linux-kernel - Re: [PATCH v2 2/2] firmware: add exynos acpm driver

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Message-ID: <2941d65e-8fb4-4d5a-be4b-283de2cb3274@linaro.org>
Date: Wed, 23 Oct 2024 10:53:24 +0100
From: Tudor Ambarus <tudor.ambarus@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>, jassisinghbrar@...il.com
Cc: alim.akhtar@...sung.com, mst@...hat.com, javierm@...hat.com,
 tzimmermann@...e.de, bartosz.golaszewski@...aro.org,
 luzmaximilian@...il.com, sudeep.holla@....com, conor.dooley@...rochip.com,
 bjorn@...osinc.com, ulf.hansson@...aro.org,
 linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, marcan@...can.st, neal@...pa.dev,
 alyssa@...enzweig.io, broonie@...nel.org, andre.draszik@...aro.org,
 willmcvicker@...gle.com, peter.griffin@...aro.org, kernel-team@...roid.com,
 vincent.guittot@...aro.org, daniel.lezcano@...aro.org
Subject: Re: [PATCH v2 2/2] firmware: add exynos acpm driver



On 10/23/24 10:00 AM, Krzysztof Kozlowski wrote:
>>>>> I also cannot find any piece of code setting several of above, e.g. tx_base
>>>> I'm not writing any SRAM configuration fields, these fields are used to
>>>> read/retrive the channel parameters from SRAM.
>>> I meany tx_base is always 0. Where is this property set? Ever?
>> It's not zero. My assumption is it is set in the acpm firmware, but I
> Where is any assignment to this member?

In probe() you'll see that exynos_acpm->shmem is a pointer in SRAM to a
struct exynos_acpm_shmem __iomem *shmem;

Then in:

static int exynos_acpm_chans_init()
{
	struct exynos_acpm_shmem_chan __iomem *shmem_chans, *shmem_chan;
	struct exynos_acpm_shmem __iomem *shmem = exynos_acpm->shmem;
	...

	shmem_chans = exynos_acpm_get_iomem_addr(exynos_acpm->sram_base,
						 &shmem->chans);
	...
}

shmem->chans is not initialized (or tx_base). I'm using its address in
SRAM (&shmem->chans) which I then read it with readl_relaxed().

I guess one can do the same using offsetof:
shmem_chans = readl_realaxed(shmem + offsetof(struct exynos_acpm_shmem,
					      chans));

Thanks,
ta