Re: [net-next v9 5/6] net: stmmac: Add glue layer for StarFive JH7110 SoC

[Guo Samin <samin.guo@starfivetech.com>]

Re: [net-next v9 5/6] net: stmmac: Add glue layer for StarFive JH7110 SoC
From: Jakub Kicinski <kuba@kernel.org>
to: Samin Guo <samin.guo@starfivetech.com>
data: 2023/3/29

> On Tue, 28 Mar 2023 14:20:08 +0800 Samin Guo 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>
> 
> Excellent, now it applies cleanly :)
> 
> Our clang build with W=1 complains that:
> 
> drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c:37:2: warning: variable 'rate' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized]
>         default:
>         ^~~~~~~
> drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c:42:36: note: uninitialized use occurs here
>         err = clk_set_rate(dwmac->clk_tx, rate);
>                                           ^~~~
> drivers/net/ethernet/stmicro/stmmac/dwmac-starfive.c:24:20: note: initialize the variable 'rate' to silence this warning
>         unsigned long rate;
>                           ^
>                            = 0
> 
> 
> not sure how you prefer to fix this. Maybe return early?

Hi Jakub,

Sorry, gcc I used does not report this error (:, and clang compile checks are more stringent.
Also, if return early at default node, Arun Ramadoss doesn't think it's a good idea because the function is a void type.

I think I can initialize the value of rate first by clk_get_rate (Intel did the same <dwmac-intel-plat.c: kmb_eth_fix_mac_speed >),
like this:


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->tx_clk);

        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;
        }   

        err = clk_set_rate(dwmac->clk_tx, rate);
        if (err)
                dev_err(dwmac->dev, "failed to set tx rate %lu\n", rate);
}

What do you think?


Best regards,
Samin