From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Simek Date: Tue, 5 May 2020 10:26:38 +0200 Subject: Calling i2c set speed twice for i2c_mux_bus In-Reply-To: References: Message-ID: <81ef897f-4a16-5d6b-d183-f7bf03ec7aa1@xilinx.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 15. 04. 20 8:40, Michal Simek wrote: > On 10. 04. 20 10:49, Heiko Schocher wrote: >> Hello Michal, >> >> Am 10.04.2020 um 08:46 schrieb Michal Simek: >>> Hi Heiko, >>> >>> On 10. 04. 20 7:11, Heiko Schocher wrote: >>>> Hello Michal, >>>> >>>> Am 09.04.2020 um 16:03 schrieb Michal Simek: >>>>> Hi Heiko and Simon, >>>>> >>>>> I have find out one bug in i2c class. I am using zcu104 revC board >>>>> which >>>>> has dts in mainline where i2c1 has i2c mux with some channels. >>>>> In DT clock-frequency = <400000>; is specified and it is read in >>>>> i2c_post_probe(). But i2c_mux_bus_drv is also UCLASS_I2C which means >>>>> that post probe is called for it too. And because clock-frequency >>>>> property is not there default 100k is used. >>>>> >>>>> I think that is bug and should be fixed. >>>>> Heiko: Are you aware about this issue? >>>> >>>> No :-( >>>> >>>> The question is, is this a bug? >>> >>> I have never seen clock-frequency property in i2c mux bus node. Also I >>> have looked at linux dt binding docs and nothing like that is specified >>> there. From quick look also pca954x driver is not reading it. >> >> Indeed. >> >>>> Should a i2c bus behind a mux not be able to set his own speed? >>> >>> Not sure if that make sense but Linux will likely ignore it. I am not >>> saying it doesn't make sense but I haven't seen this feature. >> >> Ok. >> >>>> But may as a feature (or bugfix?) if "clock-frequency" is not there, >>>> use the speed of the parent bus...? >>> >>> I was thinking about this too. >>> just c&p quick implementation would look like this. Because it is >>> i2c->i2c_mux->i2c. But maybe there is a better way how to do it. >>> >>> diff --git a/drivers/i2c/i2c-uclass.c b/drivers/i2c/i2c-uclass.c >>> index 2aa3efe8aaa0..982c467deba3 100644 >>> --- a/drivers/i2c/i2c-uclass.c >>> +++ b/drivers/i2c/i2c-uclass.c >>> @@ -640,9 +640,21 @@ static int i2c_post_probe(struct udevice *dev) >>> ? { >>> ? #if CONFIG_IS_ENABLED(OF_CONTROL) && !CONFIG_IS_ENABLED(OF_PLATDATA) >>> ???????? struct dm_i2c_bus *i2c = dev_get_uclass_priv(dev); >>> +?????? int parent_speed = I2C_SPEED_STANDARD_RATE; >>> + >>> +?????? if (dev->parent && >>> +?????????? device_get_uclass_id(dev->parent) == UCLASS_I2C_MUX && >>> +?????????? dev->parent->parent && >>> +?????????? device_get_uclass_id(dev->parent->parent) == UCLASS_I2C) { >>> +?????????????? struct dm_i2c_bus *i2c_parent; >>> + >>> +?????????????? i2c_parent = dev_get_uclass_priv(dev->parent->parent); >>> +?????????????? parent_speed = i2c_parent->speed_hz; >>> +?????????????? /* Not sure if make sense to check that parent_speed is >>> not 0 */ >> >> I think this check is not needed. >> >>> +?????? } >>> >>> ???????? i2c->speed_hz = dev_read_u32_default(dev, "clock-frequency", >>> -??????????????????????????????????????????? I2C_SPEED_STANDARD_RATE); >>> +??????????????????????????????????????????? parent_speed); >> >> Wow, a big if ... may this is clearer (not compile tested)? >> >> udevice *parent = dev_get_parent(dev); >> >> if (parent && device_get_uclass_id(parent) == UCLASS_I2C_MUX) { >> ????udevice *parent2 = dev_get_parent(parent); >> ????if (parent2 && device_get_uclass_id(parent2) == UCLASS_I2C) { >> ??????? struct dm_i2c_bus *i2cp = dev_get_uclass_priv(parent2); >> >> ??????? parent_speed = i2cp->speed_hz; >> ????} >> } >> >> but Simon has a deeper DM knowledge, may there is a better approach. > > Simon: any comment on this one? Simon: Can you please comment this? Thanks, Michal