Re: [-net-next v11 5/6] net: stmmac: Add glue layer for StarFive JH7110 SoC

[Paolo Abeni <pabeni@redhat.com>]

On Mon, 2023-04-10 at 16:29 +0800, Guo Samin wrote:
> Re: [-net-next v11 5/6] net: stmmac: Add glue layer for StarFive JH7110 SoC
> From: Emil Renner Berthing <emil.renner.berthing@canonical.com>
> to: Guo Samin <samin.guo@starfivetech.com>
> data: 2023/4/9
> 
> > On Sat, 8 Apr 2023 at 03:16, Guo Samin <samin.guo@starfivetech.com> wrote:
> > > 
> > >  Re: [-net-next v11 5/6] net: stmmac: Add glue layer for StarFive JH7110 SoC
> > > From: Emil Renner Berthing <emil.renner.berthing@canonical.com>
> > > to: Samin Guo <samin.guo@starfivetech.com>
> > > data: 2023/4/8
> > > 
> > > > On Fri, 7 Apr 2023 at 13:05, Samin Guo <samin.guo@starfivetech.com> wrote:
> > > > > 
> > > > > This adds StarFive dwmac driver support on the StarFive JH7110 SoC.
> > > > > 
> > > > > Tested-by: Tommaso Merciai <tomm.merciai@gmail.com>
> > > > > Co-developed-by: Emil Renner Berthing <kernel@esmil.dk>
> > > > > Signed-off-by: Emil Renner Berthing <kernel@esmil.dk>
> > > > > Signed-off-by: Samin Guo <samin.guo@starfivetech.com>
> > > > > ---
> > > > >  MAINTAINERS                                   |   1 +
> > > > >  drivers/net/ethernet/stmicro/stmmac/Kconfig   |  12 ++
> > > > >  drivers/net/ethernet/stmicro/stmmac/Makefile  |   1 +
> > > > >  .../ethernet/stmicro/stmmac/dwmac-starfive.c  | 123 ++++++++++++++++++
> > > > >  4 files changed, 137 insertions(+)
> > > > >  create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c
> > > > > 
> > > > > diff --git a/MAINTAINERS b/MAINTAINERS
> > > > > index 6b6b67468b8f..46b366456cee 100644
> > > > > --- a/MAINTAINERS
> > > > > +++ b/MAINTAINERS
> > > > > @@ -19910,6 +19910,7 @@ M:      Emil Renner Berthing <kernel@esmil.dk>
> > > > >  M:     Samin Guo <samin.guo@starfivetech.com>
> > > > >  S:     Maintained
> > > > >  F:     Documentation/devicetree/bindings/net/starfive,jh7110-dwmac.yaml
> > > > > +F:     drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c
> > > > > 
> > > > >  STARFIVE JH7100 CLOCK DRIVERS
> > > > >  M:     Emil Renner Berthing <kernel@esmil.dk>
> > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/Kconfig b/drivers/net/ethernet/stmicro/stmmac/Kconfig
> > > > > index f77511fe4e87..5f5a997f21f3 100644
> > > > > --- a/drivers/net/ethernet/stmicro/stmmac/Kconfig
> > > > > +++ b/drivers/net/ethernet/stmicro/stmmac/Kconfig
> > > > > @@ -165,6 +165,18 @@ config DWMAC_SOCFPGA
> > > > >           for the stmmac device driver. This driver is used for
> > > > >           arria5 and cyclone5 FPGA SoCs.
> > > > > 
> > > > > +config DWMAC_STARFIVE
> > > > > +       tristate "StarFive dwmac support"
> > > > > +       depends on OF && (ARCH_STARFIVE || COMPILE_TEST)
> > > > > +       select MFD_SYSCON
> > > > > +       default m if ARCH_STARFIVE
> > > > > +       help
> > > > > +         Support for ethernet controllers on StarFive RISC-V SoCs
> > > > > +
> > > > > +         This selects the StarFive platform specific glue layer support for
> > > > > +         the stmmac device driver. This driver is used for StarFive JH7110
> > > > > +         ethernet controller.
> > > > > +
> > > > >  config DWMAC_STI
> > > > >         tristate "STi GMAC support"
> > > > >         default ARCH_STI
> > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/Makefile b/drivers/net/ethernet/stmicro/stmmac/Makefile
> > > > > index 057e4bab5c08..8738fdbb4b2d 100644
> > > > > --- a/drivers/net/ethernet/stmicro/stmmac/Makefile
> > > > > +++ b/drivers/net/ethernet/stmicro/stmmac/Makefile
> > > > > @@ -23,6 +23,7 @@ obj-$(CONFIG_DWMAC_OXNAS)     += dwmac-oxnas.o
> > > > >  obj-$(CONFIG_DWMAC_QCOM_ETHQOS)        += dwmac-qcom-ethqos.o
> > > > >  obj-$(CONFIG_DWMAC_ROCKCHIP)   += dwmac-rk.o
> > > > >  obj-$(CONFIG_DWMAC_SOCFPGA)    += dwmac-altr-socfpga.o
> > > > > +obj-$(CONFIG_DWMAC_STARFIVE)   += dwmac-starfive.o
> > > > >  obj-$(CONFIG_DWMAC_STI)                += dwmac-sti.o
> > > > >  obj-$(CONFIG_DWMAC_STM32)      += dwmac-stm32.o
> > > > >  obj-$(CONFIG_DWMAC_SUNXI)      += dwmac-sunxi.o
> > > > > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c
> > > > > new file mode 100644
> > > > > index 000000000000..4963d4008485
