[PATCH] drm: mxsfb: Clear FIFO_CLEAR bit

[Marek Vasut]

On 6/21/21 2:14 PM, Lucas Stach wrote:

[...]

>> diff --git a/drivers/gpu/drm/mxsfb/mxsfb_kms.c b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>> index 98d8ba0bae84..22cb749fc9bc 100644
>> --- a/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>> +++ b/drivers/gpu/drm/mxsfb/mxsfb_kms.c
>> @@ -241,6 +241,9 @@ static void mxsfb_crtc_mode_set_nofb(struct mxsfb_drm_private *mxsfb,
>>   
>>   	/* Clear the FIFOs */
>>   	writel(CTRL1_FIFO_CLEAR, mxsfb->base + LCDC_CTRL1 + REG_SET);
>> +	readl(mxsfb->base + LCDC_CTRL1);
> 
> Do you really need those readbacks? As both writes are targeting the
> same slave interface, the memory barrier in the clear write should push
> the set write.

What would push the clear write then ? We can drop one of the readl()s, 
but not the last one.