Re: [PATCH V3 08/19] soc: tegra: pmc: Clean-up PMC helper functions

[Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 17/07/15 11:25, Thierry Reding wrote:
> * PGP Signed by an unknown key
> 
> On Mon, Jul 13, 2015 at 01:39:46PM +0100, Jon Hunter wrote:
>> The following clean-ups have been made to the PMC code:
>>
>> 1. Add a macro for determining the state of a PMC powergate
>> 2. Use the readx_poll_timeout() function instead of implementing a local
>>    polling loop with a timeout.
>> 3. Use a case-statement in the function that removes the powergate clamp
>>    instead of multiple if-statements to improve readability.
>>
>> Signed-off-by: Jon Hunter <jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
>> ---
>>  drivers/soc/tegra/pmc.c | 72 ++++++++++++++++++++++++-------------------------
>>  1 file changed, 35 insertions(+), 37 deletions(-)
>>
>> diff --git a/drivers/soc/tegra/pmc.c b/drivers/soc/tegra/pmc.c
>> index c0635bdd4ee3..180d434deec5 100644
>> --- a/drivers/soc/tegra/pmc.c
>> +++ b/drivers/soc/tegra/pmc.c
>> @@ -28,6 +28,7 @@
>>  #include <linux/export.h>
>>  #include <linux/init.h>
>>  #include <linux/io.h>
>> +#include <linux/iopoll.h>
>>  #include <linux/of.h>
>>  #include <linux/of_address.h>
>>  #include <linux/platform_device.h>
>> @@ -56,6 +57,8 @@
>>  #define  PWRGATE_TOGGLE_START		(1 << 8)
>>  
>>  #define REMOVE_CLAMPING			0x34
>> +#define  REMOVE_CLAMPING_VDEC		(1 << 3)
>> +#define  REMOVE_CLAMPING_PCIE		(1 << 4)
>>  
>>  #define PWRGATE_STATUS			0x38
>>  
>> @@ -101,6 +104,8 @@
>>  
>>  #define GPU_RG_CNTRL			0x2d4
>>  
>> +#define PMC_PWRGATE_STATE(val, id)	(!!(val & BIT(id)))
> 
> I find double-negations very difficult to read. ((value & BIT(id)) != 0)
> is clearer in my opinion. Also I'd suggest status or value as the first
> parameter name, for consistency with other parts of the driver.
> 
>> +
>>  struct tegra_pmc_soc {
>>  	unsigned int num_powergates;
>>  	const char *const *powergates;
>> @@ -177,15 +182,14 @@ static void tegra_pmc_writel(u32 value, unsigned long offset)
>>   */
>>  static int tegra_powergate_set(int id, bool new_state, bool wait)
>>  {
>> -	unsigned long timeout;
>> -	bool status;
>>  	int ret = 0;
>> +	u32 val;
>>  
>>  	mutex_lock(&pmc->powergates_lock);
>>  
>> -	status = tegra_pmc_readl(PWRGATE_STATUS) & (1 << id);
>> +	val = tegra_pmc_readl(PWRGATE_STATUS);
>>  
>> -	if (status == new_state) {
>> +	if (PMC_PWRGATE_STATE(val, id) == new_state) {
>>  		mutex_unlock(&pmc->powergates_lock);
>>  		return 0;
>>  	}
>> @@ -193,17 +197,9 @@ static int tegra_powergate_set(int id, bool new_state, bool wait)
>>  	tegra_pmc_writel(PWRGATE_TOGGLE_START | id, PWRGATE_TOGGLE);
>>  
>>  	if (wait) {
>> -		timeout = jiffies + msecs_to_jiffies(100);
>> -		ret = -ETIMEDOUT;
>> -
>> -		while (time_before(jiffies, timeout)) {
>> -			status = !!(tegra_pmc_readl(PWRGATE_STATUS) & BIT(id));
>> -			if (status == new_state) {
>> -				ret = 0;
>> -				break;
>> -			}
>> -			udelay(10);
>> -		}
>> +		ret = readx_poll_timeout(tegra_pmc_readl, PWRGATE_STATUS,
>> +				val, PMC_PWRGATE_STATE(val, id) == new_state,
>> +				10, 100000);
>>  	}
>>  
>>  	mutex_unlock(&pmc->powergates_lock);
>> @@ -242,13 +238,10 @@ EXPORT_SYMBOL(tegra_powergate_power_off);
>>   */
>>  int tegra_powergate_is_powered(int id)
>>  {
>> -	u32 status;
>> -
>>  	if (!pmc->soc || id < 0 || id >= pmc->soc->num_powergates)
>>  		return -EINVAL;
>>  
>> -	status = tegra_pmc_readl(PWRGATE_STATUS) & (1 << id);
>> -	return !!status;
>> +	return PMC_PWRGATE_STATE(tegra_pmc_readl(PWRGATE_STATUS), id);
> 
> I'd prefer to keep the two steps here. As a general rule I try never to
> mix reading or writing a register with other code on the same line.
