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

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Message-ID: <2knkpsv3nlbcolosyza3awktztv23kqweow3b3wilbehv2azre@dcldb6a37sbf>
Date: Mon, 28 Oct 2024 14:26:44 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Sachin Gupta <quic_sachgupt@...cinc.com>
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 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.

> > > > > 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.
> > > > 
> > > 
> > 
> 

-- 
With best wishes
Dmitry