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Message-ID: <20171103222200.GA13173@xps15>
Date: Fri, 3 Nov 2017 16:22:00 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
rob.walker@....com, mike.leach@...aro.org,
coresight@...ts.linaro.org
Subject: Re: [PATCH 14/17] coresight: etr: Add support for save restore
buffers
On Thu, Oct 19, 2017 at 06:15:50PM +0100, Suzuki K Poulose wrote:
> Add support for creating buffers which can be used in save-restore
> mode (e.g, for use by perf). If the TMC-ETR supports save-restore
> feature, we could support the mode in all buffer backends. However,
Instead of using the term backend simply write continuous buffer or SG mode. It
is a lot less cryptic that way.
> if it doesn't, we should fall back to using in built SG mechanism,
> where we can rotate the SG table by making some adjustments in the
> page table.
>
> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 132 +++++++++++++++++++++++-
> drivers/hwtracing/coresight/coresight-tmc.h | 15 +++
> 2 files changed, 143 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 849684f85443..f8e654e1f5b2 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -590,7 +590,7 @@ tmc_etr_sg_table_index_to_daddr(struct tmc_sg_table *sg_table, u32 index)
> * 3) Update the hwaddr to point to the table pointer for the buffer
> * which starts at "base".
> */
> -static int __maybe_unused
> +static int
> tmc_etr_sg_table_rotate(struct etr_sg_table *etr_table, u64 base_offset)
> {
> u32 last_entry, first_entry;
> @@ -700,6 +700,9 @@ static int tmc_etr_alloc_flat_buf(struct tmc_drvdata *drvdata,
> return -ENOMEM;
> etr_buf->vaddr = vaddr;
> etr_buf->hwaddr = paddr;
> + etr_buf->rrp = paddr;
> + etr_buf->rwp = paddr;
> + etr_buf->status = 0;
> etr_buf->mode = ETR_MODE_FLAT;
> etr_buf->private = drvdata;
> return 0;
> @@ -754,13 +757,19 @@ static int tmc_etr_alloc_sg_buf(struct tmc_drvdata *drvdata,
> void **pages)
> {
> struct etr_sg_table *etr_table;
> + struct tmc_sg_table *sg_table;
>
> etr_table = tmc_init_etr_sg_table(drvdata->dev, node,
> etr_buf->size, pages);
> if (IS_ERR(etr_table))
> return -ENOMEM;
> + sg_table = etr_table->sg_table;
As far as I can tell this doesn't do anything.
> etr_buf->vaddr = tmc_sg_table_data_vaddr(etr_table->sg_table);
> etr_buf->hwaddr = etr_table->hwaddr;
> + /* TMC ETR SG automatically sets the RRP/RWP when enabled */
If TMC ETR SG automatically sets the RRP/RWP, why explicitly setting it?
> + etr_buf->rrp = etr_table->hwaddr;
> + etr_buf->rwp = etr_table->hwaddr;
> + etr_buf->status = 0;
> etr_buf->mode = ETR_MODE_ETR_SG;
> etr_buf->private = etr_table;
> return 0;
> @@ -816,11 +825,49 @@ static void tmc_etr_sync_sg_buf(struct etr_buf *etr_buf, u64 rrp, u64 rwp)
> tmc_sg_table_sync_data_range(table, r_offset, etr_buf->len);
> }
>
> +static int tmc_etr_restore_sg_buf(struct etr_buf *etr_buf,
> + u64 r_offset, u64 w_offset,
> + u32 status, bool has_save_restore)
Indentation
> +{
> + int rc;
> + struct etr_sg_table *etr_table = etr_buf->private;
> + struct device *dev = etr_table->sg_table->dev;
> +
> + /*
> + * It is highly unlikely that we have an ETR with in-built SG and
> + * Save-Restore capability and we are not sure if the PTRs will
> + * be updated.
> + */
> + if (has_save_restore) {
> + dev_warn_once(dev,
> + "Unexpected feature combination of SG and save-restore\n");
> + return -EINVAL;
> + }
> +
> + /*
> + * Since we cannot program RRP/RWP different from DBAL, the offsets
> + * should match.