> > > > > --- /dev/null
> > > > > +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c
> > > > > @@ -0,0 +1,123 @@
> > > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > > +/*
> > > > > + * StarFive DWMAC platform driver
> > > > > + *
> > > > > + * Copyright (C) 2021 Emil Renner Berthing <kernel@esmil.dk>
> > > > > + * Copyright (C) 2022 StarFive Technology Co., Ltd.
> > > > > + *
> > > > > + */
> > > > > +
> > > > > +#include <linux/mfd/syscon.h>
> > > > > +#include <linux/of_device.h>
> > > > > +#include <linux/regmap.h>
> > > > > +
> > > > > +#include "stmmac_platform.h"
> > > > > +
> > > > > +struct starfive_dwmac {
> > > > > +       struct device *dev;
> > > > > +       struct clk *clk_tx;
> > > > > +};
> > > > > +
> > > > > +static void starfive_dwmac_fix_mac_speed(void *priv, unsigned int speed)
> > > > > +{
> > > > > +       struct starfive_dwmac *dwmac = priv;
> > > > > +       unsigned long rate;
> > > > > +       int err;
> > > > > +
> > > > > +       rate = clk_get_rate(dwmac->clk_tx);
> > > > 
> > > > Hi Samin,
> > > > 
> > > > I'm not sure why you added this line in this revision. If it's just to
> > > > not call clk_set_rate on the uninitialized rate, I'd much rather you
> > > > just returned early and don't call clk_set_rate at all in case of
> > > > errors.
> > > > 
> > > > > +
> > > > > +       switch (speed) {
> > > > > +       case SPEED_1000:
> > > > > +               rate = 125000000;
> > > > > +               break;
> > > > > +       case SPEED_100:
> > > > > +               rate = 25000000;
> > > > > +               break;
> > > > > +       case SPEED_10:
> > > > > +               rate = 2500000;
> > > > > +               break;
> > > > > +       default:
> > > > > +               dev_err(dwmac->dev, "invalid speed %u\n", speed);
> > > > > +               break;
> > > > 
> > > > That is skip the clk_get_rate above and just change this break to a return.
> > > > 
> > > 
> > > Hi Emil,
> > > 
> > > We used the solution you mentioned before V3, but Arun Ramadoss doesn't think that's great.
> > > (https://patchwork.kernel.org/project/linux-riscv/patch/20230106030001.1952-6-yanhong.wang@starfivetech.com)
> > > 
> > > 
> > > > +static void starfive_eth_plat_fix_mac_speed(void *priv, unsigned int
> > > > speed)
> > > > +{
> > > > +     struct starfive_dwmac *dwmac = priv;
> > > > +     unsigned long rate;
> > > > +     int err;
> > > > +
> > > > +     switch (speed) {
> > > > +     case SPEED_1000:
> > > > +             rate = 125000000;
> > > > +             break;
> > > > +     case SPEED_100:
> > > > +             rate = 25000000;
> > > > +             break;
> > > > +     case SPEED_10:
> > > > +             rate = 2500000;
> > > > +             break;
> > > > +     default:
> > > > +             dev_err(dwmac->dev, "invalid speed %u\n", speed);
> > > > +             return;
> > > 
> > > Do we need to return value, since it is invalid speed. But the return
> > > value of function is void.(Arun Ramadoss)
> > > 
> > > 
> > > So in v9, after discussing with Jakub Kicinski, the clk_set_rate was used to initialize the rate.
> > > (It is a reference to Intel's scheme:    dwmac-intel-plat.c: kmb_eth_fix_mac_speed)
> > > (https://patchwork.kernel.org/project/linux-riscv/patch/20230328062009.25454-6-samin.guo@starfivetech.com)
> > > 
> > 
> > Yeah, I think this is a misunderstanding and Arun is considering if we
> > ought to return the error which we can't without changing generic
> > dwmac code, and Jakub is rightly concerned about using a local
> > variable uninitialized. I don't think anyone is suggesting that
> > getting the rate just to set it to the exact same value is better than
> > just leaving the clock alone.
> > 
> HI Emil,
> 
> Yeah, return early saves time and code complexity, and seems like a good solution so Yanhong did the same before v3. (Jakub has suggested it before),
> I wonder if Arun or other maintainers accept this solution or if there are other solutions?

I think is not a big deal either way.

To avoid too much back and forth I'll stick to the current code.

Please address Emil comment on patch 6/6

Thanks!

Paolo


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