linux-kernel - Re: [PATCH V5 02/26] mmc: core: Prepare to support SD UHS-II cards

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Date:   Fri, 4 Nov 2022 13:16:31 +0100
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Victor Shih <victorshihgli@...il.com>, ulf.hansson@...aro.org,
        adrian.hunter@...el.com
Cc:     linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
        benchuanggli@...il.com, HL.Liu@...esyslogic.com.tw,
        Greg.tu@...esyslogic.com.tw, takahiro.akashi@...aro.org,
        dlunev@...omium.org, Victor Shih <victor.shih@...esyslogic.com.tw>
Subject: Re: [PATCH V5 02/26] mmc: core: Prepare to support SD UHS-II cards

Le 19/10/2022 à 13:06, Victor Shih a écrit :
> From: Ulf Hansson <ulf.hansson@...aro.org>
> 
> Updates in V4:
>   - Re-based, updated a comment and removed white-space.
>   - Moved MMC_VQMMC2_VOLTAGE_180 into a later patch in the series.
> 
> Update in previous version:
> The SD UHS-II interface was introduced to the SD spec v4.00 several years
> ago. The interface is fundamentally different from an electrical and a
> protocol point of view, comparing to the legacy SD interface.
> 
> However, the legacy SD protocol is supported through a specific transport
> layer (SD-TRAN) defined in the UHS-II addendum of the spec. This allows the
> SD card to be managed in a very similar way as a legacy SD card, hence a
> lot of code can be re-used to support these new types of cards through the
> mmc subsystem.
> 
> Moreover, an SD card that supports the UHS-II interface shall also be
> backwards compatible with the legacy SD interface, which allows a UHS-II
> card to be inserted into a legacy slot. As a matter of fact, this is
> already supported by mmc subsystem as of today.
> 
> To prepare to add support for UHS-II, this change puts the basic foundation
> in the mmc core in place, allowing it to be more easily reviewed before
> subsequent changes implements the actual support.
> 
> Basically, the approach here adds a new UHS-II bus_ops type and adds a
> separate initialization path for the UHS-II card. The intent is to avoid us
> from sprinkling the legacy initialization path, but also to simplify
> implementation of the UHS-II specific bits.
> 
> At this point, there is only one new host ops added to manage the various
> ios settings needed for UHS-II. Additional host ops that are needed, are
> being added from subsequent changes.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> ---

[]

> +static int sd_uhs2_attach(struct mmc_host *host)
> +{
> +	int err;
> +
> +	err = sd_uhs2_power_up(host);
> +	if (err)
> +		goto err;
> +
> +	err = sd_uhs2_phy_init(host);
> +	if (err)
> +		goto err;
> +
> +	err = sd_uhs2_init_card(host);
> +	if (err)
> +		goto err;
> +
> +	mmc_attach_bus(host, &sd_uhs2_ops);
> +
> +	mmc_release_host(host);
> +
> +	err = mmc_add_card(host->card);
> +	if (err)
> +		goto remove_card;
> +
> +	mmc_claim_host(host);
> +	return 0;
> +
> +remove_card:
> +	mmc_remove_card(host->card);

Hi,

If we arrive here, mmc_add_card() has failed.
is it correct to call mmc_remove_card() in such a case?

> +	host->card = NULL;
> +	mmc_claim_host(host);
> +	mmc_detach_bus(host);
> +err:
> +	sd_uhs2_power_off(host);

If sd_uhs2_power_up() fails, we arrive here.
Is its correct to call sd_uhs2_power_off() in such a case, or should we 
return directly if sd_uhs2_power_up() fails?

CJ

> +	return err;
> +}
> +

[]