> 
>>  }
>>  
>>  /**
>> @@ -257,34 +250,39 @@ int tegra_powergate_is_powered(int id)
>>   */
>>  int tegra_powergate_remove_clamping(int id)
>>  {
>> -	u32 mask;
>> +	u32 val, reg;
> 
> Side note: Please use value instead of val since that's the form used
> elsewhere in the driver. Also reg would be more appropriately called
> offset or similar because that's what it really is. It would also be
> more naturally an unsized type, such as unsigned int. But...
> 
>>  
>>  	if (!pmc->soc || id < 0 || id >= pmc->soc->num_powergates)
>>  		return -EINVAL;
>>  
>>  	/*
>> -	 * On Tegra124 and later, the clamps for the GPU are controlled by a
>> -	 * separate register (with different semantics).
>> +	 * In most cases the bit for removing the IO clamping is the same as
>> +	 * the powergate partition ID, however, this is not always the case.
>> +	 * Furthermore, on Tegra124 and later, the clamps for the GPU are
>> +	 * controlled by a separate register (with different semantics). The
>> +	 * following case-statement handles these exceptions.
>>  	 */
>> -	if (id == TEGRA_POWERGATE_3D) {
>> +	val = 1 << id;
>> +	reg = REMOVE_CLAMPING;
>> +
>> +	switch (id) {
>> +	case TEGRA_POWERGATE_3D:
>>  		if (pmc->soc->has_gpu_clamps) {
>> -			tegra_pmc_writel(0, GPU_RG_CNTRL);
>> -			return 0;
>> +			val = 0;
>> +			reg  = GPU_RG_CNTRL;
>>  		}
>> +		break;
>> +	case TEGRA_POWERGATE_VDEC:
>> +		val = REMOVE_CLAMPING_VDEC;
>> +		break;
>> +	case TEGRA_POWERGATE_PCIE:
>> +		val = REMOVE_CLAMPING_PCIE;
>> +		break;
>> +	default:
>> +		break;
>>  	}
>>  
>> -	/*
>> -	 * Tegra 2 has a bug where PCIE and VDE clamping masks are
>> -	 * swapped relatively to the partition ids
>> -	 */
>> -	if (id == TEGRA_POWERGATE_VDEC)
>> -		mask = (1 << TEGRA_POWERGATE_PCIE);
>> -	else if (id == TEGRA_POWERGATE_PCIE)
>> -		mask = (1 << TEGRA_POWERGATE_VDEC);
>> -	else
>> -		mask = (1 << id);
>> -
>> -	tegra_pmc_writel(mask, REMOVE_CLAMPING);
>> +	tegra_pmc_writel(val, reg);
> 
> ... to be honest, I think the previous code was more straightforward, so
> I'd prefer if you dropped this particular hunk.

Ok, I will drop that part. Jon