[PATCH v2 1/2] drm/mipi-dsi: add (LPM) Low Power Mode transfer support
Inki Dae
inki.dae at samsung.com
Mon Aug 11 01:01:56 PDT 2014
On 2014년 08월 11일 16:44, Andrzej Hajda wrote:
> On 08/11/2014 09:09 AM, Inki Dae wrote:
>> On 2014년 08월 08일 18:40, Andrzej Hajda wrote:
>>> On 08/08/2014 11:02 AM, Andrzej Hajda wrote:
>>>> On 08/08/2014 09:37 AM, Inki Dae wrote:
>>>>> On 2014년 08월 08일 16:03, Thierry Reding wrote:
>>>>>> On Fri, Aug 08, 2014 at 10:45:47AM +0900, Inki Dae wrote:
>>>>>>> On 2014년 08월 07일 22:55, Thierry Reding wrote:
>>>>>>>> On Thu, Aug 07, 2014 at 10:39:29PM +0900, Inki Dae wrote:
>>>>>>>>> On 2014년 08월 07일 22:17, Thierry Reding wrote:
>>>>>>>>>> On Thu, Aug 07, 2014 at 10:05:44PM +0900, Inki Dae wrote:
>>>>>>>>>>> On 2014년 08월 07일 20:09, Thierry Reding wrote:
>>>>>>>>>>>> On Thu, Aug 07, 2014 at 07:49:03PM +0900, Inki Dae wrote:
>>>>>>>>>>>>> On 2014년 08월 07일 18:09, Thierry Reding wrote:
>>>>>>>>>>>>>> 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 at gmail.com>:
>>>>>>>>>>>>>> [...]
>>>>>>>>>>>>>>>>>> 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.
>>>>>>>>>>>>> It makes me a little bit confusing. You said "if HS clock is enabled,
>>>>>>>>>>>>> the the clock lane won't enter LP-11" But you said again "the clock lane
>>>>>>>>>>>>> can enter LP-11 because the controller disables the HS clock" What is
>>>>>>>>>>>>> the meaning?
>>>>>>>>>>>> It means that if the HS clock is enabled, then the clock lane is not in
>>>>>>>>>>>> LP-11. When the HS clock stops, then the clock lane enters LP-11.
>>>>>>>>>>>>
>>>>>>>>>>>>>> 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.
>>>>>>>>>>>>> What is LPM you think? I thought LPM is LP-11 and HS clock disabled. So
>>>>>>>>>>>>> for LPM transfer, lanes should be LP-11 state and also HS clock of the
>>>>>>>>>>>>> host controller should be disabled.
>>>>>>>>>>>> No. I don't think any transmissions can happen when all lanes are in
>>>>>>>>>>>> LP-11 state. The MIPI_DSI_MSG_USE_LPM is used to specify that a packet
>>>>>>>>>>>> should be transmitted in low power mode (see LP Transmission in 2.1
>>>>>>>>>>>> "Definitions" of the MIPI DSI specification).
>>>>>>>>>>>>
>>>>>>>>>>> Hm.. I see. I meant,
>>>>>>>>>>>
>>>>>>>>>>> if (flags & MIPI_DSI_MSG_USE_LPM)
>>>>>>>>>>> disable HS clock <- required.
>>>>>>>>>>>
>>>>>>>>>>> transmit command data <- in LPM.
>>>>>>>>>> No. Disabling the HS clock is not required for LPM mode. In fact if the
>>>>>>>>>> peripheral specifies that it doesn't support non-continuous mode then
>>>>>>>>>> the HS clock must *never* be disabled as long as the peripheral is in
>>>>>>>>>> use.
>>>>>>>>>>
>>>>>>>>>> MIPI_DSI_MSG_USE_LPM and MIPI_DSI_CLOCK_NON_CONTINUOUS are unrelated and
>>>>>>>>>> need to be considered separately.
>>>>>>>>> I mentioned already LPM and NON_CONTINUOUS are unrelated.
>>>>>>>>>
>>>>>>>>> It seems that you say the only way to transfer command data in LPM is
>>>>>>>>> non-continuous clock mode.
>>>>>>>> No, that's not what I'm saying.
>>>>>>>>
>>>>>>>>> However, you said and also the spec says, "Non-continuous mode simply
>>>>>>>>> means that the clock lane enters LP-11 between HS transmissions".
>>>>>>>>> Doesn't *between HS transmissions" mean the command data is transmitted
>>>>>>>>> in HS, *not in LPM*, and clock lane enters LP-11 between them?
>>>>>>>> Not necessarily. You can transmit command packets in high-speed mode,
>>>>>>>> but you don't have to. If you transmit packets in low power mode, then
>>>>>>> That would may why we are mentioning same comments repeatedly.
>>>>>>>
>>>>>>> In my case, host driver waits for the lane stop state (LP-11), and then
>>>>>>> disables HS clock to transmit command data in LPM. Of course, I'm not
>>>>>>> sure that yet it's correct way.
>>>>>> That's confusing. How can the lane go to LP-11 when the clock is still
>>>>>> running?
>>>>> Actually, we are doing so. If the clock is still running then dsi driver
>>>>> will wait for stop state of the clock and data lanes. Know that this is
>>>>> valid only when initial time - just one time since power up.
