From: Maxime Ripard <maxime@cerno.tech> To: Michael Wu <michael@allwinnertech.com> Cc: ulf.hansson@linaro.org, wens@csie.org, samuel@sholland.org, andre.przywara@arm.com, jernej.skrabec@gmail.com, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mmc: sunxi-mmc: check ocr_avail on resource request Date: Wed, 12 Jan 2022 10:34:15 +0100 [thread overview] Message-ID: <20220112093415.wdy3ht5yizw5lffl@houat> (raw) In-Reply-To: <20220104060325.3957-1-michael@allwinnertech.com> [-- Attachment #1: Type: text/plain, Size: 1731 bytes --] Hi, On Tue, Jan 04, 2022 at 02:03:25PM +0800, Michael Wu wrote: > Some platforms have no regulator, discrete power devices are used instead. Is it really the case? vmmc at least should be mandatory so a platform not having a regulator would violate the binding itself. > However, sunxi_mmc_probe does not catch this exception when regulator is > absent in DTS. This leads to sd or eMMC init failure. This will still happen with your patch though? > To solve this, a fixed vmmc regulator must be hooked up in DTS, like this: > reg_dummy_vmmc: dummy_vmmc { > compatible = "regulator-fixed"; > regulator-name = "dummy-vmmc"; > regulator-min-microvolt = <3300000>; > regulator-max-microvolt = <3300000>; > }; > > mmc0:mmc@4020000 { > compatible = "allwinner,sun50i-a100-emmc"; > device_type = "mmc0"; > vmmc-supply = <®_dummy_vmmc>; > } > > In this patch, we print an error message and abort the probe process if > the regulator is not specified in DTS. I'm fine with the patch itself, but it's really not clear to me what situation is being fixed or improved here. You're first mentioning that this is fixing the driver probing even if a regulator is absent, but then states (rightfully) that in such a case we should use a fixed regulator. So we should always have a regulator then? I assume that you want the driver to properly error out instead of going on if either a regulator is missing or if its voltages are out of range? If the former, then we should probably check if host->mmc->supply.vmmc returned an error. If the latter, then yes, checking ocr_avail is probably fine but we should make it clearer in the error message that it's what it's about. Maxime [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 228 bytes --]
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From: Maxime Ripard <maxime@cerno.tech> To: Michael Wu <michael@allwinnertech.com> Cc: ulf.hansson@linaro.org, wens@csie.org, samuel@sholland.org, andre.przywara@arm.com, jernej.skrabec@gmail.com, linux-mmc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mmc: sunxi-mmc: check ocr_avail on resource request Date: Wed, 12 Jan 2022 10:34:15 +0100 [thread overview] Message-ID: <20220112093415.wdy3ht5yizw5lffl@houat> (raw) In-Reply-To: <20220104060325.3957-1-michael@allwinnertech.com> [-- Attachment #1.1: Type: text/plain, Size: 1731 bytes --] Hi, On Tue, Jan 04, 2022 at 02:03:25PM +0800, Michael Wu wrote: > Some platforms have no regulator, discrete power devices are used instead. Is it really the case? vmmc at least should be mandatory so a platform not having a regulator would violate the binding itself. > However, sunxi_mmc_probe does not catch this exception when regulator is > absent in DTS. This leads to sd or eMMC init failure. This will still happen with your patch though? > To solve this, a fixed vmmc regulator must be hooked up in DTS, like this: > reg_dummy_vmmc: dummy_vmmc { > compatible = "regulator-fixed"; > regulator-name = "dummy-vmmc"; > regulator-min-microvolt = <3300000>; > regulator-max-microvolt = <3300000>; > }; > > mmc0:mmc@4020000 { > compatible = "allwinner,sun50i-a100-emmc"; > device_type = "mmc0"; > vmmc-supply = <®_dummy_vmmc>; > } > > In this patch, we print an error message and abort the probe process if > the regulator is not specified in DTS. I'm fine with the patch itself, but it's really not clear to me what situation is being fixed or improved here. You're first mentioning that this is fixing the driver probing even if a regulator is absent, but then states (rightfully) that in such a case we should use a fixed regulator. So we should always have a regulator then? I assume that you want the driver to properly error out instead of going on if either a regulator is missing or if its voltages are out of range? If the former, then we should probably check if host->mmc->supply.vmmc returned an error. If the latter, then yes, checking ocr_avail is probably fine but we should make it clearer in the error message that it's what it's about. Maxime [-- Attachment #1.2: signature.asc --] [-- Type: application/pgp-signature, Size: 228 bytes --] [-- Attachment #2: Type: text/plain, Size: 176 bytes --] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-01-12 9:34 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-01-04 6:03 [PATCH v2] mmc: sunxi-mmc: check ocr_avail on resource request Michael Wu 2022-01-04 6:03 ` Michael Wu 2022-01-12 9:34 ` Maxime Ripard [this message] 2022-01-12 9:34 ` Maxime Ripard 2022-01-12 10:37 ` Ulf Hansson 2022-01-12 10:37 ` Ulf Hansson
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