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    SubjectRe: [PATCH v4 10/10] mtd: rawnand: stm32_fmc2: get resources from parent node
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    Hi Miquel,

    On 5/11/20 2:58 PM, Miquel Raynal wrote:
    > Hi Christophe,
    >
    > Christophe Kerello <christophe.kerello@st.com> wrote on Mon, 11 May
    > 2020 14:47:09 +0200:
    >
    >> Hi Miquel,
    >>
    >> On 5/11/20 1:59 PM, Miquel Raynal wrote:
    >>> Hi Christophe,
    >>>
    >>> Christophe Kerello <christophe.kerello@st.com> wrote on Mon, 11 May
    >>> 2020 12:21:03 +0200:
    >>>
    >>>> Hi Miquel,
    >>>>
    >>>> On 5/11/20 11:18 AM, Miquel Raynal wrote:
    >>>>> Hi Christophe,
    >>>>>
    >>>>> Christophe Kerello <christophe.kerello@st.com> wrote on Wed, 6 May 2020
    >>>>> 11:11:19 +0200:
    >>>>> >>>> FMC2 EBI support has been added. Common resources (registers base
    >>>>>> and clock) are now shared between the 2 drivers. It means that the
    >>>>>> common resources should now be found in the parent device when EBI
    >>>>>> node is available.
    >>>>>>
    >>>>>> Signed-off-by: Christophe Kerello <christophe.kerello@st.com>
    >>>>>> ---
    >>>>>
    >>>>> [...]
    >>>>> >>>> +
    >>>>>> +static bool stm32_fmc2_nfc_check_for_parent(struct platform_device *pdev)
    >>>>>> +{
    >>>>>> + u32 i;
    >>>>>> + int nb_resources = 0;
    >>>>>> +
    >>>>>> + /* Count the number of resources in reg property */
    >>>>>> + for (i = 0; i < pdev->num_resources; i++) {
    >>>>>> + struct resource *res = &pdev->resource[i];
    >>>>>> +
    >>>>>> + if (resource_type(res) == IORESOURCE_MEM)
    >>>>>> + nb_resources++;
    >>>>>> + }
    >>>>>> +
    >>>>>> + /* Each CS needs 3 resources defined (data, cmd and addr) */
    >>>>>> + if (nb_resources % 3)
    >>>>>> + return false;
    >>>>>> +
    >>>>>> + return true;
    >>>>>> +}
    >>>>>
    >>>>> This function looks fragile. Why not just checking the compatible
    >>>>> string of the parent node?
    >>>>> >>
    >>>> Yes, it is another way to check that we have an EBI parent node.
    >>>>
    >>>> In this implementation, I was checking the number of reg tuples.
    >>>> In case we have 6, it means that the register base address is defined in the parent node (EBI node).
    >>>> In case we have 7, it means that the register base address is defined in the current node (NFC node).
    >>>
    >>> Yes, I understand what you are doing, but I kind of dislike the logic.
    >>> Relying on the number of reg tuples is something that can be done (I
    >>> used it myself one time), but I think this is more a hack that you do
    >>> when you have no other way to differentiate. I guess the proper way
    >>> would be to look at the parent's compatible. If it matches what you
    >>> expect, then you can store the dev->of_node->parent->dev somewhere in
    >>> your controller's structure and then use it to initialize the clock and
    >>> regmap. This way you don't have to move anything else in the probe path.
    >>>
    >>
    >> OK, I will check the compatible string of the parent device using of_device_is_compatible API in v5.
    >> In case of the parent is found, I will add it in the structure of the controller (dev_parent).
    >> I will rely on this field only to get the common resources (the register base address and the clock) in the NFC node or in the EBI node.
    >
    > I had something slightly different in mind: what about setting a
    > default value to this field as being the controller's device itself.
    > This way, once it is set to either the parent device or the device
    > itself, you can use it "blindly" in your devm_clk_get/regmap_init calls?
    >

    I will try to explain what I have in mind.

    I will add a new field in the structure of the controller (not called
    dev_parent but cdev)
    struct device *cdev;

    Then, at probe time, this field will be assigned:
    nfc->cdev = of_device_is_compatible(dev->parent->of_node, "bla bla") :
    dev->parent ? dev;

    For the clock, it will be
    nfc->clk = devm_clk_get(nfc->cdev, NULL);

    For the register base, I need to replace:
    res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    mmio = devm_ioremap_resource(dev, res);
    if (IS_ERR(mmio))
    return PTR_ERR(mmio);

    nfc->regmap = devm_regmap_init_mmio(dev, mmio, &stm32_fmc2_regmap_cfg);
    if (IS_ERR(nfc->regmap))
    return PTR_ERR(nfc->regmap);

    nfc->io_phys_addr = res->start;

    With:

    ret = of_address_to_resource(nfc->cdev->of_node, 0, &res);
    if (ret)
    return ret;

    nfc->io_phys_addr = res.start;

    nfc->regmap = device_node_to_regmap(nfc->cdev->of_node);
    if (IS_ERR(nfc->regmap))
    return PTR_ERR(nfc->regmap);

    I expect that you were thinking about something like this proposal.

    Regards,
    Christophe Kerello.

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