linux-kernel - Re: [PATCH v1 2/3] dt-bindings: serial: samsung: add Exynos990 compatible

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Message-ID: <55028ae3-ffab-41e8-b1ec-fb2098b65d7c@linaro.org>
Date: Fri, 14 Feb 2025 06:42:14 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Denzeel Oliva <wachiturroxd150@...il.com>
Cc: alim.akhtar@...sung.com, conor+dt@...nel.org, devicetree@...r.kernel.org,
 gregkh@...uxfoundation.org, jirislaby@...nel.org, krzk+dt@...nel.org,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-samsung-soc@...r.kernel.org, linux-serial@...r.kernel.org,
 robh@...nel.org, semen.protsenko@...aro.org
Subject: Re: [PATCH v1 2/3] dt-bindings: serial: samsung: add Exynos990
 compatible



On 2/14/25 5:16 AM, Denzeel Oliva wrote:
> On Thu, Feb 13, 2025 at 07:20:22AM +0000, Tudor Ambarus wrote:
>> doesn't the 32 bit register restriction apply to uart as it applies to
>> SPI? If so, you shall probably fallback to gs101.
> 
> Of course not, downstream of the UART serial driver there is nothing
> specified about 32-bit access restriction, nothing explicitly
> in the driver. [0]
> 
> https://github.com/pascua28/android_kernel_samsung_s20fe/blob/3be539e9cd22b89ba3cc8282945a0c46ff27341d/drivers/tty/serial/samsung.c#L1543

that's very strange. uart and spi are part of the same USI IP, on the
same bus. I don't think you can have the same IP requiring 32 bit
accesses for SPI but allow 8-bit accesses for uart.

Maybe SPI can work with 8bit accesses? How did you test SPI and uart?