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Date: Fri, 31 Jul 2020 18:22:01 +0300
From: Vadym Kochan <vadym.kochan@...ision.eu>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Jiri Pirko <jiri@...lanox.com>,
Ido Schimmel <idosch@...lanox.com>,
Andrew Lunn <andrew@...n.ch>,
Oleksandr Mazur <oleksandr.mazur@...ision.eu>,
Serhiy Boiko <serhiy.boiko@...ision.eu>,
Serhiy Pshyk <serhiy.pshyk@...ision.eu>,
Volodymyr Mytnyk <volodymyr.mytnyk@...ision.eu>,
Taras Chornyi <taras.chornyi@...ision.eu>,
Andrii Savka <andrii.savka@...ision.eu>,
netdev <netdev@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Mickey Rachamim <mickeyr@...vell.com>
Subject: Re: [net-next v4 1/6] net: marvell: prestera: Add driver for
Prestera family ASIC devices
Hi Andy,
On Mon, Jul 27, 2020 at 03:59:13PM +0300, Andy Shevchenko wrote:
> On Mon, Jul 27, 2020 at 3:23 PM Vadym Kochan <vadym.kochan@...ision.eu> wrote:
> >
> > Marvell Prestera 98DX326x integrates up to 24 ports of 1GbE with 8
> > ports of 10GbE uplinks or 2 ports of 40Gbps stacking for a largely
> > wireless SMB deployment.
> >
> > The current implementation supports only boards designed for the Marvell
> > Switchdev solution and requires special firmware.
> >
> > The core Prestera switching logic is implemented in prestera_main.c,
> > there is an intermediate hw layer between core logic and firmware. It is
> > implemented in prestera_hw.c, the purpose of it is to encapsulate hw
> > related logic, in future there is a plan to support more devices with
> > different HW related configurations.
> >
> > This patch contains only basic switch initialization and RX/TX support
> > over SDMA mechanism.
> >
> > Currently supported devices have DMA access range <= 32bit and require
> > ZONE_DMA to be enabled, for such cases SDMA driver checks if the skb
> > allocated in proper range supported by the Prestera device.
> >
> > Also meanwhile there is no TX interrupt support in current firmware
> > version so recycling work is scheduled on each xmit.
> >
> > Port's mac address is generated from the switch base mac which may be
> > provided via device-tree (static one or as nvme cell), or randomly
> > generated.
>
> ...
>
> > Signed-off-by: Andrii Savka <andrii.savka@...ision.eu>
> > Signed-off-by: Oleksandr Mazur <oleksandr.mazur@...ision.eu>
> > Signed-off-by: Serhiy Boiko <serhiy.boiko@...ision.eu>
> > Signed-off-by: Serhiy Pshyk <serhiy.pshyk@...ision.eu>
> > Signed-off-by: Taras Chornyi <taras.chornyi@...ision.eu>
> > Signed-off-by: Volodymyr Mytnyk <volodymyr.mytnyk@...ision.eu>
> > Signed-off-by: Vadym Kochan <vadym.kochan@...ision.eu>
>
> This needs more work. You have to really understand the role of each
> person in the above list.
> I highly recommend (re-)read sections 11-13 of Submitting Patches.
>
At least looks like I need to add these persons as Co-author's.
> ...
>
> > +/* SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
>
> The idea of SPDX is to have it as a separate (standalone) comment.
OK, thanks.
>
> ...
>
> > +enum prestera_event_type {
> > + PRESTERA_EVENT_TYPE_UNSPEC,
> > +
> > + PRESTERA_EVENT_TYPE_PORT,
> > + PRESTERA_EVENT_TYPE_RXTX,
> > +
> > + PRESTERA_EVENT_TYPE_MAX,
>
> Commas in the terminators are not good.
>
OK
> > +};
>
> ...
>
> > +#include "prestera_dsa.h"
>
> The idea that you include more generic headers earlier than more custom ones.
>
Thanks
> > +#include <linux/string.h>
> > +#include <linux/bitops.h>
> > +#include <linux/bitfield.h>
> > +#include <linux/errno.h>
>
> Perhaps ordered?
>
alphabetical ?
> ...
