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Date: Mon, 5 Oct 2020 10:22:40 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Jerome Brunet <jbrunet@...libre.com>,
Kevin Hilman <khilman@...libre.com>,
"open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
Brad Harper <bjharper@...il.com>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] mmc: meson-gx: remove IRQF_ONESHOT
+ Tglx
On Fri, 2 Oct 2020 at 18:49, Jerome Brunet <jbrunet@...libre.com> wrote:
>
> IRQF_ONESHOT was added to this driver to make sure the irq was not enabled
> again until the thread part of the irq had finished doing its job.
>
> Doing so upsets RT because, under RT, the hardirq part of the irq handler
> is not migrated to a thread if the irq is claimed with IRQF_ONESHOT.
> In this case, it has been reported to eventually trigger a deadlock with
> the led subsystem.
>
> Preventing RT from doing this migration was certainly not the intent, the
> description of IRQF_ONESHOT does not really reflect this constraint:
>
> > IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
> > Used by threaded interrupts which need to keep the
> > irq line disabled until the threaded handler has been run.
>
> This is exactly what this driver was trying to acheive so I'm still a bit
> confused whether this is a driver or an RT issue.
>
> Anyway, this can be solved driver side by manually disabling the IRQs
> instead of the relying on the IRQF_ONESHOT. IRQF_ONESHOT may then be removed
> while still making sure the irq won't trigger until the threaded part of
> the handler is done.
Thomas, may I have your opinion on this one.
I have no problem to apply $subject patch, but as Jerome also
highlights above - this kind of makes me wonder if this is an RT
issue, that perhaps deserves to be solved in a generic way.
What do you think?
Kind regards
Uffe
>
> Fixes: eb4d81127746 ("mmc: meson-gx: correct irq flag")
> Reported-by: Brad Harper <bjharper@...il.com>
> Cc: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
> ---
> drivers/mmc/host/meson-gx-mmc.c | 47 ++++++++++++++++++++-------------
> 1 file changed, 29 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/mmc/host/meson-gx-mmc.c b/drivers/mmc/host/meson-gx-mmc.c
> index 08a3b1c05acb..effc356db904 100644
> --- a/drivers/mmc/host/meson-gx-mmc.c
> +++ b/drivers/mmc/host/meson-gx-mmc.c
> @@ -101,8 +101,7 @@
> #define IRQ_RESP_STATUS BIT(14)
> #define IRQ_SDIO BIT(15)
> #define IRQ_EN_MASK \
> - (IRQ_CRC_ERR | IRQ_TIMEOUTS | IRQ_END_OF_CHAIN | IRQ_RESP_STATUS |\
> - IRQ_SDIO)
> + (IRQ_CRC_ERR | IRQ_TIMEOUTS | IRQ_END_OF_CHAIN)
>
> #define SD_EMMC_CMD_CFG 0x50
> #define SD_EMMC_CMD_ARG 0x54
> @@ -170,6 +169,7 @@ struct meson_host {
> dma_addr_t descs_dma_addr;
>
> int irq;
> + u32 irq_en;
>
> bool vqmmc_enabled;
> };
> @@ -842,22 +842,24 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
> struct meson_host *host = dev_id;
> struct mmc_command *cmd;
> struct mmc_data *data;
> - u32 irq_en, status, raw_status;
> + u32 status, raw_status;
> irqreturn_t ret = IRQ_NONE;
>
> - irq_en = readl(host->regs + SD_EMMC_IRQ_EN);
> + /* Disable irqs */
> + writel(0, host->regs + SD_EMMC_IRQ_EN);
> +
> raw_status = readl(host->regs + SD_EMMC_STATUS);
> - status = raw_status & irq_en;
> + status = raw_status & host->irq_en;
>
> if (!status) {
> dev_dbg(host->dev,
> "Unexpected IRQ! irq_en 0x%08x - status 0x%08x\n",
> - irq_en, raw_status);
> - return IRQ_NONE;
> + host->irq_en, raw_status);
> + goto none;
> }
>
> if (WARN_ON(!host) || WARN_ON(!host->cmd))
> - return IRQ_NONE;
> + goto none;
>
> /* ack all raised interrupts */
> writel(status, host->regs + SD_EMMC_STATUS);
> @@ -908,6 +910,11 @@ static irqreturn_t meson_mmc_irq(int irq, void *dev_id)
> if (ret == IRQ_HANDLED)
> meson_mmc_request_done(host->mmc, cmd->mrq);
>
> +none:
> + /* Enable the irq again if the thread will not run */
> + if (ret != IRQ_WAKE_THREAD)
> + writel(host->irq_en, host->regs + SD_EMMC_IRQ_EN);
> +
> return ret;
> }
>
> @@ -934,15 +941,17 @@ static irqreturn_t meson_mmc_irq_thread(int irq, void *dev_id)
> struct mmc_command *next_cmd, *cmd = host->cmd;
> struct mmc_data *data;
> unsigned int xfer_bytes;
> + int ret = IRQ_HANDLED;
>
> - if (WARN_ON(!cmd))
> - return IRQ_NONE;
> + if (WARN_ON(!cmd)) {
> + ret = IRQ_NONE;
> + goto out;
> + }
>
> if (cmd->error) {
> meson_mmc_wait_desc_stop(host);
> meson_mmc_request_done(host->mmc, cmd->mrq);
> -
> - return IRQ_HANDLED;
> + goto out;
> }
>
> data = cmd->data;
> @@ -959,7 +968,10 @@ static irqreturn_t meson_mmc_irq_thread(int irq, void *dev_id)
> else
> meson_mmc_request_done(host->mmc, cmd->mrq);
>
> - return IRQ_HANDLED;
> +out:
> + /* Re-enable the irqs */
> + writel(host->irq_en, host->regs + SD_EMMC_IRQ_EN);
> + return ret;
> }
>
> /*
> @@ -1133,13 +1145,12 @@ static int meson_mmc_probe(struct platform_device *pdev)
>
> /* clear, ack and enable interrupts */
> writel(0, host->regs + SD_EMMC_IRQ_EN);
> - writel(IRQ_CRC_ERR | IRQ_TIMEOUTS | IRQ_END_OF_CHAIN,
> - host->regs + SD_EMMC_STATUS);
> - writel(IRQ_CRC_ERR | IRQ_TIMEOUTS | IRQ_END_OF_CHAIN,
> - host->regs + SD_EMMC_IRQ_EN);
> + host->irq_en = IRQ_EN_MASK;
> + writel(host->irq_en, host->regs + SD_EMMC_STATUS);
> + writel(host->irq_en, host->regs + SD_EMMC_IRQ_EN);
>
> ret = request_threaded_irq(host->irq, meson_mmc_irq,
> - meson_mmc_irq_thread, IRQF_ONESHOT,
> + meson_mmc_irq_thread, 0,
> dev_name(&pdev->dev), host);
> if (ret)
> goto err_init_clk;
> --
> 2.25.4
>
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