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. Best regards, Enric
