linux-kernel - Re: [PATCH 1/5] mmc: sdhci-of-arasan: Fix SDHCI_RESET

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Date:   Tue, 18 Oct 2022 20:58:44 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Brian Norris <briannorris@...omium.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        Faiz Abbas <faiz_abbas@...com>,
        NXP Linux Team <linux-imx@....com>,
        Haibo Chen <haibo.chen@....com>,
        Al Cooper <alcooperx@...il.com>, linux-mmc@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Thierry Reding <thierry.reding@...il.com>,
        Michal Simek <michal.simek@...inx.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        linux-arm-kernel@...ts.infradead.org,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>, stable@...r.kernel.org
Subject: Re: [PATCH 1/5] mmc: sdhci-of-arasan: Fix SDHCI_RESET_ALL for CQHCI

On 18/10/22 19:59, Brian Norris wrote:
> Hi Adrian,
> 
> On Tue, Oct 18, 2022 at 07:13:28PM +0300, Adrian Hunter wrote:
>> On 18/10/22 06:57, Brian Norris wrote:
>>> So like these other patches, deactivate CQHCI when resetting the
>>> controller. Also, move around the DT/caps handling, because
>>> sdhci_setup_host() performs resets before we've initialized CQHCI. This
>>> is the pattern followed in other SDHCI/CQHCI drivers.
>>
>> Did you consider just checking host->mmc->cqe_private like
>> sdhci_cqhci_reset() ?
> 
> I did not, although I am doing so now.
> 
> My first thought is that this feels a bit too private. Is the host
> driver supposed to be memorizing the details of the CQHCI layer?

Some drivers need to access CQHCI registers and get the reference
to cqhci_host from cqe_private, so that is already accepted.

> 
> But on the plus side, that would remove some contortions needed here
> (and also in sdhci-brcmstb.c).
> 
> Here's another option I previously considered: teaching
> cqhci_deactivate() to check cqe_private itself. That would have the same
> benefits, while keeping the private details in cqhci-core.c. How do you
> like that?

I don't mind either way.

> 
> (Tiny downside: cqhci-core.c got its rename in v5.12, so backporting
> this to -stable would get slightly more difficult.)
> 
> Brian