On Thu, Aug 07, 2014 at 04:51:18PM +0900, Inki Dae wrote: > On 2014년 08월 07일 15:58, Thierry Reding wrote: > > On Thu, Aug 07, 2014 at 02:09:19AM +0900, Inki Dae wrote: > >> 2014-08-06 16:43 GMT+09:00 Thierry Reding <thierry.reding@xxxxxxxxx>: [...] > >>> As far as I can tell non-continuous mode simply means that the host can > >>> turn off the HS clock after a high-speed transmission. I think Andrzej > >>> mentioned this already in another subthread, but this is an optional > >>> mode that peripherals can support if they have extra circuitry that > >>> provides an internal clock. Peripherals that don't have such circuitry > >>> may rely on the HS clock to perform in between transmissions and > >>> therefore require the HS clock to be always on (continuous mode). That's > >>> what the MIPI_DSI_CLOCK_NON_CONTINUOUS flag is: it advertises that the > >>> peripheral supports non-continuous mode and therefore the host can turn > >>> the HS clock off after high-speed transmissions. > >> > >> What I don't make sure is this sentence. With > >> MIPI_DSI_CLOCK_NON_CONTIUOUS flag, I guess two possible operations. > >> One is, > >> 1. host controller will generates signals if a bit of a register > >> related to non-contiguous clock mode is set or unset. > >> 2. And then video data is transmitted to panel in HS mode. > >> 3. And then D-PHY detects LP-11 signal (positive and negative lane all > >> are high). > >> 4. And then D-PHY disables HS clock of host controller. > >> 5. At this time, operation mode of host controller becomes LPM. > >> > >> Other is, > >> 1. host controller will generates signals if a bit of a register > >> related to non-contiguous clock mode is set or unset. > >> 2. And then D-PHY detects LP-11 signal (positive and negative lane all > >> are high). > >> 3. And then video data is transmitted to panel in LPM. > >> 4. At this time, operation mode of host controller becomes LPM. > >> > >> It seems that you says latter case. > > > > No. High speed clock and low power mode are orthogonal. Non-continuous > > mode simply means that the clock lane enters LP-11 between HS > > transmissions (see 5.6 "Clock Management" of the DSI specification). > > > > It seems that clock lane enters LP-11 regardless of HS clock enabled if > non-continous mode is used. Right? No, I think as long as HS clock is enabled the clock lane won't enter LP-11. Non-continuous mode means that the controller can disable the HS clock between HS transmissions. So in non-continuous mode the clock lane can enter LP-11 because the controller disables the HS clock. In continuous mode, then the clock will never be disabled, hence the clock lane will never enter LP-11. > And also it seems that non-continous mode is different from LPM at all > because with non-continuous mode, command data is transmitted to panel > in HS mode, but with LPM, command data is transmitted to panel in LP > mode. Also right? No. I think you can send command data to the peripheral in low power mode in both continuous and non-continuous clock modes. > If so, shouldn't the host driver disable HS clock, in case of LP mode, > before the host driver transmits command data? No. If the peripheral doesn't support non-continuous mode, then the HS clock must never be turned off. On the other hand, if the peripheral supports non-continuous mode, then the DSI host should automatically disable the HS clock between high-speed transmissions. That means if a packet is transmitted in low power mode the DSI host will not be transmitting in high-speed mode and therefore disable the HS clock. Obviously if the controller can't do that automatically then it might be necessary to explicitly do that in the driver. But I doubt that any DSI controller wouldn't be able to do that automatically. On Tegra we have a control bit that enables non-continuous mode: DSI_HS_CLK_CTRL: control for the HS clock lane - 0 = CONTINUOUS: HS clock is on all the time - 1 = TX_ONLY: HS clock is only active during HS transmissions > And it seems that only one of these two flags, MSG_LPM and NON-CONTINUOUS, > should be set by panel driver because with NON-CONTINUOUS clock mode, host > controller generate clock and data lane signals regardless of controlling > HS clock. No. Non-continuous mode is something that's specific to the peripheral and is always valid, whereas the MSG_LPM flag is only used to mark a packet to be transmitted in low power mode (as opposed to high speed mode). For peripherals that don't support non-continuous mode the NON_CONTINUOUS flag needs to be set. But the driver for the peripheral can still initiate low power mode packet transmissions by setting the MSG_LPM flag. Thierry
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