diff mbox series

ati-vga: Clarify comment (to be squashed in previous patch)

Message ID 20190620195213.C54127461AE@zero.eik.bme.hu
State New
Headers show
Series ati-vga: Clarify comment (to be squashed in previous patch) | expand

Commit Message

BALATON Zoltan June 20, 2019, 7:46 p.m. UTC 
Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/ati.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/hw/display/ati.c b/hw/display/ati.c
index 6fbdda288f..932a1eacea 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -538,9 +538,14 @@  static void ati_mm_write(void *opaque, hwaddr addr,
     case GPIO_MONID ... GPIO_MONID + 3:
         /* FIXME What does Radeon have here? */
         if (s->dev_id == PCI_DEVICE_ID_ATI_RAGE128_PF) {
-            /* Rage128p accesses DDC used to get EDID on these pins */
             ati_reg_write_offs(&s->regs.gpio_monid,
                                addr - GPIO_MONID, data, size);
+            /*
+             * Rage128p accesses DDC used to get EDID via these bits.
+             * Only touch i2c when write overlaps 3rd byte because some
+             * drivers access this reg via multiple partial writes and
+             * without this spurious bits would be sent.
+             */
             if ((s->regs.gpio_monid & BIT(25)) &&
                 addr <= GPIO_MONID + 2 && addr + size > GPIO_MONID + 2) {
                 s->regs.gpio_monid = ati_i2c(s->bbi2c, s->regs.gpio_monid, 1);