On Mon, Sep 16, 2019 at 01:32:58PM +0200, Enric Balletbo i Serra wrote: > Hi, > > On 16/9/19 12:49, Laurent Pinchart wrote: > > Hi Brian, > > > > On Mon, Sep 16, 2019 at 06:36:14AM -0400, Brian Masney wrote: > >> On Mon, Sep 16, 2019 at 12:02:09PM +0200, Andrzej Hajda wrote: > >>> On 15.08.2019 02:48, Brian Masney wrote: > >>>> When attempting to configure this driver on a Nexus 5 phone (msm8974), > >>>> setting up the dummy i2c bus for TX_P0 would fail due to an -EBUSY > >>>> error. The downstream MSM kernel sources [1] shows that the proper value > >>>> for TX_P0 is 0x78, not 0x70, so correct the value to allow device > >>>> probing to succeed. > >>>> > >>>> [1] https://github.com/AICP/kernel_lge_hammerhead/blob/n7.1/drivers/video/slimport/slimport_tx_reg.h > >>>> > >>>> Signed-off-by: Brian Masney <masneyb@xxxxxxxxxxxxx> > >>>> --- > >>>> drivers/gpu/drm/bridge/analogix-anx78xx.h | 2 +- > >>>> 1 file changed, 1 insertion(+), 1 deletion(-) > >>>> > >>>> diff --git a/drivers/gpu/drm/bridge/analogix-anx78xx.h b/drivers/gpu/drm/bridge/analogix-anx78xx.h > >>>> index 25e063bcecbc..bc511fc605c9 100644 > >>>> --- a/drivers/gpu/drm/bridge/analogix-anx78xx.h > >>>> +++ b/drivers/gpu/drm/bridge/analogix-anx78xx.h > >>>> @@ -6,7 +6,7 @@ > >>>> #ifndef __ANX78xx_H > >>>> #define __ANX78xx_H > >>>> > >>>> -#define TX_P0 0x70 > >>>> +#define TX_P0 0x78 > >>> > >>> > >>> This bothers me little. There are no upstream users, grepping android > >>> sources suggests that both values can be used [1][2] (grep for "#define > >>> TX_P0"), moreover there is code suggesting both values can be valid [3]. > >>> > >>> Could you verify datasheet which i2c slave addresses are valid for this > >>> chip, if both I guess this patch should be reworked. > >>> > >>> > >>> [1]: > >>> https://android.googlesource.com/kernel/msm/+/android-msm-flo-3.4-jb-mr2/drivers/misc/slimport_anx7808/slimport_tx_reg.h > >>> > >>> [2]: > >>> https://github.com/AndroidGX/SimpleGX-MM-6.0_H815_20d/blob/master/drivers/video/slimport/anx7812/slimport7812_tx_reg.h > >>> > >>> [3]: > >>> https://github.com/commaai/android_kernel_leeco_msm8996/blob/master/drivers/video/msm/mdss/dp/slimport_custom_declare.h#L73 > >> > >> This address is 0x78 on my Nexus 5. Given [3] above it looks like we > >> need to support both addresses. What do you think about moving these > >> addresses into device tree? > > > > Assuming that the device supports different addresses (I can't validate > > that as I don't have access to the datasheet), and different addresses > > need to be used on different systems, then the address to be used needs > > to be provided by the firmware (DT in this case). Two options are > > possible, either specifying the address explicitly in the device's DT > > node, or specifying free addresses (in the form of a white list or black > > list) and allocating an address from that pool. The latter has been > > discussed in a BoF at the Linux Plumbers Conference last week, > > https://linuxplumbersconf.org/event/4/contributions/542/. > > > >> The downstream and upstream kernel sources divide these addresses by two > >> to get the i2c address. Here's the code in upstream: > >> > >> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix-anx78xx.c#L1353 > >> https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/bridge/analogix-anx78xx.c#L41 > >> > >> I'm not sure why the actual i2c address isn't used in this code. > > > > The ANX7802/12/14/16 has a slave I2C bus that provides the interface to access > or control the chip from the AP. The I2C slave addresses used to control the > ANX7802/12/14/16 are 70h, 72h, 7Ah, 7Eh and 80h. Every address allows you to > access to different registers of the chip and AFAICS is not configurable. > > I don't think these addresses should be configured via DT but for the driver itself. > > My wild guess is that the ANX7808 has different addresses, but I don't have the > datasheet of this version. I'm able to communicate with the 7808 on my Nexus 5 using the 0x78 address. Given that the addresses appear to be fixed per model, maybe it makes sense to drop the address #defines and add the addresses to the data pointer in the driver's of_match_table like so: static const struct of_device_id anx78xx_match_table[] = { { .compatible = "analogix,anx7808", .data = PTR_TO_7808_ADDRS }, { .compatible = "analogix,anx7812", .data = PTR_TO_781X_ADDRS }, { .compatible = "analogix,anx7814", .data = PTR_TO_781X_ADDRS }, { .compatible = "analogix,anx7818", .data = PTR_TO_781X_ADDRS }, { /* sentinel */ }, }; Brian
