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Wed, 22 Oct 2025 04:35:02 -0700 (PDT) Message-ID: <804dd1f5-7e79-4bfa-b777-c97bb89a713a@gmail.com> Date: Wed, 22 Oct 2025 04:35:00 -0700 Precedence: bulk X-Mailing-List: linux-clk@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 5/8] reset: imx8mp-audiomix: Switch to using regmap API To: Frank Li Cc: Abel Vesa , Peng Fan , Michael Turquette , Stephen Boyd , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Shawn Guo , Fabio Estevam , Philipp Zabel , Daniel Baluta , Shengjiu Wang , linux-clk@vger.kernel.org, imx@lists.linux.dev, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Pengutronix Kernel Team References: <20251017112025.11997-1-laurentiumihalcea111@gmail.com> <20251017112025.11997-6-laurentiumihalcea111@gmail.com> Content-Language: en-US From: Laurentiu Mihalcea In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 10/17/2025 7:49 AM, Frank Li wrote: > On Fri, Oct 17, 2025 at 04:20:22AM -0700, Laurentiu Mihalcea wrote: >> From: Laurentiu Mihalcea >> >> As far as the Linux kernel is concerned, block devices such as i.MX8MP's >> AUDIOMIX block control or i.MX8ULP's SIM LPAV can simultaneously act as >> clock controllers, reset controllers or mux controllers. Since these IPs >> offer different functionalities through different subsystem APIs, it's >> important to make sure that the register R-M-W cycles are performed under >> the same lock across all subsystem APIs. This will ensure that registers >> will not end up with the wrong values because of race conditions (e.g. >> clock consumer tries to update block control register A, while, at the >> same time, reset consumer tries to update the same block control register). >> >> However, the aforementioned race conditions will only impact block control >> IPs which use the same register for multiple functionalities. For example, >> i.MX8MP's AUDIOMIX block control IP provides clock gating functionalities >> and reset control functionalities through different registers. This is why >> the current approach (i.e. clock control and reset control work using >> different locks) has worked well so far. >> >> Since we want to extend this driver to be usable for i.MX8ULP's SIM LPAV >> block control IP, we need to make sure that clock control, reset control, >> and mux control APIs use the same lock since all of these functionalities >> are performed using the SYSCTRL0 register. >> >> To do so, we need to switch to the regmap API and, if possible, use the >> parent device's regmap, which, in the case of i.MX8ULP, will be the clock >> controller. This way, we can make sure that the clock gates and the reset >> controller will use the same lock to perform the register R-M-W cycles. >> >> This change will also work fine for cases where we don't really need to >> share the lock across multiple APIs (e.g. i.MX8MP's AUDIOMIX block >> control) since regmap will take care of the locking we were previously >> explicitly performing in the driver. >> >> The transition to the regmap API also involves some cleanup. Specifically, >> we can make use of devres to unmap the device's memory and get rid of the >> memory mapping-related error paths and the remove() function altogether. >> >> Signed-off-by: Laurentiu Mihalcea >> --- >> drivers/reset/reset-imx8mp-audiomix.c | 95 +++++++++++++++++---------- >> 1 file changed, 61 insertions(+), 34 deletions(-) >> >> diff --git a/drivers/reset/reset-imx8mp-audiomix.c b/drivers/reset/reset-imx8mp-audiomix.c >> index e9643365a62c..c74ce6e04177 100644 >> --- a/drivers/reset/reset-imx8mp-audiomix.c >> +++ b/drivers/reset/reset-imx8mp-audiomix.c >> @@ -11,6 +11,7 @@ >> #include >> #include >> #include >> +#include >> #include >> >> #define IMX8MP_AUDIOMIX_EARC_RESET_OFFSET 0x200 >> @@ -19,6 +20,7 @@ >> struct imx8mp_reset_map { >> unsigned int offset; >> unsigned int mask; >> + unsigned int shift; >> bool active_low; >> }; >> >> @@ -26,24 +28,27 @@ static const struct imx8mp_reset_map reset_map[] = { >> [IMX8MP_AUDIOMIX_EARC_RESET] = { >> .offset = IMX8MP_AUDIOMIX_EARC_RESET_OFFSET, >> .mask = BIT(0), >> + .shift = 0, >> .active_low = true, >> }, >> [IMX8MP_AUDIOMIX_EARC_PHY_RESET] = { >> .offset = IMX8MP_AUDIOMIX_EARC_RESET_OFFSET, >> .mask = BIT(1), >> + .shift = 1, >> .active_low = true, >> }, >> [IMX8MP_AUDIOMIX_DSP_RUNSTALL] = { >> .offset = IMX8MP_AUDIOMIX_DSP_RUNSTALL_OFFSET, >> .mask = BIT(5), >> + .shift = 5, > why need shift? you can use ffs(mask) to get shift. > >> .active_low = false, >> }, >> }; >> >> struct imx8mp_audiomix_reset { >> struct reset_controller_dev rcdev; >> - spinlock_t lock; /* protect register read-modify-write cycle */ >> void __iomem *base; >> + struct regmap *regmap; >> }; >> >> static struct imx8mp_audiomix_reset *to_imx8mp_audiomix_reset(struct