Am Montag, dem 21.06.2021 um 18:30 +0200 schrieb 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.
There are a lot of more writes with barriers to the controller slave interface in that function after clearing the FIFO. I don't see why this readback would be required. Regards, Lucas
