linux-kernel - Re: [PATCH v2 2/2] mmc: sdhci-npcm: Add NPCM SDHCI driver

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Message-ID: <c200557f-c30a-62f9-287a-af804e818cf1@intel.com>
Date:   Mon, 5 Dec 2022 15:41:39 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     ulf.hansson@...aro.org, avifishman70@...il.com,
        tali.perry1@...il.com, joel@....id.au, venture@...gle.com,
        yuenn@...gle.com, benjaminfair@...gle.com,
        skhan@...uxfoundation.org, davidgow@...gle.com,
        pbrobinson@...il.com, gsomlo@...il.com, briannorris@...omium.org,
        arnd@...db.de, krakoczy@...micro.com, openbmc@...ts.ozlabs.org,
        linux-mmc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Tomer Maimon <tmaimon77@...il.com>
Subject: Re: [PATCH v2 2/2] mmc: sdhci-npcm: Add NPCM SDHCI driver

On 5/12/22 15:25, Andy Shevchenko wrote:
> On Mon, Dec 5, 2022 at 1:20 PM Tomer Maimon <tmaimon77@...il.com> wrote:
>> On Mon, 5 Dec 2022 at 12:54, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
>>> On Mon, Dec 5, 2022 at 10:54 AM Tomer Maimon <tmaimon77@...il.com> wrote:
> 
> ...
> 
>>>> +#include <linux/clk.h>
>>>> +#include <linux/err.h>
>>>> +#include <linux/io.h>
>>>> +#include <linux/mmc/host.h>
>>>> +#include <linux/mmc/mmc.h>
>>>> +#include <linux/module.h>
>>>
>>> I guess platform_device.h is missing here.
>> Build and work without platform_device.h, do I need it for module use?
> 
> The rule of thumb is to include headers we are the direct user of. I
> believe you have a data type and API that are defined in that header.
> 
> ...
> 
>>>> +static int npcm_sdhci_probe(struct platform_device *pdev)
>>>> +{
>>>> +       struct sdhci_pltfm_host *pltfm_host;
>>>> +       struct sdhci_host *host;
>>>> +       u32 caps;
>>>> +       int ret;
>>>> +
>>>> +       host = sdhci_pltfm_init(pdev, &npcm_sdhci_pdata, 0);
>>>> +       if (IS_ERR(host))
>>>> +               return PTR_ERR(host);
>>>> +
>>>> +       pltfm_host = sdhci_priv(host);
>>>
>>>> +       pltfm_host->clk = devm_clk_get_optional(&pdev->dev, NULL);
>>>
>>> You can't mix devm with non-devm in this way.
>> Can you explain what you mean You can't mix devm with non-devm in this
>> way, where is the mix?
>> In version 1 used devm_clk_get, is it problematic?
> 
> devm_ is problematic in your case.
> TL;DR: you need to use clk_get_optional() and clk_put().

devm_ calls exactly those, so what is the issue?

> 
> Your ->remove() callback doesn't free resources in the reversed order
> which may or, by luck, may not be the case of all possible crashes,
> UAFs, races, etc during removal stage. All the same for error path in
> ->probe().
> 
>>>> +       if (IS_ERR(pltfm_host->clk))
>>>> +               return PTR_ERR(pltfm_host->clk);
>>>> +
>>>> +       ret = clk_prepare_enable(pltfm_host->clk);
>>>> +       if (ret)
>>>> +               return ret;
>>>> +
>>>> +       caps = sdhci_readl(host, SDHCI_CAPABILITIES);
>>>> +       if (caps & SDHCI_CAN_DO_8BIT)
>>>> +               host->mmc->caps |= MMC_CAP_8_BIT_DATA;
>>>> +
>>>> +       ret = mmc_of_parse(host->mmc);
>>>> +       if (ret)
>>>> +               goto err_sdhci_add;
>>>> +
>>>> +       ret = sdhci_add_host(host);
>>>> +       if (ret)
>>>> +               goto err_sdhci_add;
>>>
>>> Why can't you use sdhci_pltfm_register()?
>> two things are missing in sdhci_pltfm_register
>> 1. clock.
> 
> Taking into account the implementation of the corresponding
> _unregister() I would add the clock handling to the _register() one.
> Perhaps via a new member of the platform data that supplies the name
> and index of the clock and hence all clk_get_optional() / clk_put will
> be moved there.
> 
>> 2. Adding SDHCI_CAN_DO_8BIT capability according the eMMC capabilities.
> 
> All the same, why can't platform data be utilised for this?
> 
>>>> +       return 0;
>>>> +
>>>> +err_sdhci_add:
>>>> +       clk_disable_unprepare(pltfm_host->clk);
>>>> +       sdhci_pltfm_free(pdev);
>>>> +       return ret;
>>>> +}
>