reset_controller_dev *rcdev) >> @@ -55,26 +60,15 @@ static int imx8mp_audiomix_update(struct reset_controller_dev *rcdev, >> unsigned long id, bool assert) >> { >> struct imx8mp_audiomix_reset *priv = to_imx8mp_audiomix_reset(rcdev); >> - void __iomem *reg_addr = priv->base; >> - unsigned int mask, offset, active_low; >> - unsigned long reg, flags; >> + unsigned int mask, offset, active_low, shift, val; >> >> mask = reset_map[id].mask; >> offset = reset_map[id].offset; >> active_low = reset_map[id].active_low; >> + shift = reset_map[id].shift; >> + val = (active_low ^ assert) << shift; >> >> - spin_lock_irqsave(&priv->lock, flags); >> - >> - reg = readl(reg_addr + offset); >> - if (active_low ^ assert) >> - reg |= mask; >> - else >> - reg &= ~mask; >> - writel(reg, reg_addr + offset); >> - >> - spin_unlock_irqrestore(&priv->lock, flags); >> - >> - return 0; >> + return regmap_update_bits(priv->regmap, offset, mask, val); >> } >> >> static int imx8mp_audiomix_reset_assert(struct reset_controller_dev *rcdev, >> @@ -94,6 +88,50 @@ static const struct reset_control_ops imx8mp_audiomix_reset_ops = { >> .deassert = imx8mp_audiomix_reset_deassert, >> }; >> >> +static const struct regmap_config regmap_config = { >> + .reg_bits = 32, >> + .val_bits = 32, >> + .reg_stride = 4, >> +}; >> + >> +/* assumption: registered only if not using parent regmap */ >> +static void imx8mp_audiomix_reset_iounmap(void *data) >> +{ >> + struct imx8mp_audiomix_reset *priv = dev_get_drvdata(data); >> + >> + iounmap(priv->base); >> +} >> + >> +/* assumption: dev_set_drvdata() is called before this */ >> +static int imx8mp_audiomix_reset_get_regmap(struct device *dev) >> +{ >> + struct imx8mp_audiomix_reset *priv; >> + int ret; >> + >> + priv = dev_get_drvdata(dev); >> + >> + /* try to use the parent's regmap */ >> + priv->regmap = dev_get_regmap(dev->parent, NULL); >> + if (priv->regmap) >> + return 0; >> + >> + /* ... if that's not possible then initialize the regmap right now */ >> + priv->base = of_iomap(dev->parent->of_node, 0); >> + if (!priv->base) >> + return dev_err_probe(dev, -ENOMEM, "failed to iomap address space\n"); >> + >> + ret = devm_add_action_or_reset(dev, imx8mp_audiomix_reset_iounmap, dev); >> + if (ret) >> + return dev_err_probe(dev, ret, "failed to register action\n"); >> + >> + priv->regmap = devm_regmap_init_mmio(dev, priv->base, ®map_config); >> + if (IS_ERR(priv->regmap)) >> + return dev_err_probe(dev, PTR_ERR(priv->regmap), >> + "failed to initialize regmap\n"); >> + >> + return 0; >> +} >> + >> static int imx8mp_audiomix_reset_probe(struct auxiliary_device *adev, >> const struct auxiliary_device_id *id) >> { >> @@ -105,36 +143,26 @@ static int imx8mp_audiomix_reset_probe(struct auxiliary_device *adev, >> if (!priv) >> return -ENOMEM; >> >> - spin_lock_init(&priv->lock); >> - >> priv->rcdev.owner = THIS_MODULE; >> priv->rcdev.nr_resets = ARRAY_SIZE(reset_map); >> priv->rcdev.ops = &imx8mp_audiomix_reset_ops; >> priv->rcdev.of_node = dev->parent->of_node; >> priv->rcdev.dev = dev; >> priv->rcdev.of_reset_n_cells = 1; >> - priv->base = of_iomap(dev->parent->of_node, 0); >> - if (!priv->base) >> - return -ENOMEM; >> >> + /* keep before call to imx8mp_audiomix_reset_init_regmap() */ >> dev_set_drvdata(dev, priv); >> >> + ret = imx8mp_audiomix_reset_get_regmap(dev); >> + if (ret) >> + return dev_err_probe(dev, ret, "failed to get regmap\n"); >> + >> ret = devm_reset_controller_register(dev, &priv->rcdev); >> if (ret) >> - goto out_unmap; >> + return dev_err_probe(dev, ret, >> + "failed to register reset controller\n"); >> >> return 0; >> - >> -out_unmap: >> - iounmap(priv->base); >> - return ret; >> -} >> - >> -static void imx8mp_audiomix_reset_remove(struct auxiliary_device *adev) >> -{ >> - struct imx8mp_audiomix_reset *priv = dev_get_drvdata(&adev->dev); >> - >> - iounmap(priv->base); >> } >> >> static const struct auxiliary_device_id imx8mp_audiomix_reset_ids[] = { >> @@ -147,7 +175,6 @@ MODULE_DEVICE_TABLE(auxiliary, imx8mp_audiomix_reset_ids); >> >> static struct auxiliary_driver imx8mp_audiomix_reset_driver = { >> .probe = imx8mp_audiomix_reset_probe, >> - .remove = imx8mp_audiomix_reset_remove, > cleanup imx8mp_audiomix_reset_remove need seperate patch. as things stand now, this bit belongs in the same patch as the switch to the regmap API because of the introduction of imx8mp_audiomix_reset_get_regmap(), which uses devres. This makes the remove() function incorrect and, thus, needs to be dropped. since the cleanup is quite trivial, I don't think this would justify purposely making imx8mp_audiomix_reset_get_regmap() not use devres in this patch and then transitioning to it in a subsequent patch. > > Frank > >> .id_table = imx8mp_audiomix_reset_ids, >> }; >> >> -- >> 2.43.0 >>