linux-kernel - Re: [PATCH v1] usb: phy: tegra: Add clarifying comments about the shared registers

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Date:   Mon, 3 Feb 2020 19:26:04 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Felipe Balbi <balbi@...nel.org>, linux-usb@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] usb: phy: tegra: Add clarifying comments about the
 shared registers

03.02.2020 14:28, Thierry Reding пишет:
> On Mon, Feb 03, 2020 at 01:42:59AM +0300, Dmitry Osipenko wrote:
>> Tools like Coccinelle may erroneously recommend to use the
>> devm_platform_ioremap_resource() API for the registers mapping because
>> these tools are not aware about the implementation details of the driver.
>> Let's add a clarifying comments to the code, which should help to stop
>> future attempts to break the driver.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/usb/phy/phy-tegra-usb.c | 8 ++++++++
>>  1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/usb/phy/phy-tegra-usb.c b/drivers/usb/phy/phy-tegra-usb.c
>> index 037e8eee737d..6153cc35aba0 100644
>> --- a/drivers/usb/phy/phy-tegra-usb.c
>> +++ b/drivers/usb/phy/phy-tegra-usb.c
>> @@ -969,6 +969,10 @@ static int utmi_phy_probe(struct tegra_usb_phy *tegra_phy,
>>  		return  -ENXIO;
>>  	}
>>  
>> +	/*
>> +	 * Note that UTMI pad registers are shared by all PHYs, therefore
>> +	 * devm_platform_ioremap_resource() can't be used here.
>> +	 */
>>  	tegra_phy->pad_regs = devm_ioremap(&pdev->dev, res->start,
>>  					   resource_size(res));
>>  	if (!tegra_phy->pad_regs) {
>> @@ -1087,6 +1091,10 @@ static int tegra_usb_phy_probe(struct platform_device *pdev)
>>  		return  -ENXIO;
>>  	}
>>  
>> +	/*
>> +	 * Note that PHY and USB controller are using shared registers,
>> +	 * therefore devm_platform_ioremap_resource() can't be used here.
>> +	 */
>>  	tegra_phy->regs = devm_ioremap(&pdev->dev, res->start,
>>  				       resource_size(res));
>>  	if (!tegra_phy->regs) {
> 
> I'm not sure it's really going to stop *all* attempts. But at least for
> people that go through the trouble of reading the comments, yes, this
> should do the trick, so:
> 
> Acked-by: Thierry Reding <treding@...dia.com>

Will see, thanks :)