linux-kernel - Re: [PATCH V2 1/2] mmc: sdhci: Request regulators before reading capabilities

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <57906E2C.9000200@intel.com>
Date:	Thu, 21 Jul 2016 09:39:40 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Adrian Hunter <adrian.hunter@...el.com>,
	Jon Hunter <jonathanh@...dia.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Alexandre Courbot <gnurou@...il.com>
Cc:	linux-mmc@...r.kernel.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] mmc: sdhci: Request regulators before reading
 capabilities

On 20/07/16 16:04, Adrian Hunter wrote:
> On 20/07/16 16:02, Adrian Hunter wrote:
>> On 12/07/16 16:53, Jon Hunter wrote:
>>> The capabilities of the SDHCI host controller are read early during the
>>> SDHCI host initialisation in sdhci_setup_host() and before any
>>> regulators for the host have been requested. This means that if the host
>>> supports some high-speed modes (according to its capabilities register),
>>> but the board cannot because the appropriate voltage regulator is not
>>> available, then the host cannot easily override the capabilities that
>>> are supported.
>>>
>>> To allow a SDHCI host controller to determine if it can support high
>>> speed modes via the presense of the MMC regulators, request the
>>
>> Try not to confuse High Speed mode with UHS modes.
>>
>> presense -> presence
>>
>>> regulators before reading the capabilites of the host controller. This
>>
>> capabilites -> capabilities
>>
>>> will allow the SDHCI host to use the 'reset' callback to take the
>>> appropriate action (set flags, configure registers, etc) before the
>>> capabilities register(s) are read.
>>>
>>> Please note that some SDHCI hosts, such as the Tegra SDHCI host, has
>>> the ability to mask bits in the capabilities register to prevent
>>> certain capabilities from being advertised.
>>>
>>> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
>>> ---
>>>
>>> Although this is described as a "V2" this patch has been added since
>>> the original patch was posted.
>>>
>>> If the below is deemed not appropriate, then another solution I was
>>> thinking of is to allow the SDHCI host to call 'mmc_regulator_get_supply'
>>> before calling sdhci_setup_host() and then in sdhci_setup_host() check
>>> if any regulators are already present before calling
>>> mmc_regulator_get_supply().
>>
>> And we can still do that later if we need to.
>>
>>>
>>>  drivers/mmc/host/sdhci.c | 16 +++++++++++-----
>>>  1 file changed, 11 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>> index 2ee8bfa77116..628c4b3558c0 100644
>>> --- a/drivers/mmc/host/sdhci.c
>>> +++ b/drivers/mmc/host/sdhci.c
>>> @@ -3021,6 +3021,17 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>  
>>>  	mmc = host->mmc;
>>>  
>>> +	/*
>>> +	 * If there are external regulators, get them. Note
>>> +	 * this must be done early before resetting the host
>>> +	 * and reading the capabilities so that the host can
>>> +	 * take the appropriate action if regulators are not
>>> +	 * available.
> 
> Also you could spread this comment out to 80 columns.
> 
>>> +	 */
>>> +	ret = mmc_regulator_get_supply(mmc);
>>> +	if (ret == -EPROBE_DEFER)
>>> +		return ret;
>>> +
>>>  	sdhci_read_caps(host);
>>>  
>>>  	override_timeout_clk = host->timeout_clk;
>>> @@ -3253,11 +3264,6 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>  	    mmc_gpio_get_cd(host->mmc) < 0)
>>>  		mmc->caps |= MMC_CAP_NEEDS_POLL;
>>>  
>>> -	/* If there are external regulators, get them */
>>> -	ret = mmc_regulator_get_supply(mmc);
>>> -	if (ret == -EPROBE_DEFER)
>>> -		goto undma;
>>
>> All goto's before this now need to goto unreg.

Er, actually they don't!

So apart from the cosmetics above:

Acked-by: Adrian Hunter <adrian.hunter@...el.com>

>>
>>> -
>>>  	/* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
>>>  	if (!IS_ERR(mmc->supply.vqmmc)) {
>>>  		ret = regulator_enable(mmc->supply.vqmmc);
>>>
>>
>>
> 
>