linux-kernel - Re: [PATCH] mmc: sdhci-msm: Slot indexing for distinguishing multiple SDCC instances

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Message-ID: <40694102-8daa-481b-b724-0a7e37dd4af1@quicinc.com>
Date: Wed, 20 Nov 2024 17:37:20 +0530
From: Sachin Gupta <quic_sachgupt@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
CC: Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson
	<ulf.hansson@...aro.org>, <linux-arm-msm@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <quic_cang@...cinc.com>, <quic_nguyenb@...cinc.com>,
        <quic_bhaskarv@...cinc.com>, <quic_mapa@...cinc.com>,
        <quic_narepall@...cinc.com>, <quic_nitirawa@...cinc.com>,
        <quic_rampraka@...cinc.com>, <quic_sartgarg@...cinc.com>
Subject: Re: [PATCH] mmc: sdhci-msm: Slot indexing for distinguishing multiple
 SDCC instances



On 10/28/2024 5:56 PM, Dmitry Baryshkov wrote:
> On Mon, Oct 28, 2024 at 04:10:37PM +0530, Sachin Gupta wrote:
>>
>>
>> On 10/25/2024 6:03 PM, Adrian Hunter wrote:
>>> On 25/10/24 13:37, Sachin Gupta wrote:
>>>>
>>>>
>>>> On 10/24/2024 4:38 PM, Adrian Hunter wrote:
>>>>> On 22/10/24 17:18, Sachin Gupta wrote:
>>>>>> This update addresses the requirement for accurate slot indexing
>>>>>> in the sdhci-msm driver to differentiate between multiple SDCC
>>>>>> (Secure Digital Card Controller) instances, such as eMMC, SD card,
>>>>>> and SDIO.
>>>>>>
>>>>>> Additionally, it revises the slot indexing logic to comply with
>>>>>> the new device tree (DT) specifications.
>>>>>
>>>>> This patch seems incomplete because all it does is assign a global
>>>>> variable which is never used again.
>>>>>
>>>>
>>>> Qualcomm internal debugging tools utilize this global variable to
>>>> access and differentiate between all the instance's sdhci_msm_host
>>>> data structure (eMMC, SD card, and SDIO).
>>>
>>> The kernel does not accept code that does not serve a functional
>>> purpose.
>>>
>>> You could look at using eBPF or KGDB to get the information,
>>> otherwise you might just have to carry that kind of patch in
>>> your internal tree.
>>>
>>
>> Sorry for misleading sentence, the tool I use is lauterbach Trace32 and when
>> using Lauterbach Trace32 tool, having a global variable makes it easier to
>> load and inspect dumps. It will be easy to quickly locate and analyze the
>> sdhci_msm_host structure, which speeds up the debugging process.
> 
> This still isn't a functional purpose. This is a debugging code for a
> particular developer debugging SDHCI issues.
> 

Thanks for your comment and time we will explore more on this.

>>>>>> Signed-off-by: Ram Prakash Gupta <quic_rampraka@...cinc.com>
>>>>>> Signed-off-by: Sarthak Garg <quic_sartgarg@...cinc.com>
>>>>>> Signed-off-by: Maramaina Naresh <quic_mnaresh@...cinc.com>
>>>>>> Signed-off-by: Ziqi Chen <quic_ziqichen@...cinc.com>
>>>>>> Signed-off-by: Sachin Gupta <quic_sachgupt@...cinc.com>
>>>>>> ---
>>>>>>     drivers/mmc/host/sdhci-msm.c | 10 ++++++++++
>>>>>>     1 file changed, 10 insertions(+)
>>>>>>
>>>>>> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
>>>>>> index e113b99a3eab..3cb79117916f 100644
>>>>>> --- a/drivers/mmc/host/sdhci-msm.c
>>>>>> +++ b/drivers/mmc/host/sdhci-msm.c
>>>>>> @@ -292,6 +292,8 @@ struct sdhci_msm_host {
>>>>>>         bool vqmmc_enabled;
>>>>>>     };
>>>>>>     +static struct sdhci_msm_host *sdhci_slot[3];
>>>>>> +
>>>>>>     static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
>>>>>>     {
>>>>>>         struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>>>>> @@ -2426,6 +2428,14 @@ static int sdhci_msm_probe(struct platform_device *pdev)
>>>>>>         if (ret)
>>>>>>             goto pltfm_free;
>>>>>>     +    if (node) {
>>>>>> +        ret = of_alias_get_id(pdev->dev.of_node, "mmc");
>>>>>> +        if (ret < 0)
>>>>>> +            dev_err(&pdev->dev, "get slot index failed %d\n", ret);
>>>>>> +        else
>>>>>> +            sdhci_slot[ret] = msm_host;
>>>>>> +    }
>>>>>> +
>>>>>>         /*
>>>>>>          * Based on the compatible string, load the required msm host info from
>>>>>>          * the data associated with the version info.
>>>>>
>>>>
>>>
>>
>