From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Peter Griffin <peter.griffin@linaro.org>
Cc: arnd@arndb.de, linux@roeck-us.net, wim@linux-watchdog.org,
alim.akhtar@samsung.com, jaewon02.kim@samsung.com,
semen.protsenko@linaro.org, kernel-team@android.com,
tudor.ambarus@linaro.org, andre.draszik@linaro.org,
saravanak@google.com, willmcvicker@google.com,
linux-fsd@tesla.com, linux-watchdog@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH v2 1/2] soc: samsung: exynos-pmu: Add regmap support for SoCs that protect PMU regs
Date: Mon, 5 Feb 2024 14:13:13 +0100 [thread overview]
Message-ID: <99828589-c0b5-456d-b250-6ad3e6085a91@linaro.org> (raw)
In-Reply-To: <CADrjBPoQmTRsFYRtxBxdvAoKK816O8XN3=hOJ3vBt8wbbbk-=Q@mail.gmail.com>
On 01/02/2024 13:51, Peter Griffin wrote:
> Hi Krzysztof,
>
> On Tue, 30 Jan 2024 at 16:01, Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 29/01/2024 22:19, Peter Griffin wrote:
>>> Some Exynos based SoCs like Tensor gs101 protect the PMU registers for
>>> security hardening reasons so that they are only accessible in el3 via an
>>> SMC call.
>>>
>>> As most Exynos drivers that need to write PMU registers currently obtain a
>>> regmap via syscon (phys, pinctrl, watchdog). Support for the above usecase
>>> is implemented in this driver using a custom regmap similar to syscon to
>>> handle the SMC call. Platforms that don't secure PMU registers, get a mmio
>>> regmap like before. As regmaps abstract out the underlying register access
>>> changes to the leaf drivers are minimal.
>>>
>>> A new API exynos_get_pmu_regmap_by_phandle() is provided for leaf drivers
>>> that currently use syscon_regmap_lookup_by_phandle(). This also handles
>>> deferred probing.
>>>
>>> Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
>>> ---
>>> drivers/soc/samsung/exynos-pmu.c | 227 ++++++++++++++++++++++++-
>>> include/linux/soc/samsung/exynos-pmu.h | 10 ++
>>> 2 files changed, 236 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/soc/samsung/exynos-pmu.c b/drivers/soc/samsung/exynos-pmu.c
>>> index 250537d7cfd6..7bcc144e53a2 100644
>>> --- a/drivers/soc/samsung/exynos-pmu.c
>>> +++ b/drivers/soc/samsung/exynos-pmu.c
>>> @@ -5,6 +5,7 @@
>>> //
>>> // Exynos - CPU PMU(Power Management Unit) support
>>>
>>> +#include <linux/arm-smccc.h>
>>> #include <linux/of.h>
>>> #include <linux/of_address.h>
>>> #include <linux/mfd/core.h>
>>> @@ -12,20 +13,159 @@
>>> #include <linux/of_platform.h>
>>> #include <linux/platform_device.h>
>>> #include <linux/delay.h>
>>> +#include <linux/regmap.h>
>>>
>>> #include <linux/soc/samsung/exynos-regs-pmu.h>
>>> #include <linux/soc/samsung/exynos-pmu.h>
>>>
>>> #include "exynos-pmu.h"
>>>
>>> +static struct platform_driver exynos_pmu_driver;
>>
>> I don't understand why do you need it. You can have only one
>> pmu_context. The moment you probe second one, previous becomes invalid.
>>
>> I guess you want to parse phandle and check if just in case if it points
>> to the right device, but still the original code is not ready for two
>> PMU devices. I say either this problem should be solved entirely,
>> allowing two devices, or just compare device node from phandle with
>> device node of exynos_pmu_context->dev and return -EINVAL on mismatches.
>
> Apologies I didn't answer your original question. This wasn't about
> having partial support for multiple pmu devices. It is being used by
> driver_find_device_by_of_node() in exynos_get_pmu_regmap_by_phandle()
> to determine that the exynos-pmu device has probed and therefore a
> pmu_context exists and a regmap has been created and can be returned
> to the caller (as opposed to doing a -EPROBE_DEFER).
>
> Is there some better/other API you recommend for this purpose? Just
> checking pmu_context directly seems racy, so I don't think we should
> do that.
Hm, I don't quite get why you cannot use of_find_device_by_node()?
Best regards,
Krzysztof
next prev parent reply other threads:[~2024-02-05 13:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-29 21:19 [PATCH v2 0/2] Add regmap support to exynos-pmu for protected PMU regs Peter Griffin
2024-01-29 21:19 ` [PATCH v2 1/2] soc: samsung: exynos-pmu: Add regmap support for SoCs that protect " Peter Griffin
2024-01-29 23:01 ` Sam Protsenko
2024-01-30 14:51 ` Peter Griffin
2024-01-30 6:26 ` Guenter Roeck
2024-01-30 15:01 ` Peter Griffin
2024-01-30 16:01 ` Krzysztof Kozlowski
2024-02-01 11:29 ` Peter Griffin
2024-02-05 11:03 ` Krzysztof Kozlowski
2024-02-01 12:51 ` Peter Griffin
2024-02-05 13:13 ` Krzysztof Kozlowski [this message]
2024-02-07 11:42 ` Peter Griffin
2024-02-07 14:48 ` Krzysztof Kozlowski
2024-01-29 21:19 ` [PATCH v2 2/2] watchdog: s3c2410_wdt: use exynos_get_pmu_regmap_by_phandle() for " Peter Griffin
2024-01-29 22:25 ` Saravana Kannan
2024-01-30 3:38 ` Sam Protsenko
2024-01-30 15:31 ` Peter Griffin
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