From: Marek Vasut <marex@denx.de>
To: Raviteja Narayanam <rna@xilinx.com>,
"linux-i2c@vger.kernel.org" <linux-i2c@vger.kernel.org>
Cc: Michal Simek <michals@xilinx.com>,
Shubhrajyoti Datta <shubhraj@xilinx.com>,
Wolfram Sang <wsa@kernel.org>, Srinivas Goud <sgoud@xilinx.com>
Subject: Re: [PATCH 2/5] i2c: xiic: Drop broken interrupt handler
Date: Tue, 25 Aug 2020 22:50:53 +0200 [thread overview]
Message-ID: <f34e3539-4f2a-669f-6bb1-0b95ebf6c51f@denx.de> (raw)
In-Reply-To: <SN4PR0201MB3486689C38889DB9360D524ECA570@SN4PR0201MB3486.namprd02.prod.outlook.com>
On 8/25/20 11:44 AM, Raviteja Narayanam wrote:
Hi,
[...]
>>>>>>> So, this local_irq_save()/local_irq_restore() is not related to
>>>>>>> exclusive access in the driver (xiic_process vs xiic_start), but
>>>>>>> to supply the
>>>>>> byte count to controller before it completes transmitting START and
>>>>>> slave address.
>>>>>>
>>>>>> But then shouldn't the XIIC IP be fixed / extended with support for
>>>>>> such an atomic update instead ?
>>>>>
>>>>> I have started communicating with the hardware team on why the IP
>>>> behavior is like this.
>>>>
>>>> Any news from the hardware team ?
>>>
>>> " The expectation from the IP is un interrupted read i.e the read command
>> should be un interrupted and max delay expected is not more than 35-40 us
>> provided IIC frequency is 100 Khz. Please check if we can manage this in
>> Software. If delay is not managed enable iic control only after stop related
>> data is received"
>>> That was the response as is.
>>> The workaround suggested above is to enable the AXI I2C only after
>> second register write(STOP bit info with read count) is completed. This is not
>> generic, so we couldn't move forward.
>>> Our typical application scenario is like this "START WRITE, REPEATED START
>> READ, STOP". So, we must enable AXI I2C before read count is sent.
>>
>> So, if I understand it correctly, the XIIC IP is broken and cannot be fixed in
>> software reliably ? How shall we proceed then ?
>
> We are thinking of two options.
> 1. Trying for a SW fix to workaround this problem. Waiting on the HW IP team for any other suggestions.
> 2. XIIC IP has two modes of operation as stated in the user guide - Dynamic and Standard modes.
> Currently, the linux driver is using only dynamic mode and this bug appears here.
> The SW programming for standard mode is different and we are testing it for all possible use cases. Once
> That comes out successful, we will send out the patches.
Is this dynamic/standard mode switching what is already in the
downstream xilinx kernel tree ?
I think we should fix what is already upstream first, and only then add
more complexity.
[...]
next prev parent reply other threads:[~2020-08-25 20:53 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-13 15:07 [PATCH 1/5] i2c: xiic: Fix broken locking on tx_msg Marek Vasut
2020-06-13 15:07 ` [PATCH 2/5] i2c: xiic: Drop broken interrupt handler Marek Vasut
2020-06-17 12:25 ` Shubhrajyoti Datta
2020-06-17 12:31 ` Marek Vasut
2020-06-26 12:13 ` Raviteja Narayanam
2020-06-28 23:41 ` Marek Vasut
2020-06-29 12:52 ` Raviteja Narayanam
2020-06-29 21:50 ` Marek Vasut
2020-07-08 15:23 ` Raviteja Narayanam
2020-08-19 17:42 ` Marek Vasut
2020-08-24 8:27 ` Raviteja Narayanam
2020-08-24 11:58 ` Marek Vasut
2020-08-25 9:44 ` Raviteja Narayanam
2020-08-25 20:50 ` Marek Vasut [this message]
2020-09-07 8:51 ` Raviteja Narayanam
2020-09-08 14:04 ` Marek Vasut
2020-09-11 10:28 ` Michal Simek
2020-06-13 15:07 ` [PATCH 3/5] i2c: xiic: Defer xiic_wakeup() and __xiic_start_xfer() in xiic_process() Marek Vasut
2020-06-26 12:13 ` Raviteja Narayanam
2020-07-08 15:23 ` Raviteja Narayanam
2020-06-13 15:07 ` [PATCH 4/5] i2c: xiic: Switch from waitqueue to completion Marek Vasut
2020-06-26 12:13 ` Raviteja Narayanam
2020-06-28 23:41 ` Marek Vasut
2020-06-29 12:53 ` Raviteja Narayanam
2020-06-29 21:52 ` Marek Vasut
2020-06-13 15:07 ` [PATCH 5/5] i2c: xiic: Only ever transfer single message Marek Vasut
2020-06-13 19:33 ` Wolfram Sang
2020-06-13 19:37 ` Marek Vasut
2020-06-13 19:42 ` Wolfram Sang
2020-07-13 8:37 ` Michal Simek
2020-06-26 12:14 ` Raviteja Narayanam
2020-06-26 12:11 ` [PATCH 1/5] i2c: xiic: Fix broken locking on tx_msg Raviteja Narayanam
2020-06-28 23:18 ` Marek Vasut
2020-06-29 12:52 ` Raviteja Narayanam
2020-07-08 15:23 ` Raviteja Narayanam
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