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

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Date:   Thu, 20 Oct 2022 09:29:10 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Brian Norris <briannorris@...omium.org>,
        Florian Fainelli <f.fainelli@...il.com>
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 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);
}