[PATCH 3/6] drm: rcar-du: Fix LVDS stop sequence

[Tomi Valkeinen]

On 18/01/2023 23:12, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Tue, Jan 17, 2023 at 03:51:51PM +0200, Tomi Valkeinen wrote:
>> From: Koji Matsuoka <koji.matsuoka.xm at renesas.com>
>>
>> According to H/W manual, LVDCR0 register must be cleared bit by bit when
> 
> s at H/W at the hardware/
> 
>> disabling LVDS.
> 
> I don't like this much, but I think I'll stop fighting :-)
> 
>> Signed-off-by: Koji Matsuoka <koji.matsuoka.xm at renesas.com>
>> Signed-off-by: LUU HOAI <hoai.luu.ub at renesas.com>
>> [tomi.valkeinen: simplified the code a bit]
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen+renesas at ideasonboard.com>
>> ---
>>   drivers/gpu/drm/rcar-du/rcar_lvds.c | 27 ++++++++++++++++++++++++++-
>>   1 file changed, 26 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/rcar-du/rcar_lvds.c b/drivers/gpu/drm/rcar-du/rcar_lvds.c
>> index 674b727cdaa2..01800cef1c33 100644
>> --- a/drivers/gpu/drm/rcar-du/rcar_lvds.c
>> +++ b/drivers/gpu/drm/rcar-du/rcar_lvds.c
>> @@ -87,6 +87,11 @@ static void rcar_lvds_write(struct rcar_lvds *lvds, u32 reg, u32 data)
>>   	iowrite32(data, lvds->mmio + reg);
>>   }
>>   
>> +static u32 rcar_lvds_read(struct rcar_lvds *lvds, u32 reg)
>> +{
>> +	return ioread32(lvds->mmio + reg);
>> +}
> 
> Could you please move read before write ?

Sure.

>> +
>>   /* -----------------------------------------------------------------------------
>>    * PLL Setup
>>    */
>> @@ -549,8 +554,28 @@ static void rcar_lvds_atomic_disable(struct drm_bridge *bridge,
>>   				     struct drm_bridge_state *old_bridge_state)
>>   {
>>   	struct rcar_lvds *lvds = bridge_to_rcar_lvds(bridge);
>> +	u32 lvdcr0;
>> +
>> +	lvdcr0 = rcar_lvds_read(lvds, LVDCR0);
>> +
>> +	lvdcr0 &= ~LVDCR0_LVRES;
>> +	rcar_lvds_write(lvds, LVDCR0, lvdcr0);
>> +
>> +	if (lvds->info->quirks & RCAR_LVDS_QUIRK_GEN3_LVEN) {
>> +		lvdcr0 &= ~LVDCR0_LVEN;
>> +		rcar_lvds_write(lvds, LVDCR0, lvdcr0);
>> +	}
>> +
>> +	if (lvds->info->quirks & RCAR_LVDS_QUIRK_PWD) {
>> +		lvdcr0 &= ~LVDCR0_PWD;
>> +		rcar_lvds_write(lvds, LVDCR0, lvdcr0);
>> +	}
>> +
>> +	if (!(lvds->info->quirks & RCAR_LVDS_QUIRK_EXT_PLL)) {
>> +		lvdcr0 &= ~LVDCR0_PLLON;
>> +		rcar_lvds_write(lvds, LVDCR0, lvdcr0);
>> +	}
> 
> This will leave LVDCR0_BEN and LVDCR0_LVEN on Gen2. Is that fine ?

I don't know, I don't have the manuals or HW. But your point is a bit 
worrying.

I think we can just do a rcar_lvds_write(lvds, LVDCR0, 0) after the 
above shenanigans, to make sure everything is disabled. The HW manual 
doesn't tell us to do that, though, on gen3. Do you think that will be a 
problem?

And I'm not fully serious with the last sentence...

  Tomi