>
> > +/* TrgDev[4:0] = {Word0[28:24]} */
>
> > + * SrcPort/TrgPort[7:0] = {Word2[20], Word1[11:10], Word0[23:19]}
>
> > +/* bits 13:15 -- UP */
>
> > +/* bits 0:11 -- VID */
>
> These are examples of useless comments.
>
OK, removed.
> ...
>
> > + dsa->vlan.is_tagged = (bool)FIELD_GET(PRESTERA_W0_IS_TAGGED, words[0]);
> > + dsa->vlan.cfi_bit = (u8)FIELD_GET(PRESTERA_W1_CFI_BIT, words[1]);
> > + dsa->vlan.vpt = (u8)FIELD_GET(PRESTERA_W0_VPT, words[0]);
> > + dsa->vlan.vid = (u16)FIELD_GET(PRESTERA_W0_VID, words[0]);
>
> Do you need those castings?
>
Looks like not, because the struct fields are same type as cast'ed ones.
> ...
>
> > + struct prestera_msg_event_port *hw_evt;
> > +
> > + hw_evt = (struct prestera_msg_event_port *)msg;
>
> Can be one line I suppose.
>
Yes, but I am trying to avoid line-breaking because of 80 chars
limitation.
> ...
>
> > + if (evt->id == PRESTERA_PORT_EVENT_STATE_CHANGED)
> > + evt->port_evt.data.oper_state = hw_evt->param.oper_state;
> > + else
> > + return -EINVAL;
> > +
> > + return 0;
>
> Perhaps traditional pattern, i.e.
>
> if (...)
> return -EINVAL;
> ...
> return 0;
>
I am not sure if it is applicable here, because the error state here
is if 'evt->id' did not matched after all checks. Actually this is
simply a 'switch', but I use 'if' to have shorter code.
> ...
>
> > + err = fw_event_parsers[msg->type].func(buf, &evt);
> > + if (!err)
> > + eh.func(sw, &evt, eh.arg);
>
> Ditto.
Makes sense.
>
> > + return err;
>
> ...
>
> > + memcpy(&req.param.mac, mac, sizeof(req.param.mac));
>
> Consider to use ether_addr_*() APIs instead of open-coded mem*() ones.
>
> ...
>
> > +#define PRESTERA_MTU_DEFAULT 1536
>
> Don't we have global default for this?
>
> ...
>
> > +#define PRESTERA_STATS_DELAY_MS msecs_to_jiffies(1000)
>
> It's not _MS.
>
> ...
>
> > + if (!is_up)
> > + netif_stop_queue(dev);
> > +
> > + err = prestera_hw_port_state_set(port, is_up);
> > +
> > + if (is_up && !err)
> > + netif_start_queue(dev);
>
> Much better if will look lke
>
> if (is_up) {
> ...
> err = ...(..., true);
> if (err)
> return err;
> ...
> } else {
> return prestera_*(..., false);
> }
> return 0;
>
> > + return err;
>
> ...
>
> > + /* Only 0xFF mac addrs are supported */
> > + if (port->fp_id >= 0xFF)
> > + goto err_port_init;
>
> You meant 255, right?
> Otherwise you have to mentioned is it byte limitation or what?
>
> ...
Yes, 255 is a limitation because of max byte value.
>
> > +static int prestera_switch_set_base_mac_addr(struct prestera_switch *sw)
> > +{
> > + struct device_node *base_mac_np;
> > + struct device_node *np;
>
> > + np = of_find_compatible_node(NULL, NULL, "marvell,prestera");
> > + if (np) {
> > + base_mac_np = of_parse_phandle(np, "base-mac-provider", 0);
> > + if (base_mac_np) {
> > + const char *base_mac;
> > +
> > + base_mac = of_get_mac_address(base_mac_np);
> > + of_node_put(base_mac_np);
> > + if (!IS_ERR(base_mac))
> > + ether_addr_copy(sw->base_mac, base_mac);
> > + }
> > + }
> > +
> > + if (!is_valid_ether_addr(sw->base_mac)) {
> > + eth_random_addr(sw->base_mac);
> > + dev_info(sw->dev->dev, "using random base mac address\n");
> > + }
>
> Isn't it device_get_mac_address() reimplementation?
>
device_get_mac_address() just tries to get mac via fwnode.
