linux-kernel - Re: [PATCH 3/5] arm64: dts: exynos: gs101: use correct clocks for usi8

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Date: Mon, 29 Jan 2024 16:33:17 +0000
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Sam Protsenko <semen.protsenko@...aro.org>,
 André Draszik <andre.draszik@...aro.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: peter.griffin@...aro.org, robh+dt@...nel.org,
 krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 linux-kernel@...r.kernel.org, kernel-team@...roid.com,
 willmcvicker@...gle.com, alim.akhtar@...sung.com, s.nawrocki@...sung.com,
 tomasz.figa@...il.com, cw00.choi@...sung.com, mturquette@...libre.com,
 sboyd@...nel.org, linux-arm-kernel@...ts.infradead.org,
 linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH 3/5] arm64: dts: exynos: gs101: use correct clocks for
 usi8



On 1/27/24 04:00, Tudor Ambarus wrote:
>>> Wrong pclk clocks have been used in this usi8 instance here. For USI
>>> and I2C, we need the ipclk and pclk, where pclk is the bus clock.
>>> Without it, nothing can work.
>> Empty line is missing here?
>>
>>> It is unclear what exactly is using USI8_USI_CLK, but it is not
>>> required for the IP to be operational at this stage, while pclk is.
>> From [1] it looks like DIV_CLK_PERIC0_USI8_USI is a common parrent for
>> these two leaf gate clocks:
>>   1. GOUT_BLK_PERIC0_UID_RSTNSYNC_CLK_PERIC0_USI8_USI_IPCLKPORT_CLK
>>   2. GOUT_BLK_PERIC0_UID_PERIC0_TOP0_IPCLKPORT_IPCLK_7
>>
>> So IIUC, you replace clock #1 with clock #2 in this patch? If so, I
> No, GOUT_BLK_PERIC0_UID_PERIC0_TOP0_IPCLKPORT_IPCLK_7 is already used by
> IPCLK, the one that controls the clock frequency.
> 
> So I understand Andre' replaces a child of the USI8 with something else.
> 
> I don't think this works. We shall at least test it. I tested my usi8
> patches with the eeprom that's populated on the battery connector. I'll
> sync with Andre' offline and redo the tests on Monday.

Andre' is right, I messed up the bus clocks for USI. I tested the IPCLK,
the one that feeds USI clients, but I failed to correctly test the bus
clock. I retested by removing the clk_ignore_unused bootargs param and
verified that the patch is correct.

Reviewed-by: Tudor Ambarus <tudor.ambarus@...aro.org>
Tested-by: Tudor Ambarus <tudor.ambarus@...aro.org>