>>>>>
>>>>> /* Check clock and data lane state are stop state */
>>>>> timeout = 100;
>>>>> do {
>>>>> if (timeout-- == 0) {
>>>>> dev_err(dsi->dev, "waiting for bus lanes timed out\n");
>>>>> return -EFAULT;
>>>>> }
>>>>>
>>>>> reg = readl(dsi->reg_base + DSIM_STATUS_REG);
>>>>> if ((reg & DSIM_STOP_STATE_DAT(lanes_mask))
>>>>> != DSIM_STOP_STATE_DAT(lanes_mask))
>>>>> continue;
>>>>> } while (!(reg & (DSIM_STOP_STATE_CLK | DSIM_TX_READY_HS_CLK)));
>>>> This is only in initialization phase of DSI. 'If' inside the loop is
>>>> quite clear
>>>> - it checks for LP11 on all requested data lanes. 'while' check is
>>>> little bit suspicious.
>>>> It seems to be only for non-continuous clock behavior, on the other side
>>>> it is according to guidelines
>>>> in specs.
>>> After reviewing it again 'while' check looks OK :), sorry for noise.
>>> Loop exits w/o timeout either HS_CLK is ready (continuous clock
>>> behavior) either HS_CLK is stopped (non-continuous clock behavior).
>>>
>>> Regards
>>> Andrzej
>>>
>>>> Inki, have you tried to take an assumption your panel requires
>>>> continuous clock behavior and exynos
>>>> dsi driver currently supports only non-continuous clock behavior, so it
>>>> needs some fixes to make it work.
>> I'm not sure yet. All I can say is that the panel works well only with
>> clearing DSIM_TX_REQUEST_HSCLK and DSIM_CMD_LPDT_LP.
>
> I have performed simple test: I have enabled/disabled DSIM_TX_REQUEST_HSCLK
> and tested DSIM_STOP_STATE_CLK | DSIM_TX_READY_HS_CLK bits at the end
> of the initialization. The result:
> a) DSIM_TX_REQUEST_HSCLK == 0 => DSIM_TX_READY_HS_CLK set
> b) DSIM_TX_REQUEST_HSCLK == 1 => DSIM_STOP_STATE_CLK set
>
> It clearly indicates that DSIM_TX_REQUEST_HSCLK is equivalent of
> non-continuous clock behavior.
> So your panel requires continuous clock behavior(DSIM_TX_REQUEST_HSCLK
> == 0).
>
> Regarding DSIM_CMD_LPDT_LP you wrote it should be cleared in case of
> your panel. It means
> you need HS mode transfer.
As a result, it doesn't work. there would be our missing something.
I'll let me know how to test it by private email.
Thanks,
Inki Dae
>
> Regards
> Andrzej
>
>> And more thing, we need to check that disabling these two flags means
>> non-continuous clock mode or just low power transfer.
>> I think these two flags all should be also disabled in case peripheral
>> doesn't support non-continuous clock but want to transmit data in low power.
>> In this case, what should we call this mode?
>>
>>>> Exynos specs are very unclear on the subject so it is hard to guess how
>>>> the registers should be configured
>> For this, Youngjun are trying to contact HW guys.
>>
>> Thanks,
>> Inki Dae
>>
>>>> to have continuous/non-continuous clock behavior.
>>>>
>>>> Regards
>>>> Andrzej
>>>>
>>>>>>> In Tegra, What to do for it?
>>>>>> There are two bits in two separate registers for this:
>>>>>>
>>>>>> DSI_HOST_CONTROL:
>>>>>> bit 5: DSI_HIGH_SPEED_TRANS: DSI high speed transmission of
>>>>>> packets
>>>>>> - 0 = LOW: low speed
>>>>>> - 1 = HIGH: high speed
>>>>>>
>>>>>> DSI_CONTROL:
>>>>>> bit 20: 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
>>>>>>
>>>>>> So if the peripheral supports non-continuous mode of operation we set
>>>>>> the DSI_HS_CLK_CTRL bit, otherwise we clear it to make sure the clock
>>>>>> remains on all the time.
>>>>>>
>>>>>> When a packet is to be transmitted in high speed mode, we set the
>>>>>> DSI_HIGH_SPEED_TRANS bit. For low power mode transmissions that bit is
>>>>>> cleared.
>>>>> That is exactly what I want. In your case, if you want to transmit
>>>>> command data in Low Power Mode in case of supporting non-continuous
>>>>> clock mode, then you would set DSI_HS_CLK_CTRL (TX_ONLY), and also you
>>>>> would clear DSI_HIGH_SPEED_TRANS (LOW).
>>>>>
>>>>> So I guess,
>>>>>
>>>>> if (flags & MIPI_DSI_MODE_NON_CONTINUOUS) {
>>>>> disable DSI_HIGH_SPEED_TRANS; <- LOW
>>>>> enable DSI_HS_CLK_CTRL; <- TX_ONLY
>>>>> }
>>>>>
>>>>> transmit command data <- in LPM.
>>>>>
>>>>> However, what if the peripheral doesn't support non-continuous but want
>>>>> to transmit command data in LPM? Is that impossible?
>>>>>
>>>>> Thanks,
>>>>> Inki Dae
>>>>>
>>>>>> Thierry
>>>>>>
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