netdev - Re: [patch net-next 2/4] mlxsw: Add PCI bus implementation

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Date:	Fri, 24 Jul 2015 07:30:58 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Scott Feldman <sfeldma@...il.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>, idosch@...lanox.com,
	eladr@...lanox.com,
	"ogerlitz@...lanox.com" <ogerlitz@...lanox.com>,
	Roopa Prabhu <roopa@...ulusnetworks.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Thomas Graf <tgraf@...g.ch>, ast@...mgrid.com,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	john fastabend <john.fastabend@...il.com>,
	"simon.horman@...ronome.com" <simon.horman@...ronome.com>,
	John Linville <linville@...driver.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Shrijeet Mukherjee <shm@...ulusnetworks.com>,
	"nhorman@...driver.com" <nhorman@...driver.com>,
	Jiri Pirko <jiri@...lanox.com>
Subject: Re: [patch net-next 2/4] mlxsw: Add PCI bus implementation

Fri, Jul 24, 2015 at 06:52:16AM CEST, sfeldma@...il.com wrote:
>On Thu, Jul 23, 2015 at 8:43 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>> From: Jiri Pirko <jiri@...lanox.com>
>>
>> Add PCI bus implementation for Mellanox Technologies Switch ASICs. This
>> includes firmware initialization, async queues manipulation and command
>> interface implementation.
>>
>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
>> Signed-off-by: Elad Raz <eladr@...lanox.com>
>
>[cut]
>
>> +static int mlxsw_pci_skb_transmit(void *bus_priv, struct sk_buff *skb,
>> +                                 const struct mlxsw_tx_info *tx_info)
>> +{
>> +       struct mlxsw_pci *mlxsw_pci = bus_priv;
>> +       struct mlxsw_pci_queue *q;
>> +       struct mlxsw_pci_queue_elem_info *elem_info;
>> +       char *wqe;
>> +       int i;
>> +       int err;
>> +
>> +       if (skb_shinfo(skb)->nr_frags > MLXSW_PCI_WQE_SG_ENTRIES - 1)
>> +               return -EINVAL;
>
>Can you skb_linearize() here to try to continue?

Sure, I think we can do it. This would be good to have in rocker too.


>
>> +       q = mlxsw_pci_sdq_pick(mlxsw_pci, tx_info);
>> +       spin_lock_bh(&q->lock);
>> +       elem_info = mlxsw_pci_queue_elem_info_producer_get(q);
>> +       if (!elem_info) {
>> +               /* queue is full */
>> +               err = -EAGAIN;
>> +               goto unlock;
>> +       }
>> +       elem_info->u.sdq.skb = skb;
>> +
>> +       wqe = elem_info->elem;
>> +       mlxsw_pci_wqe_c_set(wqe, 1); /* always report completion */
>> +       mlxsw_pci_wqe_lp_set(wqe, !!tx_info->is_emad);
>> +       mlxsw_pci_wqe_type_set(wqe, MLXSW_PCI_WQE_TYPE_ETHERNET);
>> +
>> +       err = mlxsw_pci_wqe_frag_map(mlxsw_pci, wqe, 0, skb->data,
>> +                                    skb_headlen(skb), DMA_TO_DEVICE);
>> +       if (err)
>> +               goto unlock;
>> +
>> +       for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
>> +               const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
>> +
>> +               err = mlxsw_pci_wqe_frag_map(mlxsw_pci, wqe, i + 1,
>> +                                            skb_frag_address(frag),
>> +                                            skb_frag_size(frag),
>> +                                            DMA_TO_DEVICE);
>> +               if (err)
>> +                       goto unmap_frags;
>> +       }
>> +
>> +       /* Set unused sq entries byte count to zero. */
>> +       for (i++; i < MLXSW_PCI_WQE_SG_ENTRIES; i++)
>> +               mlxsw_pci_wqe_byte_count_set(wqe, i, 0);
>
>Is hw OK with not clearing the unused sq entries dma_address?  Setting
>byte_count to zero must be sufficient?

Yes, byte_count == 0 is sufficient. No need to set address.


>
>> +
>> +       /* Everything is set up, ring producer doorbell to get HW going */
>> +       q->producer_counter++;
>> +       mlxsw_pci_queue_doorbell_producer_ring(mlxsw_pci, q);
>> +
>> +       goto unlock;
>> +
>> +unmap_frags:
>> +       for (; i >= 0; i--)
>> +               mlxsw_pci_wqe_frag_unmap(mlxsw_pci, wqe, i, DMA_TO_DEVICE);
>> +unlock:
>> +       spin_unlock_bh(&q->lock);
>> +       return err;
>> +}
>> +
>> +static int mlxsw_pci_cmd_exec(void *bus_priv, u16 opcode, u8 opcode_mod,
>> +                             u32 in_mod, bool out_mbox_direct,
>> +                             char *in_mbox, size_t in_mbox_size,
>> +                             char *out_mbox, size_t out_mbox_size,
>> +                             u8 *p_status)
>> +{
>> +       struct mlxsw_pci *mlxsw_pci = bus_priv;
>> +       dma_addr_t in_mapaddr = 0;
>> +       dma_addr_t out_mapaddr = 0;
>> +       bool evreq = mlxsw_pci->cmd.nopoll;
>> +       unsigned long timeout = msecs_to_jiffies(MLXSW_PCI_CIR_TIMEOUT_MSECS);
>> +       bool *p_wait_done = &mlxsw_pci->cmd.wait_done;
>
>Why is this initialized and then later set to false?

*p_wait_done
so we actually set not p_wait_done but mlxsw_pci->cmd.wait_done there.
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