> + */
> + if (r_offset != w_offset) {
> + dev_dbg(dev, "Mismatched RRP/RWP offsets\n");
> + return -EINVAL;
> + }
> +
> + rc = tmc_etr_sg_table_rotate(etr_table, w_offset);
> + if (!rc) {
> + etr_buf->hwaddr = etr_table->hwaddr;
> + etr_buf->rrp = etr_table->hwaddr;
> + etr_buf->rwp = etr_table->hwaddr;
> + }
> + return rc;
> +}
> +
> static const struct etr_buf_operations etr_sg_buf_ops = {
> .alloc = tmc_etr_alloc_sg_buf,
> .free = tmc_etr_free_sg_buf,
> .sync = tmc_etr_sync_sg_buf,
> .get_data = tmc_etr_get_data_sg_buf,
> + .restore = tmc_etr_restore_sg_buf,
> };
>
> static const struct etr_buf_operations *etr_buf_ops[] = {
> @@ -861,10 +908,42 @@ static struct etr_buf *tmc_alloc_etr_buf(struct tmc_drvdata *drvdata,
> {
> int rc = -ENOMEM;
> bool has_etr_sg, has_iommu;
> + bool has_flat, has_save_restore;
> struct etr_buf *etr_buf;
>
> has_etr_sg = tmc_etr_has_cap(drvdata, TMC_ETR_SG);
> has_iommu = iommu_get_domain_for_dev(drvdata->dev);
> + has_save_restore = tmc_etr_has_cap(drvdata, TMC_ETR_SAVE_RESTORE);
> +
> + /*
> + * We can normally use flat DMA buffer provided that the buffer
> + * is not used in save restore fashion without hardware support.
> + */
> + has_flat = !(flags & ETR_BUF_F_RESTORE_PTRS) || has_save_restore;
> +
> + /*
> + * To support save-restore on a given ETR we have the following
> + * conditions:
> + * 1) If the buffer requires save-restore of a pointers as well
> + * as the Status bit, we require ETR support for it and we coul
> + * support all the backends.
> + * 2) If the buffer requires only save-restore of pointers, then
> + * we could exploit a circular ETR SG list. None of the other
> + * backends can support it without the ETR feature.
> + *
> + * If the buffer will be used in a save-restore mode without
> + * the ETR support for SAVE_RESTORE, we can only support TMC
> + * ETR in-built SG tables which can be rotated to make it work.
> + */
> + if ((flags & ETR_BUF_F_RESTORE_STATUS) && !has_save_restore)
> + return ERR_PTR(-EINVAL);
> +
> + if (!has_flat && !has_etr_sg) {
> + dev_dbg(drvdata->dev,
> + "No available backends for ETR buffer with flags %x\n",
> + flags);
> + return ERR_PTR(-EINVAL);
> + }
>
> etr_buf = kzalloc(sizeof(*etr_buf), GFP_KERNEL);
> if (!etr_buf)
> @@ -883,7 +962,7 @@ static struct etr_buf *tmc_alloc_etr_buf(struct tmc_drvdata *drvdata,
> * Fallback to available mechanisms.
> *
> */
> - if (!pages &&
> + if (!pages && has_flat &&
> (!has_etr_sg || has_iommu || size < SZ_1M))
> rc = tmc_etr_mode_alloc_buf(ETR_MODE_FLAT, drvdata,
> etr_buf, node, pages);
> @@ -961,6 +1040,51 @@ static void tmc_sync_etr_buf(struct tmc_drvdata *drvdata)
> tmc_etr_buf_insert_barrier_packet(etr_buf, etr_buf->offset);
> }
>
> +/*
> + * tmc_etr_restore_generic: Common helper to restore the buffer
> + * status for FLAT buffers, which use linear TMC ETR address range.
> + * This is only possible with in-built ETR capability to save-restore
> + * the pointers. The DBA will still point to the original start of the
> + * buffer.
