On 5/2/23 12:19, Krzysztof Kozlowski wrote:
On 02/05/2023 12:14, Guntupalli, Manikanta wrote:
Hi Rob Herring,
-----Original Message-----
From: Rob Herring <robh@xxxxxxxxxx>
Sent: Thursday, April 27, 2023 10:14 PM
To: Guntupalli, Manikanta <manikanta.guntupalli@xxxxxxx>
Cc: gregkh@xxxxxxxxxxxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx;
michal.simek@xxxxxxxxxx; linux-serial@xxxxxxxxxxxxxxx;
devicetree@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
jirislaby@xxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; Simek, Michal
<michal.simek@xxxxxxx>; git (AMD-Xilinx) <git@xxxxxxx>; Pandey,
Radhey Shyam <radhey.shyam.pandey@xxxxxxx>; Datta, Shubhrajyoti
<shubhrajyoti.datta@xxxxxxx>; Goud, Srinivas <srinivas.goud@xxxxxxx>;
manion05gk@xxxxxxxxx
Subject: Re: [PATCH 1/2] dt-bindings: Add optional gpio property to uartps
node to support rs485
On Wed, Apr 26, 2023 at 05:59:46PM +0530, Manikanta Guntupalli wrote:
Add optional gpio property to uartps node and add reference to rs485.yaml
The diff tells me that already. Why?
Please check Figure 11-3 (Page number 37) in the below mentioned data sheet, It shows PMOD (ISOW14x2) devices used in half duplex configuration. Driver outputs Y and Z are shorted to A and B respectively. This reduces overall cabling requirements. Also DE/RE are shorted to each other, and at a time, any node acts as either a driver or a receiver.
Using above optional GPIO controlling driver or a receiver. This GPIO is optional because it is not required for uart console node.
Here,
DE - Driver enable. If pin is floating, driver is disabled (internal pull-down resistor)
RE - Receiver enable. If pin is floating, receiver buffer is disabled (internal pull-up resistor)
Datasheet:
https://www.ti.com/lit/ds/symlink/isow1432.pdf?ts=1682607122706&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FISOW1432%252Fpart-details%252FISOW1432DFMR%253FkeyMatch%253DISOW1432DFMR%2526tisearch%253Dsearch-everything%2526usecase%253DOPN
Your request for us to get into some datasheet somewhere, to get the
answer to the basic question, is not reasonable. Commit must justify its
existence, not some external source.
Not really. Manual itself just shows picture of that connection if you are
interested.
On schematics it looks like that DE and /RE are just handle via one gpio. That's
why you need 3 wires instead of 4. Definitely it should be described better.
My concern was more about choosing proper name for this functionality.
Thanks,
Michal
