On 13/04/16 10:00, Laxman Dewangan wrote: > > On Wednesday 13 April 2016 02:17 PM, Jon Hunter wrote: >> On 12/04/16 15:56, Laxman Dewangan wrote: >>> NVIDIA Tegra210 supports some of the IO interface which can operate >>> at 1.8V or 3.3V I/O rail voltage levels. SW needs to configure >>> Tegra PMC register to set different voltage level of IO interface based >>> on IO rail voltage from power supply i.e. power regulators. >>> >>> Add APIs to set and get IO rail voltage from the client driver. >> I think that we need some further explanation about the scenario when >> this is used. In other words, why this configuration needs to be done in >> the kernel versus the bootloader. Is this something that can change at >> runtime? I could see that for SD cards it may. > > Yes, SDIO3.0 support needs dynamic IO rail voltage change and so pad > voltage change. > >>> #define GPU_RG_CNTRL 0x2d4 >>> +static DEFINE_SPINLOCK(tegra_pmc_access_lock); >>> + >> We already have a mutex for managing concurrent accesses, do we need >> this? > Mutex is sleeping calls and we really dont need this. This is sleep for > small duration and we should do this in spinlock. Yes but do you need to call it from a interrupt context? It seems that these are not called very often, may be on boot, or when swapping an SD card, and so although a spinlock would be faster, the overhead of the mutex would be negligible in this case. I think that you need to justify why this needs to be a spinlock with a use-case that requires it. >>> + >>> +static struct tegra_io_rail_voltage_bit_info >>> tegra210_io_rail_voltage_info[] = { >>> + TEGRA_IO_RAIL_VOLTAGE(SDMMC1, 12), >>> + TEGRA_IO_RAIL_VOLTAGE(SDMMC3, 13), >>> + TEGRA_IO_RAIL_VOLTAGE(AUDIO_HV, 18), >>> + TEGRA_IO_RAIL_VOLTAGE(DMIC, 20), >>> + TEGRA_IO_RAIL_VOLTAGE(GPIO, 21), >>> + TEGRA_IO_RAIL_VOLTAGE(SPI_HV, 23), >>> +}; >>> + >> You could simply this by having a look-up table similar to what we do >> for the powergates. > Revising the power gate code, it needs ID matches with bit location but > it is not the case here. We need to have lookup from ID to bit position. I still don't see why you could not have ... static unsigned int tegra210_io_rail_voltage_bit[] = { [TEGRA_IO_RAIL_SDMMC1] = 12, ... } You could avoid the for-loop in the lookup as well as all the extra definitions. Seems a lot simpler. > >> >>> static u32 tegra_pmc_readl(unsigned long offset) >>> { >>> return readl(pmc->base + offset); >>> @@ -175,6 +202,16 @@ static void tegra_pmc_writel(u32 value, unsigned >>> long offset) >>> writel(value, pmc->base + offset); >>> } >>> +static void _tegra_pmc_register_update(unsigned long addr, >>> unsigned long mask, >>> + unsigned long val) >> u32 for mask and val. May be consider renaming to tegra_pmc_rmw(). > > update is common from the other framework like regmap so it is here. > > >> >>> +static int tegra_io_rail_voltage_get_bit_pos(int io_rail_id) >> All the tegra_io_rail_xxx() APIs just use "id" and it is an unsigned >> int. Any reason this needs to be an int? We should keep the naming and >> type consistent. > > OK, will do. > >>> + >>> +int tegra_io_rail_voltage_set(int io_rail, int val) >> Same here w.r.t "io_rail". >> >> Also it appears that "val" should only be 0 or 1 but we don't check for >> this. I see that you treat all non-zero values as '1' but that seems a >> bit funny. You may consider having the user pass uV and then you could >> check for either 3300000 or 1800000. > > What about enums then? > May be we can use the DT binding header here. Seems better just to specify the voltage in uV in the DT and pass it to this function. >> >>> + >>> + spin_lock_irqsave(&tegra_pmc_access_lock, flags); >>> + _tegra_pmc_register_update(PMC_PWR_DET, mask, mask); >>> + _tegra_pmc_register_update(PMC_PWR_DET_VAL, mask, bval); >> Hmmm ... this does not appear to be consistent with the TRM. It says to >> write to the PMC_PWR_DET register and then the PMC_PWR_LATCH register. I >> see in the Tegra210 TRM it says to only write the to ONLY the >> PMC_PWR_DET_VAL register in other places. The TRM appears to be quite >> confusing here, can you explain this? > > The TRM needs to be update. There is no LATCH register in the T210. > PMC_PWR_DET and PMC_PWR_DET_VAL are registers for this. I have internal > tracking bug for correcting this. Why do you need to program both? I think that we should be clear here about the procedure. If the TRM is wrong, then there should be at least a comment here describing the correct sequence. Cheers Jon -- To unsubscribe from this list: send the line "unsubscribe linux-gpio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html