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Subject: Re: [PATCH v7 6/7] serial: omap: do not override settings for RS485
 support
To: =?UTF-8?Q?Ilpo_J=c3=a4rvinen?= <ilpo.jarvinen@linux.intel.com>,
 Lino Sanfilippo <l.sanfilippo@kunbus.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Jiri Slaby <jirislaby@kernel.org>, u.kleine-koenig@pengutronix.de,
 shawnguo@kernel.org, s.hauer@pengutronix.de, mcoquelin.stm32@gmail.com,
 alexandre.torgue@foss.st.com, cniedermaier@dh-electronics.com,
 hugo@hugovil.com, m.brock@vanmierlo.com, LKML
 <linux-kernel@vger.kernel.org>, linux-serial <linux-serial@vger.kernel.org>,
 Lukas Wunner <lukas@wunner.de>, p.rosenberger@kunbus.com,
 stable@vger.kernel.org
References: <20240103061818.564-1-l.sanfilippo@kunbus.com>
 <20240103061818.564-7-l.sanfilippo@kunbus.com>
 <c88034d4-cb5-b64e-7a76-194ef35f28@linux.intel.com>
From: Lino Sanfilippo <LinoSanfilippo@gmx.de>
Message-ID: <a41ae447-565a-4db3-96ff-30aef6455a7c@gmx.de>
Date: Fri, 5 Jan 2024 13:42:41 +0100
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On 03.01.24 at 12:36, Ilpo J=E4rvinen wrote:
> On Wed, 3 Jan 2024, Lino Sanfilippo wrote:
>
>> The drivers RS485 support is deactivated if there is no RTS GPIO availa=
ble.
>> This is done by nullifying the ports rs485_supported struct. After that
>> however the settings in serial_omap_rs485_supported are assigned to the
>> same structure unconditionally, which results in an unintended reactiva=
tion
>> of RS485 support.
>>
>> Fix this by moving the assignment to the beginning of
>> serial_omap_probe_rs485() and thus before uart_get_rs485_mode() gets
>> called.
>
> This doesn't seem to accurately reflect what the problem is (which you
> correctly described in the paragraph above this). The problem doesn't se=
em
> to have anything to do with the placement of uart_get_rs485_mode() call
> but the if (IS_ERR(up->rts_gpiod)) block that clears rs485_supported?
>

Right, this should be "...Fix this by moving the assignment to the beginni=
ng of
serial_omap_probe_rs485() and thus before the check for the RTS GPIO."
I will correct this.


> A future work item that came to my mind while reviewing this: I suppose
> uart_disable_rs485_support() could be added into core which memsets
> rs485_supported and rs485 to zero so this driver could just call it.
>

Yes, and the ar933x driver could use that as well.


Regards,
Lino