[PATCH 4/4] drm/tidss: Fix sampling edge configuration

[Swamil Jain]

On 8/8/25 19:16, devarsh wrote:
> Hi Louis,
> 
> Thanks for the patch.
> 
> On 30/07/25 22:32, Louis Chauvet wrote:
>> As stated in the AM62x Technical Reference Manual (SPRUIV7B), the data
>> sampling edge needs to be configured in two distinct registers: one in the
>> TIDSS IP and another in the memory-mapped control register modules.
> 
> I don't think AM62x is thee only one which requires this and on the
> contrary not all SoCs require this extra setting. We had been waiting on
> confirmations from hardware team and very recently they gave a list of
> SoCs which require this, as per that I think we need to limit this to
> AM62x and AM62A per current supported SoCs.
> 
> Swamil,
> Please confirm on this and share if any additional details required here.
> 

Yeah Devarsh, as you mentioned, this is valid for AM62X, AM62A and 
AM62P. We would have upstreamed this feature, but there are some 
corrections in Technical Reference Manual for these SoCs regarding 
programming CTRL_MMR_DPI_CLK_CTRL register fields, we are in loop with 
H/W team, waiting for their official confirmation regarding this issue.

Thanks Louis for working on this patch, but we should wait for H/W 
team's confirmation.

Regards,
Swamil.

> Regards
> Devarsh
> 
>   Since
>> the latter is not within the same address range, a phandle to a syscon
>> device is used to access the regmap.
>>
>> Fixes: 32a1795f57ee ("drm/tidss: New driver for TI Keystone platform Display SubSystem")
>> Signed-off-by: Louis Chauvet <louis.chauvet at bootlin.com>
>>
>> ---
>>
>> Cc: stable at vger.kernel.org
>> ---
>>   drivers/gpu/drm/tidss/tidss_dispc.c | 14 ++++++++++++++
>>   1 file changed, 14 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c b/drivers/gpu/drm/tidss/tidss_dispc.c
>> index c0277fa36425ee1f966dccecf2b69a2d01794899..65ca7629a2e75437023bf58f8a1bddc24db5e3da 100644
>> --- a/drivers/gpu/drm/tidss/tidss_dispc.c
>> +++ b/drivers/gpu/drm/tidss/tidss_dispc.c
>> @@ -498,6 +498,7 @@ struct dispc_device {
>>   	const struct dispc_features *feat;
>>   
>>   	struct clk *fclk;
>> +	struct regmap *clk_ctrl;
>>   
>>   	bool is_enabled;
>>   
>> @@ -1267,6 +1268,11 @@ void dispc_vp_enable(struct dispc_device *dispc, u32 hw_videoport,
>>   		       FLD_VAL(mode->vdisplay - 1, 27, 16));
>>   
>>   	VP_REG_FLD_MOD(dispc, hw_videoport, DISPC_VP_CONTROL, 1, 0, 0);
>> +
>> +	if (dispc->clk_ctrl) {
>> +		regmap_update_bits(dispc->clk_ctrl, 0, 0x100, ipc ? 0x100 : 0x000);
>> +		regmap_update_bits(dispc->clk_ctrl, 0, 0x200, rf ? 0x200 : 0x000);
>> +	}
>>   }
>>   
>>   void dispc_vp_disable(struct dispc_device *dispc, u32 hw_videoport)
>> @@ -3012,6 +3018,14 @@ int dispc_init(struct tidss_device *tidss)
>>   
>>   	dispc_init_errata(dispc);
>>   
>> +	dispc->clk_ctrl = syscon_regmap_lookup_by_phandle_optional(tidss->dev->of_node,
>> +								   "ti,clk-ctrl");
>> +	if (IS_ERR(dispc->clk_ctrl)) {
>> +		r = dev_err_probe(dispc->dev, PTR_ERR(dispc->clk_ctrl),
>> +				  "DISPC: syscon_regmap_lookup_by_phandle failed.\n");
>> +		return r;
>> +	}
>> +
>>   	dispc->fourccs = devm_kcalloc(dev, ARRAY_SIZE(dispc_color_formats),
>>   				      sizeof(*dispc->fourccs), GFP_KERNEL);
>>   	if (!dispc->fourccs)
>>
>