Re: [PATCH 04/10] net: stmmac: sunxi platfrom extensions for GMAC inAllwinner A20 SoC's

[Chen-Yu Tsai]

Hi,

On Mon, Dec 9, 2013 at 7:10 PM, srinivas kandagatla
<srinivas.kandagatla@xxxxxx> wrote:
> Hi Chen,
> Good to know that Allwinner uses gmac.

To my knowledge, Allwinner has never confirmed this.

> On ST SoC, we have very similar requirements, before we merge any of
> these changes I think we need to come up with common way to solve both
> Allwinner and ST SOCs use cases.
>
> I have already posted few patches on to net-dev
> http://lkml.org/lkml/2013/11/12/243 to add Glue driver on top of stmmac
> driver.
>
>
> There are few reasons for the way I have done it.
>
> 1> I did not want to modify gmac driver in any sense to when a new SOC
> support is added.

My approach would add one line (compatible strings) each time.

> 2> As the SOC specific glue logic sits on top of standard GMAC IP, it
> makes sense to represent it proper harware hierarchy.

My feeling is that the SoC specifics are not a glue layer around dwmac,
rather an interconnected extension. Arguably I do not have the whole
picture. Allwinner has refused to provide us with any specifics beyond
the SoC manual and drivers. As such I can only make educated guesses on
how the dwmac core interacts with the other modules.

> 3> Did not want to change any generic gmac bindings for SOC specific
> stuff as requirements if SOC glue would be very different in each case.

We could try to define a standard set of clocks and reset controllers.
The dwmac does not have much additional tunables in the driver.
Anything else should be SoC specific, put in an extension, and
documented as such.

> I see issues with this approach, which are addressed in my patches.
>
> Please have a look at the http://lkml.org/lkml/2013/11/12/462 patch on
> STi SOC glue, which does implement a very similar glue driver.
>
> Do you see any issues not to do that way?

The glue layer driver would not have access to any of dwmac driver's
internals, nor could it respond to any state changes.

For example, .fix_mac_speed is called whenever auto-negotiation happens,
or when the link goes down or up. Maybe some future SoC would need this.

The Allwinner A20 has the option to use the external 125MHz clock
provided by the PHY for the tx clock under RGMII mode, with multiple
dividers yielding 125, 25, or 2.5 MHz. It seems this would require
.fix_mac_speed, though I have not tested it. My goal was to produce
a usable driver, rather than test all the possibilities.

The other issue is when the glue layer needs to set SoC specific
implementation details of the dwmac, when it is not possible to
add a generic dwmac compatible. See next section for more on this.

> On 06/12/13 17:29, Chen-Yu Tsai wrote:
>> The Allwinner A20 has an ethernet controller that seems to be
>> an early version of Synopsys DesignWare MAC 10/100/1000 Universal,
>> which is supported by the stmmac driver.
>>
>> Allwinner's GMAC requires setting additional registers in the SoC's
>> clock control unit.
>>
>> The exact version of the DWMAC IP that Allwinner uses is unknown,
>> thus the exact feature set is unknown.
>>
>> Signed-off-by: Chen-Yu Tsai <wens@xxxxxxxx>
>> ---
>>  .../bindings/net/allwinner,sun7i-gmac.txt          | 22 +++++++
>>  drivers/net/ethernet/stmicro/stmmac/Kconfig        | 12 ++++
>>  drivers/net/ethernet/stmicro/stmmac/Makefile       |  1 +
>>  drivers/net/ethernet/stmicro/stmmac/dwmac-sunxi.c  | 76 ++++++++++++++++++++++
>>  drivers/net/ethernet/stmicro/stmmac/stmmac.h       |  3 +lot
>>  .../net/ethernet/stmicro/stmmac/stmmac_platform.c  |  3 +
>>  6 files changed, 117 insertions(+)
>> http://lkml.org/lkml/2013/11/12/462
>> diff --git a/Documentation/devicetree/bindings/net/allwinner,sun7i-gmac.txt b/Documentation/devicetree/bindings/net/allwinner,sun7i-gmac.txt
>
>> --- /dev/null
>> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-sunxi.c
>> @@ -0,0 +1,76 @@
>> +/**
>> + * dwmac-sunxi.c - Allwinner sunxi DWMAC specific glue layer
>> + *
>> + * Copyright (C) 2013 Chen-Yu Tsai
>> + *
>> + * Chen-Yu Tsai  <wens@xxxxxxxx>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License as published by
>> + * the Free Software Foundation; either version 2 of the License, orhttp://lkml.org/lkml/2013/11/12/462
>> + * (at your option) any later version.
>> + *http://lkml.org/lkml/2013/11/12/462
>> + * This program is distributed in the hope that it will be useful,http://lkml.org/lkml/2013/11/12/462
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/phy.h>
>> +#include <linux/stmmac.h>
>> +
>> +#define GMAC_IF_TYPE_RGMII   0x4
>> +
>> +#define GMAC_TX_CLK_MASK     0x3
>> +#define GMAC_TX_CLK_MII              0x0
>> +#define GMAC_TX_CLK_RGMII_INT        0x2
>> +
>> +static int sun7i_gmac_init(struct platform_device *pdev)
>> +{
>> +     struct resource *res;
>> +     struct device *dev = &pdev->dev;
>> +     void __iomem *addr = NULL;
>> +     struct plat_stmmacenet_data *plat_dat = NULL;
>> +     u32 priv_clk_reg;
>> +
>> +     plat_dat = dev_get_platdata(&pdev->dev);
> This is not valid for DT case.
> In DT case stmmac maintains its own instance of platform data.
>
> Setting platform data dynamically after probe to a device is not the
> right way to do.

