linux-kernel - Re: [PATCH] i2c: designware: Do not require clock when SSCN and FFCN are provided

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]

Date:	Wed, 16 Dec 2015 08:11:12 -0600
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:	<wsa@...-dreams.de>, <lho@....com>, <Ken.Xue@....com>,
	<linux-i2c@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Jarkko Nikula <jarkko.nikula@...ux.intel.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH] i2c: designware: Do not require clock when SSCN and FFCN
 are provided

Hi Mika,

On 12/16/2015 03:42 AM, Mika Westerberg wrote:
> +Jarkko and Andy
>
> On Tue, Dec 15, 2015 at 04:38:58PM -0600, Suravee Suthikulpanit wrote:
>> The current driver uses input clock source frequency to calculate
>> values for [SS|FS]_[HC|LC] registers. However, when booting ACPI, we do not
>> currently have a good way to provide the frequency information.
>> Instead, we can leverage the SSCN and FFCN ACPI methods, which can be used
>> to directly provide these values.
>>
>> So, this patch removes the clock requirement when SSCN and FFCN
>> are provided.
>
> Actually I think the only thing you need to change is i2c_dw_init() so
> that it does not call dev->get_clk_rate_khz(dev) if *CNT values are
> already provided.

Please see below.

>
> The clk framework should work fine if the returned clock is NULL (which
> I think is your case).
>
> The driver gates clocks when the device is suspended and on Intel LPSS
> there actually is a clock that gets gated.
>
>> [..]
>> @@ -203,13 +223,11 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
>>   		dev->master_cfg =  DW_IC_CON_MASTER | DW_IC_CON_SLAVE_DISABLE |
>>   			DW_IC_CON_RESTART_EN | DW_IC_CON_SPEED_FAST;
>>
>> -	dev->clk = devm_clk_get(&pdev->dev, NULL);
>> -	dev->get_clk_rate_khz = i2c_dw_get_clk_rate_khz;
>> -	if (IS_ERR(dev->clk))
>> -		return PTR_ERR(dev->clk);

Actually, if we don't provide the clock (which is the case for ACPI), 
this would also return and cause the probing to fail.

Thanks,
Suravee
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/