> > +
> > + return prestera_hw_switch_mac_set(sw, sw->base_mac);
> > +}
>
> ...
>
> > + err = prestera_switch_init(sw);
> > + if (err) {
> > + kfree(sw);
> > + return err;
> > + }
> > +
> > + return 0;
>
> if (err)
> kfree(...);
> return err;
>
> Also, check reference counting.
>
> ...
>
> > +#define PRESTERA_SDMA_RX_DESC_PKT_LEN(desc) \
>
> > + ((le32_to_cpu((desc)->word2) >> 16) & 0x3FFF)
>
> Why not GENMASK() ?
Yes, GENMASK is right way to go, thanks.
>
> ...
>
> > + if (dma + sizeof(struct prestera_sdma_desc) > sdma->dma_mask) {
> > + dev_err(dma_dev, "failed to alloc desc\n");
> > + dma_pool_free(sdma->desc_pool, desc, dma);
>
> Better first undo something *then* print a message.
>
> > + return -ENOMEM;
> > + }
>
> ...
>
> > +static void prestera_sdma_rx_desc_set_len(struct prestera_sdma_desc *desc,
> > + size_t val)
> > +{
> > + u32 word = le32_to_cpu(desc->word2);
> > +
> > + word = (word & ~GENMASK(15, 0)) | val;
>
> Shouldn't you do traditional pattern?
>
> word = (word & ~mask) | (val & mask);
Looks like this is safer form.
>
> > + desc->word2 = cpu_to_le32(word);
> > +}
>
> ...
>
> > + dma = dma_map_single(dev, skb->data, skb->len, DMA_FROM_DEVICE);
>
> > +
>
> Redundant blank line.
>
> > + if (dma_mapping_error(dev, dma))
> > + goto err_dma_map;
>
> ...
>
> > + pr_warn_ratelimited("received pkt for non-existent port(%u, %u)\n",
> > + dev_id, hw_port);
>
> netdev_warn_ratelimited() ? Or something closer to that?
>
> ...
>
> > + qmask = GENMASK(qnum - 1, 0);
>
> BIT(qnum) - 1 will produce much better code I suppose.
>
> ...
>
> > + if (pkts_done < budget && napi_complete_done(napi, pkts_done))
> > + prestera_write(sdma->sw, PRESTERA_SDMA_RX_INTR_MASK_REG,
> > + 0xff << 2);
>
> GENMASK() ?
>
> ...
>
> > + word = (word & ~GENMASK(30, 16)) | ((len + ETH_FCS_LEN) << 16);
>
> Consider traditional pattern.
>
> ...
>
> > + word |= PRESTERA_SDMA_TX_DESC_DMA_OWN << 31;
>
> I hope that was defined with U. Otherwise it's UB.
>
> ...
>
> > + new_skb = alloc_skb(len, GFP_ATOMIC | GFP_DMA);
>
> Atomic? Why?
>
TX path might be called from net_tx_action which is softirq.
> ...
>
> > +static int prestera_sdma_tx_wait(struct prestera_sdma *sdma,
> > + struct prestera_tx_ring *tx_ring)
> > +{
>
> > + int tx_retry_num = 10 * tx_ring->max_burst;
>
> Magic!
You mean the code is magic ? Yes, I am trying to relax the
calling of SDMA engine.
>
> > + while (--tx_retry_num) {
> > + if (prestera_sdma_is_ready(sdma))
> > + return 0;
> > +
> > + udelay(1);
> > + }
>
> unsigned int counter = ...;
>
> do { } while (--counter);
>
> looks better.
>
> Also, why udelay()? Is it atomic context?
TX path might be called from net_tx_action which is softirq.
>
> > + return -EBUSY;
> > +}
>
> ...
>
> > + if (!tx_ring->burst--) {
>
> Don't do like this. It makes code harder to understand.
>
> if (tx_ring->...) {
> ...->burst--;
> } else {
> ...
> }
I will try.
>
> > + tx_ring->burst = tx_ring->max_burst;
> > +
> > + err = prestera_sdma_tx_wait(sdma, tx_ring);
> > + if (err)
> > + goto drop_skb_unmap;
> > + }
>
> --
> With Best Regards,
> Andy Shevchenko
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