RE: [PATCH] i2c: cadence: Fix regression with bus recovery

["Datta, Shubhrajyoti" <shubhrajyoti.datta@amd.com>]

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[AMD Official Use Only - General]


Hi ,
Thanks for the patch

> -----Original Message-----
> From: carsten.haitzler@foss.arm.com <carsten.haitzler@foss.arm.com>
> Sent: Friday, November 25, 2022 5:21 PM
> To: michal.simek@xilinx.com; shubhrajyoti.datta@xilinx.com; linux-arm-
> kernel@lists.infradead.org; linux-i2c@vger.kernel.org; linux-
> kernel@vger.kernel.org
> Cc: torvalds@linux-foundation.org
> Subject: [PATCH] i2c: cadence: Fix regression with bus recovery
> 
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> 
> 
> From: Carsten Haitzler <carsten.haitzler@arm.com>
> 
> Commit "i2c: cadence: Add standard bus recovery support" breaks for i2c
> devices that have no pinctrl defined. There is no requirement for this to exist
> in the DT. This has worked perfectly well without this before in at least 1 real
> usage case on hardware (Mali Komeda DPU, Cadence i2c to talk to a tda99xx
> phy). Adding the requirement to have pinctrl set up in the device tree (or
> otherwise be found) is a regression where the whole i2c device is lost
> entirely (in this case dropping entire devices which then leads to the drm
> display stack unable to find the phy for display output, thus having no drm
> display device and so on down the chain).
> 
> This converts the above commit to an enhancement if pinctrl can be found
> for the i2c device, providing a timeout on read with recovery, but if not, do
> what used to be done rather than a fatal loss of a device.
> 
> This restores the mentioned display devices to their working state again.
> 
> Fixes: 58b924241d0a ("i2c: cadence: Add standard bus recovery support")
> Signed-off-by: Carsten Haitzler <carsten.haitzler@arm.com>
> ---
> Note: This issue was discovered during the porting of the linux kernel on
> Morello [1].
> 
> [1]
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgit.
> morello-
> project.org%2Fmorello%2Fkernel%2Flinux&amp;data=05%7C01%7Cshubhraj
> yoti.datta%40amd.com%7C651e141296fb497b6c2e08dacedb65ad%7C3dd896
> 1fe4884e608e11a82d994e183d%7C0%7C0%7C638049738949855658%7CUnkn
> own%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik
> 1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=ny08zTdgJKxXC
> dwYaCWFS3mwd65LDqFAIYfjao6gO8Y%3D&amp;reserved=0
> ---
>  drivers/i2c/busses/i2c-cadence.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-cadence.c b/drivers/i2c/busses/i2c-
> cadence.c
> index fe0cd205502d..40d0cc6bb996 100644
> --- a/drivers/i2c/busses/i2c-cadence.c
> +++ b/drivers/i2c/busses/i2c-cadence.c
> @@ -852,7 +852,8 @@ static int cdns_i2c_master_xfer(struct i2c_adapter
> *adap, struct i2c_msg *msgs,
>                                          CDNS_I2C_POLL_US, CDNS_I2C_TIMEOUT_US);
>         if (ret) {
>                 ret = -EAGAIN;
> -               i2c_recover_bus(adap);
> +               if (id->adap.bus_recovery_info)
> +                       i2c_recover_bus(adap);
>                 goto out;
>         }
> 
> @@ -1262,10 +1263,10 @@ static int cdns_i2c_probe(struct platform_device
> *pdev)
>         }
> 
>         id->rinfo.pinctrl = devm_pinctrl_get(&pdev->dev);
> -       if (IS_ERR(id->rinfo.pinctrl)) {
> +       if (IS_ERR(id->rinfo.pinctrl))
>                 dev_info(&pdev->dev, "can't get pinctrl, bus recovery not
> supported\n");
> -               return PTR_ERR(id->rinfo.pinctrl);
> -       }
> +       else
> +               id->adap.bus_recovery_info = &id->rinfo;

May be we could differentiate between  ENODEV and  other errors.
As we want to do this for the case when it is not provided.


> 
>         id->membase = devm_platform_get_and_ioremap_resource(pdev, 0,
> &r_mem);
>         if (IS_ERR(id->membase))
> @@ -1283,7 +1284,6 @@ static int cdns_i2c_probe(struct platform_device
> *pdev)
>         id->adap.retries = 3;           /* Default retry value. */
>         id->adap.algo_data = id;
>         id->adap.dev.parent = &pdev->dev;
> -       id->adap.bus_recovery_info = &id->rinfo;
>         init_completion(&id->xfer_done);
>         snprintf(id->adap.name, sizeof(id->adap.name),
>                  "Cadence I2C at %08lx", (unsigned long)r_mem->start);
> --
> 2.32.0

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