linux-kernel - Re: [PATCH v4 08/18] net: davinci_emac: potentially get the MAC address from MTD

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Message-ID: <CAMpxmJV2kC+Na5uiWsTtBtSev65ba3+jZhzzeoktXR0TAQQtKw@mail.gmail.com>
Date:   Mon, 2 Jul 2018 09:41:36 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     David Lechner <david@...hnology.com>
Cc:     Bartosz Golaszewski <brgl@...ev.pl>, Sekhar Nori <nsekhar@...com>,
        Kevin Hilman <khilman@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Grygorii Strashko <grygorii.strashko@...com>,
        "David S . Miller" <davem@...emloft.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Lukas Wunner <lukas@...ner.de>, Rob Herring <robh@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>, Jonathan Corbet <corbet@....net>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-OMAP <linux-omap@...r.kernel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH v4 08/18] net: davinci_emac: potentially get the MAC
 address from MTD

2018-06-29 22:35 GMT+02:00 David Lechner <david@...hnology.com>:
> On 06/29/2018 03:09 PM, David Lechner wrote:
>>
>> On 06/29/2018 04:40 AM, Bartosz Golaszewski wrote:
>>>
>>> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>>
>>> On da850-evm board we can read the MAC address from MTD. It's currently
>>> done in the relevant board file, but we want to get rid of all the MAC
>>> reading callbacks from the board file (SPI and NAND). Move the reading
>>> of the MAC address from SPI to the emac driver's probe function.
>>>
>>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
>>> ---
>>>   drivers/net/ethernet/ti/davinci_emac.c | 20 ++++++++++++++++++--
>>>   1 file changed, 18 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/net/ethernet/ti/davinci_emac.c
>>> b/drivers/net/ethernet/ti/davinci_emac.c
>>> index a1a6445b5a7e..48e6a7755811 100644
>>> --- a/drivers/net/ethernet/ti/davinci_emac.c
>>> +++ b/drivers/net/ethernet/ti/davinci_emac.c
>>> @@ -67,7 +67,7 @@
>>>   #include <linux/of_irq.h>
>>>   #include <linux/of_net.h>
>>>   #include <linux/mfd/syscon.h>
>>> -
>>> +#include <linux/mtd/mtd.h>
>>>   #include <asm/irq.h>
>>>   #include <asm/page.h>
>>> @@ -1783,7 +1783,10 @@ static int davinci_emac_probe(struct
>>> platform_device *pdev)
>>>       struct cpdma_params dma_params;
>>>       struct clk *emac_clk;
>>>       unsigned long emac_bus_frequency;
>>> -
>>> +#ifdef CONFIG_MTD
>>> +    size_t mac_addr_len;
>>> +    struct mtd_info *mtd;
>>> +#endif /* CONFIG_MTD */
>>>       /* obtain emac clock from kernel */
>>>       emac_clk = devm_clk_get(&pdev->dev, NULL);
>>> @@ -1815,6 +1818,19 @@ static int davinci_emac_probe(struct
>>> platform_device *pdev)
>>>           goto err_free_netdev;
>>>       }
>>> +#ifdef CONFIG_MTD
>>
>>
>> What about the case when MTD is compiled as a module?
>>
>>> +    mtd = get_mtd_device_nm("MAC-Address");
>>
>>
>> What about the case when PTR_ERR(mtd) == -EPROBE_DEFER?
>
>
> To answer my own question: because get_mtd_device_nm() doesn't
> ever return -EPROBE_DEFER.
>
> I'm trying to make this work on LCDK, but the emac driver probes
> before any mtd device is registered, so, I just get -ENODEV even
> though I've added a partition to the device tree labeled
> "MAC-Address". You can see in the kernel messages that MTD is
> not probed until later.
>

I tested it on da850-evm - all MTD & SPI related modules need to be
built-in for it to work, so:

CONFIG_MTD=y
CONFIG_MTD_M25P80=y
CONFIG_SPI_DAVINCI=y

Best regards,
Bartosz Golaszewski

>
>>
>>> +    if (!IS_ERR(mtd)) {
>>> +        rc = mtd_read(mtd, 0, ETH_ALEN,
>>> +                  &mac_addr_len, priv->mac_addr);
>>> +        if (rc == 0)
>>> +            dev_info(&pdev->dev,
>>> +                 "Read MAC addr from SPI Flash: %pM\n",
>>> +                 priv->mac_addr);
>>> +        put_mtd_device(mtd);
>>> +    }
>>> +#endif /* CONFIG_MTD */
>>> +
>>>       /* MAC addr and PHY mask , RMII enable info from platform_data */
>>>       memcpy(priv->mac_addr, pdata->mac_addr, ETH_ALEN);
>>>       priv->phy_id = pdata->phy_id;
>>>
>>
>