Re: [PATCH v4 7/8] netdev: octeon-ethernet: Add Cavium Octeon III support.

[David Daney <ddaney@caviumnetworks.com>]

On 11/29/2017 08:07 AM, Souptick Joarder wrote:
> On Wed, Nov 29, 2017 at 4:00 PM, Souptick Joarder <jrdr.linux@gmail.com> wrote:
>> On Wed, Nov 29, 2017 at 6:25 AM, David Daney <david.daney@cavium.com> wrote:
>>> From: Carlos Munoz <cmunoz@cavium.com>
>>>
>>> The Cavium OCTEON cn78xx and cn73xx SoCs have network packet I/O
>>> hardware that is significantly different from previous generations of
>>> the family.
> 
>>> diff --git a/drivers/net/ethernet/cavium/octeon/octeon3-bgx-port.c b/drivers/net/ethernet/cavium/octeon/octeon3-bgx-port.c
>>> new file mode 100644
>>> index 000000000000..4dad35fa4270
>>> --- /dev/null
>>> +++ b/drivers/net/ethernet/cavium/octeon/octeon3-bgx-port.c
>>> @@ -0,0 +1,2033 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/* Copyright (c) 2017 Cavium, Inc.
>>> + *
>>> + * This file is subject to the terms and conditions of the GNU General Public
>>> + * License.  See the file "COPYING" in the main directory of this archive
>>> + * for more details.
>>> + */
>>> +#include <linux/platform_device.h>
>>> +#include <linux/netdevice.h>
>>> +#include <linux/etherdevice.h>
>>> +#include <linux/of_platform.h>
>>> +#include <linux/of_address.h>
>>> +#include <linux/of_mdio.h>
>>> +#include <linux/of_net.h>
>>> +#include <linux/module.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/list.h>
>>> +
> 
>>> +static void bgx_port_sgmii_set_link_down(struct bgx_port_priv *priv)
>>> +{
>>> +       u64     data;
> 
>>> +       data = oct_csr_read(BGX_GMP_PCS_MISC_CTL(priv->node, priv->bgx, priv->index));
>>> +       data |= BIT(11);
>>> +       oct_csr_write(data, BGX_GMP_PCS_MISC_CTL(priv->node, priv->bgx, priv->index));
>>> +       data = oct_csr_read(BGX_GMP_PCS_MISC_CTL(priv->node, priv->bgx, priv->index));
>>
>> Any particular reason to read immediately after write ?
> 

Yes, to ensure the write is committed to hardware before the next step.

> 
> 
>>> +static int bgx_port_sgmii_set_link_speed(struct bgx_port_priv *priv, struct port_status status)
>>> +{
>>> +       u64     data;
>>> +       u64     prtx;
>>> +       u64     miscx;
>>> +       int     timeout;
>>> +
> 
>>> +
>>> +       switch (status.speed) {
>>> +       case 10:
>>
>> In my opinion, instead of hard coding the value, is it fine to use ENUM ?
>     Similar comments applicable in other places where hard coded values are used.
> 

There is nothing to be gained by interposing an extra layer of 
abstraction in this case.  The code is more clear with the raw numbers 
in this particular case.


> 
> 
>>> +static int bgx_port_gser_27882(struct bgx_port_priv *priv)
>>> +{
>>> +       u64     data;
>>> +       u64     addr;
>>
>>> +       int     timeout = 200;
>>> +
>>> +   //    timeout = 200;
> Better to initialize the timeout value

What are you talking about?  It is properly initialized using valid C code.


> 
> 
>>> +static int bgx_port_qlm_rx_equalization(struct bgx_port_priv *priv, int qlm, int lane)
>>> +{
>>> +       lmode = oct_csr_read(GSER_LANE_MODE(priv->node, qlm));
>>> +       lmode &= 0xf;
>>> +       addr = GSER_LANE_P_MODE_1(priv->node, qlm, lmode);
>>> +       data = oct_csr_read(addr);
>>> +       /* Don't complete rx equalization if in VMA manual mode */
>>> +       if (data & BIT(14))
>>> +               return 0;
>>> +
>>> +       /* Apply rx equalization for speed > 6250 */
>>> +       if (bgx_port_get_qlm_speed(priv, qlm) < 6250)
>>> +               return 0;
>>> +
>>> +       /* Wait until rx data is valid (CDRLOCK) */
>>> +       timeout = 500;
>>
>> 500 us is the min required value or it can be further reduced ?
> 


500 uS works well and is shorter than the 2000 uS from the hardware manual.

If you would like to verify shorter timeout values, we could consider 
merging such a patch.  But really, this doesn't matter as it is a very 
short one-off action when the link is brought up.

> 
>>> +static int bgx_port_init_xaui_link(struct bgx_port_priv *priv)
>>> +{
> 
>>> +
>>> +               if (use_ber) {
>>> +                       timeout = 10000;
>>> +                       do {
>>> +                               data =
>>> +                               oct_csr_read(BGX_SPU_BR_STATUS1(priv->node, priv->bgx, priv->index));
>>> +                               if (data & BIT(0))
>>> +                                       break;
>>> +                               timeout--;
>>> +                               udelay(1);
>>> +                       } while (timeout);
>>
>> In my opinion, it's better to implement similar kind of loops inside macros.

Ok, duly noted.  I think we are in disagreement with respect to this point.

>>
>>> +                       if (!timeout) {
>>> +                               pr_debug("BGX%d:%d:%d: BLK_LOCK timeout\n",
>>> +                                        priv->bgx, priv->index, priv->node);
>>> +                               return -1;
>>> +                       }
>>> +               } else {
>>> +                       timeout = 10000;
>>> +                       do {
>>> +                               data =
>>> +                               oct_csr_read(BGX_SPU_BX_STATUS(priv->node, priv->bgx, priv->index));
>>> +                               if (data & BIT(12))
>>> +                                       break;
>>> +                               timeout--;
>>> +                               udelay(1);
>>> +                       } while (timeout);
>> same here