[v1] usb: phy: tegra: Add clarifying comments about the shared registers
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Message ID 20200202224259.29187-1-digetx@gmail.com
State New
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  • [v1] usb: phy: tegra: Add clarifying comments about the shared registers
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Commit Message

Dmitry Osipenko Feb. 2, 2020, 10:42 p.m. UTC
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@gmail.com>
---
 drivers/usb/phy/phy-tegra-usb.c | 8 ++++++++
 1 file changed, 8 insertions(+)

Comments

Thierry Reding Feb. 3, 2020, 11:28 a.m. UTC | #1
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@gmail.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@nvidia.com>
Dmitry Osipenko Feb. 3, 2020, 4:26 p.m. UTC | #2
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@gmail.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@nvidia.com>

Will see, thanks :)

Patch
diff mbox series

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) {