       }
> +                       type = ETR_SG_ET_LINK;
> +               } else {
> +                       /*
> +                        * Update the idices to the data_pages to point to the
> +                        * next sg_page in the data buffer.
> +                        */
> +                       type = ETR_SG_ET_NORMAL;
> +                       paddr = data_daddrs[dpidx] + spidx * ETR_SG_PAGE_SIZE;
> +                       if (!INC_IDX_ROUND(spidx, ETR_SG_PAGES_PER_SYSPAGE))
> +                               dpidx++;
> +               }
> +               *ptr++ = ETR_SG_ENTRY(paddr, type);
> +               /*
> +                * Move to the next table pointer, moving the table page index
> +                * if necessary
> +                */
> +               if (!INC_IDX_ROUND(sgtoffset, ETR_SG_PTRS_PER_PAGE)) {
> +                       if (!INC_IDX_ROUND(sgtidx, ETR_SG_PAGES_PER_SYSPAGE))
> +                               tpidx++;
> +               }
> +       }
> +
> +       /* Set up the last entry, which is always a data pointer */
> +       paddr = data_daddrs[dpidx] + spidx * ETR_SG_PAGE_SIZE;
> +       *ptr++ = ETR_SG_ENTRY(paddr, ETR_SG_ET_LAST);
> +}
> +
> +/*
> + * tmc_init_etr_sg_table: Allocate a TMC ETR SG table, data buffer of @size and
> + * populate the table.
> + *
> + * @dev                - Device pointer for the TMC
> + * @node       - NUMA node where the memory should be allocated
> + * @size       - Total size of the data buffer
> + * @pages      - Optional list of page virtual address
> + */
> +static struct etr_sg_table __maybe_unused *
> +tmc_init_etr_sg_table(struct device *dev, int node,
> +                 unsigned long size, void **pages)
> +{
> +       int nr_entries, nr_tpages;
> +       int nr_dpages = size >> PAGE_SHIFT;
> +       struct tmc_sg_table *sg_table;
> +       struct etr_sg_table *etr_table;
> +
> +       etr_table = kzalloc(sizeof(*etr_table), GFP_KERNEL);
> +       if (!etr_table)
> +               return ERR_PTR(-ENOMEM);
> +       nr_entries = tmc_etr_sg_table_entries(nr_dpages);
> +       nr_tpages = DIV_ROUND_UP(nr_entries, ETR_SG_PTRS_PER_SYSPAGE);
> +
> +       sg_table = tmc_alloc_sg_table(dev, node, nr_tpages, nr_dpages, pages);
> +       if (IS_ERR(sg_table)) {
> +               kfree(etr_table);
> +               return ERR_PTR(PTR_ERR(sg_table));
> +       }
> +
> +       etr_table->sg_table = sg_table;
> +       /* TMC should use table base address for DBA */
> +       etr_table->hwaddr = sg_table->table_daddr;
> +       tmc_etr_sg_table_populate(etr_table);
> +       /* Sync the table pages for the HW */
> +       tmc_sg_table_sync_table(sg_table);
> +#ifdef ETR_SG_DEBUG
> +       tmc_etr_sg_table_dump(etr_table);
> +#endif
> +       return etr_table;
> +}
> +
>  static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata)
>  {
>         u32 axictl, sts;
> --
> 2.13.6
>