Re: [PATCH 2/2] drm/exynos: dsi: add LPM (Low Power Mode) transfer support

[Inki Dae <inki.dae@samsung.com>]

On 2014년 07월 24일 19:48, Andrzej Hajda wrote:
> +CC: Thierry and Alexandre
> 
> On 07/18/2014 12:56 PM, Inki Dae wrote:
>> This patch adds LPM transfer support for video or command data.
>>
>> With this patch, Exynos MIPI DSI controller can transfer command or
>> video data with HS or LP mode in accordance with mode_flags set
>> by LCD Panel driver.
>>
>> Signed-off-by: Inki Dae <inki.dae@samsung.com>
>> Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
>> ---
>>  drivers/gpu/drm/exynos/exynos_drm_dsi.c |   22 ++++++++++++++++++++--
>>  1 file changed, 20 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/exynos_drm_dsi.c b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>> index 2df3592..b120554 100644
>> --- a/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>> +++ b/drivers/gpu/drm/exynos/exynos_drm_dsi.c
>> @@ -426,13 +426,28 @@ static int exynos_dsi_enable_clock(struct exynos_dsi *dsi)
>>  			| DSIM_ESC_PRESCALER(esc_div)
>>  			| DSIM_LANE_ESC_CLK_EN_CLK
>>  			| DSIM_LANE_ESC_CLK_EN_DATA(BIT(dsi->lanes) - 1)
>> -			| DSIM_BYTE_CLK_SRC(0)
>> -			| DSIM_TX_REQUEST_HSCLK;
>> +			| DSIM_BYTE_CLK_SRC(0);
>> +
>> +	if (!(dsi->mode_flags & MIPI_DSI_MODE_CMD_LPM))
>> +		reg |= DSIM_TX_REQUEST_HSCLK;
>> +
> 
> Maybe I missed sth but it seems to me slightly unrelated to LPM flag.
> According to specs some panels can require this clock even in LPM mode.
> I wonder if recently introduced  MIPI_DSI_CLOCK_NON_CONTINUOUS wouldn't
> handle it.

It's different. MIPI DSI spec says,
"For continuous clock behaviour, the Clock Lane remains in high-speed
mode generating active clock signals between HS data packet
transmissions. For non-continuous clock behaviour, *the Clock Lane
enters the LP-11 state between HS data packet transmissions*."

> 
>>  	writel(reg, dsi->reg_base + DSIM_CLKCTRL_REG);
>>  
>>  	return 0;
>>  }
>>  
>> +static void exynos_dsi_enable_hs_clock(struct exynos_dsi *dsi,
>> +					bool enable)
>> +{
>> +	u32 reg = readl(dsi->reg_base + DSIM_CLKCTRL_REG);
>> +
>> +	reg &= ~DSIM_TX_REQUEST_HSCLK;
>> +	if (enable)
>> +		reg |= DSIM_TX_REQUEST_HSCLK;
>> +
>> +	writel(reg, dsi->reg_base + DSIM_CLKCTRL_REG);
>> +}
>> +
>>  static void exynos_dsi_disable_clock(struct exynos_dsi *dsi)
>>  {
>>  	u32 reg;
>> @@ -575,6 +590,9 @@ static void exynos_dsi_set_display_enable(struct exynos_dsi *dsi, bool enable)
>>  {
>>  	u32 reg;
>>  
>> +	if (!(dsi->mode_flags & MIPI_DSI_MODE_VIDEO_LPM))
>> +		exynos_dsi_enable_hs_clock(dsi, true);
>> +
> 
> It does not care about enable argument of the function, I guess it should.
> 

Yes, it's better to enable HS clock only in case of enabling. So will
add one more flag like below,

if (!(dsi->mode_flags & MIPI_DSI_MODE_VIDEO_LPM) && enable)

Thank,
Inki Dae

> Regards
> Andrzej
> 
>>  	reg = readl(dsi->reg_base + DSIM_MDRESOL_REG);
>>  	if (enable)
>>  		reg |= DSIM_MAIN_STAND_BY;
> 
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