On Fri, 20 May 2022, Ville Syrjälä ville.syrjala@linux.intel.com wrote:

On Fri, May 20, 2022 at 12:46:00PM +0300, Jani Nikula wrote:

...

The VBT send packet port selection was never updated for ICL+ where the 2nd link is on port B instead of port C as in VLV+ DSI.

First, single link DSI needs to use the configured port instead of relying on the VBT sequence block port. Remove the hard-coded port C check here and make it generic. For reference, see commit f915084edc5a ("drm/i915: Changes related to the sequence port no for") for the original VLV specific fix.

Second, the sequence block port number is either 0 or 1, where 1 indicates the 2nd link. Remove the hard-coded port C here for 2nd link. (This could be a "find second set bit" on DSI ports, but just check the two possible options.)

Third, sanity check the result with a warning to avoid a NULL pointer dereference.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5984 Cc: stable@vger.kernel.org # v4.19+ Cc: Ville Syrjala ville.syrjala@linux.intel.com Signed-off-by: Jani Nikula jani.nikula@intel.com

---

drivers/gpu/drm/i915/display/intel_dsi_vbt.c | 33 +++++++++++++------- 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c index f370e9c4350d..dd24aef925f2 100644 --- a/drivers/gpu/drm/i915/display/intel_dsi_vbt.c +++ b/drivers/gpu/drm/i915/display/intel_dsi_vbt.c @@ -125,9 +125,25 @@ struct i2c_adapter_lookup { #define ICL_GPIO_DDPA_CTRLCLK_2 8 #define ICL_GPIO_DDPA_CTRLDATA_2 9 -static enum port intel_dsi_seq_port_to_port(u8 port) +static enum port intel_dsi_seq_port_to_port(struct intel_dsi *intel_dsi,

• 			    u8 seq_port)
  

{

• return port ? PORT_C : PORT_A;

• /*

• * If single link DSI is being used on any port, the VBT sequence block
  

• * send packet apparently always has 0 for the port. Just use the port
  

• * we have configured, and ignore the sequence block port.
  

• */
  

• if (hweight8(intel_dsi->ports) == 1)

• return ffs(intel_dsi->ports) - 1;
  

• if (seq_port) {

• if (intel_dsi->ports & PORT_B)
  

• 	return PORT_B;
  

• else if (intel_dsi->ports & PORT_C)
  

• 	return PORT_C;
  

• }
• return PORT_A;

Hmm. I guess a bit more generic way to express that could be to just pick the Nth set bit from intel_dsi->ports, where N==seq_port. Assuming seq_port is just an index. But I guess we're not really expecting to grow more DSI ports any time soon, so this seems sufficient for the current situation.

Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com

Thanks, pushed to drm-intel-next.

BR, Jani.

...

} static const u8 *mipi_exec_send_packet(struct intel_dsi *intel_dsi, @@ -149,15 +165,10 @@ static const u8 *mipi_exec_send_packet(struct intel_dsi *intel_dsi, seq_port = (flags >> MIPI_PORT_SHIFT) & 3;

• /* For DSI single link on Port A & C, the seq_port value which is

• * parsed from Sequence Block#53 of VBT has been set to 0
  

• * Now, read/write of packets for the DSI single link on Port A and
  

• * Port C will based on the DVO port from VBT block 2.
  

• */
  

• if (intel_dsi->ports == (1 << PORT_C))

• port = PORT_C;
  

• else

• port = intel_dsi_seq_port_to_port(seq_port);
  

• port = intel_dsi_seq_port_to_port(intel_dsi, seq_port);
• if (drm_WARN_ON(&dev_priv->drm, !intel_dsi->dsi_hosts[port]))

• goto out;
  

dsi_device = intel_dsi->dsi_hosts[port]->device; if (!dsi_device) { -- 2.30.2