linux-kernel - Re: [PATCH v2 2/7] mmc: sdhci-of-arasan: Fix SDHCI_RESET

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Date:   Fri, 21 Oct 2022 10:45:36 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        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>,
        Haibo Chen <haibo.chen@....com>,
        Broadcom internal kernel review list 
        <bcm-kernel-feedback-list@...adcom.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Michal Simek <michal.simek@...inx.com>,
        Faiz Abbas <faiz_abbas@...com>, linux-mmc@...r.kernel.org,
        Jonathan Hunter <jonathanh@...dia.com>,
        Al Cooper <alcooperx@...il.com>,
        linux-arm-kernel@...ts.infradead.org,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        linux-kernel@...r.kernel.org,
        Thierry Reding <thierry.reding@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/7] mmc: sdhci-of-arasan: Fix SDHCI_RESET_ALL for
 CQHCI

On 10/19/22 23:29, Adrian Hunter wrote:
> On 20/10/22 01:19, Brian Norris wrote:
>> On Wed, Oct 19, 2022 at 02:59:39PM -0700, Florian Fainelli wrote:
>>> On 10/19/22 14:54, Brian Norris wrote:
>>>> The same bug was already found and fixed for two other drivers, in v5.7
>>>> and v5.9:
>>>>
>>>> 5cf583f1fb9c mmc: sdhci-msm: Deactivate CQE during SDHC reset
>>>> df57d73276b8 mmc: sdhci-pci: Fix SDHCI_RESET_ALL for CQHCI for Intel GLK-based controllers
>>>>
>>>> The latter is especially prescient, saying "other drivers using CQHCI
>>>> might benefit from a similar change, if they also have CQHCI reset by
>>>> SDHCI_RESET_ALL."
>>
>>>> --- a/drivers/mmc/host/sdhci-of-arasan.c
>>>> +++ b/drivers/mmc/host/sdhci-of-arasan.c
>>>> @@ -366,6 +366,9 @@ static void sdhci_arasan_reset(struct sdhci_host *host, u8 mask)
>>>>    	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>>>>    	struct sdhci_arasan_data *sdhci_arasan = sdhci_pltfm_priv(pltfm_host);
>>>> +	if ((host->mmc->caps2 & MMC_CAP2_CQE) && (mask & SDHCI_RESET_ALL))
>>>> +		cqhci_deactivate(host->mmc);
>>>> +
>>>>    	sdhci_reset(host, mask);
>>>
>>> Cannot this be absorbed by sdhci_reset() that all of these drivers appear to
>>> be utilizing since you have access to the host and the mask to make that
>>> decision?
>>
>> It potentially could.
>>
>> I don't know if this is a specified SDHCI behavior that really belongs
>> in the common helper, or if this is just a commonly-shared behavior. Per
>> the comments I quote above ("if they also have CQHCI reset by
>> SDHCI_RESET_ALL"), I chose to leave that as an implementation-specific
>> behavior.
>>
>> I suppose it's not all that harmful to do this even if some SDHCI
>> controller doesn't have the same behavior/quirk.
>>
>> I guess I also don't know if any SDHCI controllers will support command
>> queueing (MMC_CAP2_CQE) via somethings *besides* CQHCI. I see
>> CQE support in sdhci-sprd.c without CQHCI, although that driver doesn't
>> set MMC_CAP2_CQE.
> 
> SDHCI and CQHCI are separate modules and are not dependent, so they cannot
> call into each other directly (and should not).  A new CQE API would be
> needed in mmc_cqe_ops e.g. (*cqe_notify_reset)(struct mmc_host *host),
> and wrapped in mmc/host.h:
> 
> static inline void mmc_cqe_notify_reset(struct mmc_host *host)
> {
> 	if (host->cqe_ops->cqe_notify_reset)
> 		host->cqe_ops->cqe_notify_reset(host);
> }
> 
> Alternatively, you could make a new module for SDHCI/CQHCI helper functions,
> although in this case there is so little code it could be static inline and
> added in a new include file instead, say sdhci-cqhci.h e.g.
> 
> #include "cqhci.h"
> #include "sdhci.h"
> 
> static inline void sdhci_cqhci_reset(struct sdhci_host *host, u8 mask)
> {
> 	if ((host->mmc->caps2 & MMC_CAP2_CQE) && (mask & SDHCI_RESET_ALL) &&
> 	    host->mmc->cqe_private)
> 		cqhci_deactivate(host->mmc);
> 	sdhci_reset(host, mask);
> }
> 

I like the simplicity of the inline helper, especially towards 
backports. May suggest to name it sdhci_and_cqhci_reset() to illustrate 
that it does both, and does not apply specifically CQHCI that would be 
"embedded" into SDHCI, but your call here.
-- 
Florian