linux-kernel - Re: [PATCH v1 1/1] phy: ti: tusb1210: Don't check for write errors when powering on

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Message-ID: <bd21d5c6-ed5f-dd8c-f0bf-73f54ca8ee58@redhat.com>
Date:   Tue, 14 Jun 2022 13:23:21 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vinod Koul <vkoul@...nel.org>,
        Stephan Gerhold <stephan@...hold.net>,
        linux-phy@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Ferry Toth <ftoth@...londelft.nl>
Subject: Re: [PATCH v1 1/1] phy: ti: tusb1210: Don't check for write errors
 when powering on

Hi,

On 6/13/22 18:08, Andy Shevchenko wrote:
> On some platforms, like Intel Merrifield, the writing values during power on
> may timeout:
> 
>    tusb1210 dwc3.0.auto.ulpi: error -110 writing val 0x41 to reg 0x80
>    phy phy-dwc3.0.auto.ulpi.0: phy poweron failed --> -110
>    dwc3 dwc3.0.auto: error -ETIMEDOUT: failed to initialize core
>    dwc3: probe of dwc3.0.auto failed with error -110
> 
> which effectively fails the probe of the USB controller.
> Drop the check as it was before the culprit commit (see Fixes tag).
> 
> Fixes: 09a3512681b3 ("phy: ti: tusb1210: Improve ulpi_read()/_write() error checking")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Copy and pasting my reply about this in another thread to keep everyone up2date:

"""
In my experience with using the phy for charger-type detection on some
x86 android tablets which don't have any other way to do charger detection,
these errors indicate a real communication issue for reading/writing
phy registers. At the same time this usually does not seem to be a big
problem since the phy seems to work fine with its power-on defaults.

In case of Bay Trail these errors were related to 2 things:

1. Autosuspend of the phy-interface block in the dwc3, fixed by:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d7c93a903f33ff35aa0e6b5a8032eb9755b00826

But dwc3_pci_mrfld_properties[] already sets "snps,dis_u2_susphy_quirk",
so I guess it is not this.

2. There being no delay in tusb1210_power_on() between toggling the
reset IO and then trying to communicate with the phy, fixed in:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df37c99815d9e0775e67276d70c93cbc25f31c70

Maybe the:

#define TUSB1210_RESET_TIME_MS				30

Added by that commit needs to be a bit bigger for the possibly
older phy revision used on the merifield boards?

(note it is fine to just increase it a bit everywhere).
"""

IMHO it would be good to try and increase TUSB1210_RESET_TIME_MS (start with say 100
and then see if e.g. 50 also works). If increasing that does not work

I'm fine with going with this workaround patch to fix things.

Regards,

Hans

> ---
>  drivers/phy/ti/phy-tusb1210.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/phy/ti/phy-tusb1210.c b/drivers/phy/ti/phy-tusb1210.c
> index c3ab4b69ea68..669c13d6e402 100644
> --- a/drivers/phy/ti/phy-tusb1210.c
> +++ b/drivers/phy/ti/phy-tusb1210.c
> @@ -105,8 +105,9 @@ static int tusb1210_power_on(struct phy *phy)
>  	msleep(TUSB1210_RESET_TIME_MS);
>  
>  	/* Restore the optional eye diagram optimization value */
> -	return tusb1210_ulpi_write(tusb, TUSB1210_VENDOR_SPECIFIC2,
> -				   tusb->vendor_specific2);
> +	tusb1210_ulpi_write(tusb, TUSB1210_VENDOR_SPECIFIC2, tusb->vendor_specific2);
> +
> +	return 0;
>  }
>  
>  static int tusb1210_power_off(struct phy *phy)