Hi Krzysztof, Thanks for your review feedback. On Mon, 5 Feb 2024 at 13:13, Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx> wrote: > > On 01/02/2024 13:51, Peter Griffin wrote: > > Hi Krzysztof, > > > > On Tue, 30 Jan 2024 at 16:01, Krzysztof Kozlowski > > <krzysztof.kozlowski@xxxxxxxxxx> 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@xxxxxxxxxx> > >>> --- > >>> 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()? of_find_device_by_node() returns a platform_device, even if the driver hasn't probed. Whereas driver_find_device_by_of_node() iterates devices bound to a driver. If using of_find_device_by_node() API I could check the result of platform_get_drvdata(), and -EPROBE_DEFER if NULL (that pattern seems to be used by a few drivers). But that AFAIK only guarantees you reached the platform_set_drvdata() call in your driver probe() function, not that it has completed. IMHO the drivers using driver_find_device_by_of_node() for probe deferral are doing it more robustly than those using of_find_device_by_node() and checking if platform_get_drvdata() is NULL. Or is there some other way you had in mind of using of_find_device_by_node() I've not thought of to implement this? Thanks, Peter.