> + */
> +static int tmc_etr_buf_generic_restore(struct etr_buf *etr_buf,
> + u64 r_offset, u64 w_offset,
> + u32 status, bool has_save_restore)
Indentation
> +{
> + u64 size = etr_buf->size;
> +
> + if (!has_save_restore)
> + return -EINVAL;
> + etr_buf->rrp = etr_buf->hwaddr + (r_offset % size);
> + etr_buf->rwp = etr_buf->hwaddr + (w_offset % size);
> + etr_buf->status = status;
> + return 0;
> +}
> +
> +static int __maybe_unused
> +tmc_restore_etr_buf(struct tmc_drvdata *drvdata, struct etr_buf *etr_buf,
> + u64 r_offset, u64 w_offset, u32 status)
> +{
> + bool has_save_restore = tmc_etr_has_cap(drvdata, TMC_ETR_SAVE_RESTORE);
> +
> + if (WARN_ON_ONCE(!has_save_restore && etr_buf->mode != ETR_MODE_ETR_SG))
> + return -EINVAL;
> + /*
> + * If we use a circular SG list without ETR support, we can't
> + * support restoring "Full" bit.
> + */
> + if (WARN_ON_ONCE(!has_save_restore && status))
> + return -EINVAL;
> + if (status & ~TMC_STS_FULL)
> + return -EINVAL;
> + if (etr_buf->ops->restore)
> + return etr_buf->ops->restore(etr_buf, r_offset, w_offset,
> + status, has_save_restore);
> + else
> + return tmc_etr_buf_generic_restore(etr_buf, r_offset, w_offset,
> + status, has_save_restore);
> +}
> +
> static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata,
> struct etr_buf *etr_buf)
> {
> @@ -1004,8 +1128,8 @@ static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata,
> * STS to "not full").
> */
> if (tmc_etr_has_cap(drvdata, TMC_ETR_SAVE_RESTORE)) {
> - tmc_write_rrp(drvdata, etr_buf->hwaddr);
> - tmc_write_rwp(drvdata, etr_buf->hwaddr);
> + tmc_write_rrp(drvdata, etr_buf->rrp);
> + tmc_write_rwp(drvdata, etr_buf->rwp);
> sts = readl_relaxed(drvdata->base + TMC_STS) & ~TMC_STS_FULL;
> writel_relaxed(sts, drvdata->base + TMC_STS);
> }
> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
> index 14a3dec50b0f..2c5b905b6494 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc.h
> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
> @@ -142,12 +142,22 @@ enum etr_mode {
> ETR_MODE_ETR_SG, /* Uses in-built TMC ETR SG mechanism */
> };
>
> +/* ETR buffer should support save-restore */
> +#define ETR_BUF_F_RESTORE_PTRS 0x1
> +#define ETR_BUF_F_RESTORE_STATUS 0x2
> +
> +#define ETR_BUF_F_RESTORE_MINIMAL ETR_BUF_F_RESTORE_PTRS
> +#define ETR_BUF_F_RESTORE_FULL (ETR_BUF_F_RESTORE_PTRS |\
> + ETR_BUF_F_RESTORE_STATUS)
> struct etr_buf_operations;
>
> /**
> * struct etr_buf - Details of the buffer used by ETR
> * @mode : Mode of the ETR buffer, contiguous, Scatter Gather etc.
> * @full : Trace data overflow
> + * @status : Value for STATUS if the ETR supports save-restore.
> + * @rrp : Value for RRP{LO:HI} if the ETR supports save-restore
> + * @rwp : Value for RWP{LO:HI} if the ETR supports save-restore
> * @size : Size of the buffer.
> * @hwaddr : Address to be programmed in the TMC:DBA{LO,HI}
> * @vaddr : Virtual address of the buffer used for trace.
> @@ -159,6 +169,9 @@ struct etr_buf_operations;
> struct etr_buf {
> enum etr_mode mode;
> bool full;
> + u32 status;
> + dma_addr_t rrp;
> + dma_addr_t rwp;
> ssize_t size;
> dma_addr_t hwaddr;
> void *vaddr;
> @@ -212,6 +225,8 @@ struct etr_buf_operations {
> int (*alloc)(struct tmc_drvdata *drvdata, struct etr_buf *etr_buf,
> int node, void **pages);
> void (*sync)(struct etr_buf *etr_buf, u64 rrp, u64 rwp);
> + int (*restore)(struct etr_buf *etr_buf, u64 r_offset,
> + u64 w_offset, u32 status, bool has_save_restore);
> ssize_t (*get_data)(struct etr_buf *etr_buf, u64 offset, size_t len,
> char **bufpp);
> void (*free)(struct etr_buf *etr_buf);
> --
> 2.13.6
>
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