From: Logan Gunthorpe
> Seeing there is no dedicated hardware for this, we simply add
> these as entries in the shared memory window. Thus, we could support
> any number of them but 128 seems like enough, for now.
Scratchpads are not natively supported by this hardware,
- but the hardware does natively support more than two ntb ports,
- but this software substitute for scratchpads looks like it only works with two ntb ports:
> + if (pidx != NTB_DEF_PEER_IDX)
> + return -EINVAL;
This could get in the way of letting the driver support more than two ports later on. Is there already a plan to change this to support more than two ports?
This is also not the only hardware to lack scratchpads, but does have memory windows. Wouldn't it be better for a software substitute like this to be done in a way that it is not tied to a specific hardware driver?
>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Reviewed-by: Stephen Bates <sbates@xxxxxxxxxxxx>
> Reviewed-by: Kurt Schwemmer <kurt.schwemmer@xxxxxxxxxxxxx>
> ---
> drivers/ntb/hw/mscc/switchtec_ntb.c | 75 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 73 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/ntb/hw/mscc/switchtec_ntb.c b/drivers/ntb/hw/mscc/switchtec_ntb.c
> index 980acf2e5b42..a42e80742b52 100644
> --- a/drivers/ntb/hw/mscc/switchtec_ntb.c
> +++ b/drivers/ntb/hw/mscc/switchtec_ntb.c
> @@ -69,6 +69,7 @@ struct shared_mw {
> u16 nr_direct_mw;
> u16 nr_lut_mw;
> u64 mw_sizes[MAX_MWS];
> + u32 spad[128];
> };
>
> #define MAX_DIRECT_MW ARRAY_SIZE(((struct ntb_ctrl_regs *)(0))->bar_entry)
> @@ -453,22 +454,90 @@ static int switchtec_ntb_peer_db_set(struct ntb_dev *ntb, u64 db_bits)
>
> static int switchtec_ntb_spad_count(struct ntb_dev *ntb)
> {
> - return 0;
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> +
> + return ARRAY_SIZE(sndev->self_shared->spad);
> }
>
> static u32 switchtec_ntb_spad_read(struct ntb_dev *ntb, int idx)
> {
> - return 0;
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> +
> + if (idx < 0 || idx >= ARRAY_SIZE(sndev->self_shared->spad))
> + return 0;
> +
> + if (!sndev->self_shared)
> + return 0;
> +
> + return sndev->self_shared->spad[idx];
> }
>
> static int switchtec_ntb_spad_write(struct ntb_dev *ntb, int idx, u32 val)
> {
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> +
> + if (idx < 0 || idx >= ARRAY_SIZE(sndev->self_shared->spad))
> + return -EINVAL;
> +
> + if (!sndev->self_shared)
> + return -EIO;
> +
> + sndev->self_shared->spad[idx] = val;
> +
> return 0;
> }
>
> +static u32 switchtec_ntb_peer_spad_read(struct ntb_dev *ntb, int pidx,
> + int sidx)
> +{
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> +
> + if (pidx != NTB_DEF_PEER_IDX)
> + return -EINVAL;
> +
> + if (sidx < 0 || sidx >= ARRAY_SIZE(sndev->peer_shared->spad))
> + return 0;
> +
> + if (!sndev->peer_shared)
> + return 0;
> +
> + return ioread32(&sndev->peer_shared->spad[sidx]);
> +}
> +
> static int switchtec_ntb_peer_spad_write(struct ntb_dev *ntb, int pidx,
> int sidx, u32 val)
> {
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> +
> + if (pidx != NTB_DEF_PEER_IDX)
> + return -EINVAL;
> +
> + if (sidx < 0 || sidx >= ARRAY_SIZE(sndev->peer_shared->spad))
> + return -EINVAL;
> +
> + if (!sndev->peer_shared)
> + return -EIO;
> +
> + iowrite32(val, &sndev->peer_shared->spad[sidx]);
> +
> + return 0;
> +}
> +
> +static int switchtec_ntb_peer_spad_addr(struct ntb_dev *ntb, int pidx,
> + int sidx, phys_addr_t *spad_addr)
> +{
> + struct switchtec_ntb *sndev = ntb_sndev(ntb);
> + unsigned long offset;
> +
> + if (pidx != NTB_DEF_PEER_IDX)
> + return -EINVAL;
> +
> + offset = (unsigned long)&sndev->peer_shared->spad[sidx] -
> + (unsigned long)sndev->stdev->mmio;
> +
> + if (spad_addr)
> + *spad_addr = pci_resource_start(ntb->pdev, 0) + offset;
> +
> return 0;
> }
>
> @@ -494,7 +563,9 @@ static const struct ntb_dev_ops switchtec_ntb_ops = {
> .spad_count = switchtec_ntb_spad_count,
> .spad_read = switchtec_ntb_spad_read,
> .spad_write = switchtec_ntb_spad_write,
> + .peer_spad_read = switchtec_ntb_peer_spad_read,
> .peer_spad_write = switchtec_ntb_peer_spad_write,
> + .peer_spad_addr = switchtec_ntb_peer_spad_addr,
> };
>
> static void switchtec_ntb_init_sndev(struct switchtec_ntb *sndev)
> --
> 2.11.0
