linux-kernel - Re: [PATCH v2 2/5] soc: samsung: Add USI driver

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Message-ID: <3d3c201c-fcfe-0ebc-5a09-52ba2220bc35@canonical.com>
Date:   Tue, 30 Nov 2021 09:25:00 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Jiri Slaby <jirislaby@...nel.org>,
        Jaewon Kim <jaewon02.kim@...sung.com>,
        Chanho Park <chanho61.park@...sung.com>,
        David Virag <virag.david003@...il.com>,
        Youngmin Nam <youngmin.nam@...sung.com>,
        devicetree@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v2 2/5] soc: samsung: Add USI driver

On 30/11/2021 03:31, Sam Protsenko wrote:
> On Tue, 30 Nov 2021 at 04:24, Sam Protsenko <semen.protsenko@...aro.org> wrote:
>>
>> USIv2 IP-core is found on modern ARM64 Exynos SoCs (like Exynos850) and
>> provides selectable serial protocol (one of: UART, SPI, I2C). USIv2
>> registers usually reside in the same register map as a particular
>> underlying protocol it implements, but have some particular offset. E.g.
>> on Exynos850 the USI_UART has 0x13820000 base address, where UART
>> registers have 0x00..0x40 offsets, and USI registers have 0xc0..0xdc
>> offsets. Desired protocol can be chosen via SW_CONF register from System
>> Register block of the same domain as USI.
>>
>> Before starting to use a particular protocol, USIv2 must be configured
>> properly:
>>   1. Select protocol to be used via System Register
>>   2. Clear "reset" flag in USI_CON
>>   3. Configure HWACG behavior (e.g. for UART Rx the HWACG must be
>>      disabled, so that the IP clock is not gated automatically); this is
>>      done using USI_OPTION register
>>   4. Keep both USI clocks (PCLK and IPCLK) running during USI registers
>>      modification
>>
>> This driver implements above behavior. Of course, USIv2 driver should be
>> probed before UART/I2C/SPI drivers. It can be achived by embedding
>> UART/I2C/SPI nodes inside of USI node (in Device Tree); driver then
>> walks underlying nodes and instantiates those. Driver also handles USI
>> configuration on PM resume, as register contents can be lost during CPU
>> suspend.
>>
>> This driver is designed with different USI versions in mind. So it
>> should be relatively easy to add new USI revisions to it later.
>>
>> Signed-off-by: Sam Protsenko <semen.protsenko@...aro.org>
>> ---
> 
> I'm sorry for sending this v2 series as a bunch of separate mails. My
> msmtp failed in the middle of submission, two times in a row. If it's
> a bother, please tell me and I'll re-send as v3.
> 

You can always fix it by using --in-reply-to and --no-thread. This
unfortunately breaks b4, so please resend (can be v2 RESEND):

Looking up
https://lore.kernel.org/r/20211130022250.28519-1-semen.protsenko%40linaro.org

Grabbing thread from
lore.kernel.org/all/20211130022250.28519-1-semen.protsenko%40linaro.org/t.mbox.gz

Analyzing 2 messages in the thread

Checking attestation on all messages, may take a moment...

  ✓ [PATCH v2 1/5] dt-bindings: soc: samsung: Add Exynos USI bindings

    ✓ Signed: DKIM/linaro.org

  ERROR: missing [2/5]!

  ERROR: missing [3/5]!

  ERROR: missing [4/5]!

  ERROR: missing [5/5]!




Best regards,
Krzysztof