I see. And stmmac's own instance of platform data is associated with the
device in stmmac_dvr_probe. To make this work, we would have to move
setting dev->priv->plat in front of the .init callback.

>> +     if (!plat_dat)
>> +             return -EINVAL;
>> +
>> +     /* Get GMAC clock register in CCU */
>> +     res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
>> +     addr = devm_ioremap_resource(dev, res);
>> +     if (IS_ERR(addr))
>> +             return PTR_ERR(addr);
>> +
>> +     priv_clk_reg = readl(addr);
>> +
>> +     /* Set GMAC interface port mode */
>> +     if (plat_dat->interface == PHY_INTERFACE_MODE_RGMII)
>> +             priv_clk_reg |= GMAC_IF_TYPE_RGMII;
>> +     else
>> +             priv_clk_reg &= ~GMAC_IF_TYPE_RGMII;
>> +
>> +     /* Set GMAC transmit clock source. */
>> +     priv_clk_reg &= ~GMAC_TX_CLK_MASK;
>> +     if (plat_dat->interface == PHY_INTERFACE_MODE_RGMII
>> +                     || plat_dat->interface == PHY_INTERFACE_MODE_GMII)
>> +             priv_clk_reg |= GMAC_TX_CLK_RGMII_INT;
>> +     else
>> +             priv_clk_reg |= GMAC_TX_CLK_MII;
>> +
>> +     writel(priv_clk_reg, addr);
>> +
>> +     /* mask out phy addr 0x0 */
>> +     plat_dat->mdio_bus_data->phy_mask = 0x1;
>> +per
>> +     return 0;
>> +}
>> +
> This routine would not scale..
>
> stmmac can call init function multiple times, so you would be parsing DT
> and also remapping the address multiple times.

I should save the mapped address, and check if it was mapped before.
Or we could split it into .probe and .init, where .probe is call in
stmmac_pltfr_probe, and .init is called in stmmac_open.

> [---
>> +const struct plat_stmmacenet_data sun7i_gmac_data = {
>> +     .has_gmac = 1,
>> +     .tx_coe = 1,
>> +     .init = sun7i_gmac_init,
>> +};
>> +
> ---]
>
> This looks exactly like a AUXDATA way of doing things.
> Again stmmac driver has to make a copy of this so that I would not get a
> same copy for multiple instances.

In the patch series, stmmac will make a copy.
Though that part needs some fixes.

On a side note, the impression I got for not using AUXDATA is that it pushes
what is supposed to be driver extensions to the SoC/board specific code areas.

>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> index f16a9bd..c6e1f93 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
>> @@ -130,6 +130,9 @@ void stmmac_disable_eee_mode(struct stmmac_priv *priv);
>>  bool stmmac_eee_init(struct stmmac_priv *priv);
>>
>
>
> [...
>>  #ifdef CONFIG_STMMAC_PLATFORM
>> +#ifdef CONFIG_DWMAC_SUNXI
>> +extern const struct plat_stmmacenet_data sun7i_gmac_data;
>> +#endif
>>  extern struct platform_driver stmmac_pltfr_driver;
>>  static inline int stmmac_register_platform(void)
>>  {
>> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>> index df3fd1c..6cf8292 100644
>> --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>> +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c
>> @@ -35,6 +35,9 @@ static const struct of_device_id stmmac_dt_ids[] = {
>>       { .compatible = "snps,dwmac-3.70a"},
>>       { .compatible = "snps,dwmac-3.710"},
>>       { .compatible = "snps,dwmac"},
>> +#ifdef CONFIG_DWMAC_SUNXI
>> +     { .compatible = "allwinner,sun7i-gmac", .data = &sun7i_gmac_data},
>> +#endif
> ...]
>
> Personally, I did not want to do this kind of stuff in stmmac, As this
> list would keep growing, and this file need to be edited for every new
> SOC or every different type of glue logic.
>
> Please let me know what your opnion on doing Allwinner glue driver in
> line with http://lkml.org/lkml/2013/11/12/462


I needed to set some fields in the platform data,
as was set in the driver provided by Allwinner, and
out of our own needs.

1. .tx_coe
   This is not exported in the DT bindings.
   Looking at stmmac code, not setting this seems to disable all
   checksum offloading.

2. .force_sf_dma_mode
   I have added DT property handling for this.

3. .mdio_bus_data
   The PHY mask is something we would like to have at the board level.
   The PHY on one of our boards, RTL8211E from Realtek, responds to
   commands sent to phy address 0, regardless what it's actual address is.
   This is documented in RTL8211E's datasheet:

      The RTL8211E-VB(VL)/RTL8211EG-VB support PHY addresses from 00001 to
      00111. PHY address 0 is a broadcast from the MAC; each PHY device
      should respond.

   Without the PHY mask, probing the MDIO bus would yield two devices,
   when in reality there is only one. This results in some confusion.

   This should definitely be exported as a DT binding.

I am also unable to add a generic compatible string for our particular
dwmac, because I do not know the exact version of the IP, only that
it is earlier than 3.50. No hardware DMA capability flags.

Using something like "snps,dwmac-pre-3.50" is IMO worse.

>>       { /* sentinel */ }
>>  };
>>  MODULE_DEVICE_TABLE(of, stmmac_dt_ids);
>>
>

ChenYu
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