On Sun, 15 May 2011, Paul Parsons wrote:
> There is a race condition in the tmio_mmc_irq() interrupt handler,
> caused by the presence of a while loop, which results in warnings of
> spurious interrupts. This was found on an HP iPAQ hx4700 whose HTC ASIC3
> reportedly incorporates the Toshiba TC6380AF controller.
I wouldn't call this a "race."
> Towards the end of a multiple read (CMD18) operation the handler clears
> the final RXRDY status bit in the first loop iteration, sees the DATAEND
> status bit at the bottom of the loop, and so clears the DATAEND status
> bit in the second loop iteration. However the DATAEND interrupt is still
> queued in the system somewhere and can't be delivered until the handler
> has returned. This second interrupt is then reported as spurious in the
> next call to the handler. Likewise for single read (CMD17) operations.
> And something similar occurs for multiple write (CMD25) and single write
> (CMD24) operations, where CMDRESPEND and TXRQ status bits are cleared in
> a single call.
>
> In these cases the interrupt handler clears two separate interrupts when
> it should only clear the one interrupt for which it was invoked. The fix
> is to remove the while loop.
Sorry, don't understand. Isn't a spurious interrupt reported per "nobody
cared" if an ISR returns IRQ_NONE? And the TMIO ISR never does this. Is
the IRQ number, reported as spurious, that of TMIO? Is it shared?
> Signed-off-by: Paul Parsons <lost.distance@xxxxxxxxx>
> ---
>
> Interestingly a comment in tmio_mmc_pio.c regarding a problem on the
> SuperH concludes that "waiting for one more interrupt fixes the
> problem". Is that problem caused by the same race condition? And if so
> will this patch fix that too?
Don't think so, that comment only applies to the DMA case.
Thanks
Guennadi
>
> diff -uprN clean-2.6.39-rc7/drivers/mmc/host/tmio_mmc_pio.c linux-2.6.39-rc7/drivers/mmc/host/tmio_mmc_pio.c
> --- clean-2.6.39-rc7/drivers/mmc/host/tmio_mmc_pio.c 2011-05-11 00:54:17.651289833 +0100
> +++ linux-2.6.39-rc7/drivers/mmc/host/tmio_mmc_pio.c 2011-05-14 17:45:06.699829896 +0100
> @@ -593,58 +593,46 @@ static irqreturn_t tmio_mmc_irq(int irq,
> pr_debug_status(status);
> pr_debug_status(ireg);
>
> - if (!ireg) {
> - tmio_mmc_disable_mmc_irqs(host, status & ~irq_mask);
> -
> - pr_warning("tmio_mmc: Spurious irq, disabling! "
> - "0x%08x 0x%08x 0x%08x\n", status, irq_mask, ireg);
> - pr_debug_status(status);
> -
> + /* Card insert / remove attempts */
> + if (ireg & (TMIO_STAT_CARD_INSERT | TMIO_STAT_CARD_REMOVE)) {
> + tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_CARD_INSERT |
> + TMIO_STAT_CARD_REMOVE);
> + mmc_detect_change(host->mmc, msecs_to_jiffies(100));
> goto out;
> }
>
> - while (ireg) {
> - /* Card insert / remove attempts */
> - if (ireg & (TMIO_STAT_CARD_INSERT | TMIO_STAT_CARD_REMOVE)) {
> - tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_CARD_INSERT |
> - TMIO_STAT_CARD_REMOVE);
> - mmc_detect_change(host->mmc, msecs_to_jiffies(100));
> - }
> -
> - /* CRC and other errors */
> -/* if (ireg & TMIO_STAT_ERR_IRQ)
> - * handled |= tmio_error_irq(host, irq, stat);
> + /* CRC and other errors */
> +/* if (ireg & TMIO_STAT_ERR_IRQ)
> + * handled |= tmio_error_irq(host, irq, stat);
> */
>
> - /* Command completion */
> - if (ireg & (TMIO_STAT_CMDRESPEND | TMIO_STAT_CMDTIMEOUT)) {
> - tmio_mmc_ack_mmc_irqs(host,
> - TMIO_STAT_CMDRESPEND |
> - TMIO_STAT_CMDTIMEOUT);
> - tmio_mmc_cmd_irq(host, status);
> - }
> -
> - /* Data transfer */
> - if (ireg & (TMIO_STAT_RXRDY | TMIO_STAT_TXRQ)) {
> - tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_RXRDY | TMIO_STAT_TXRQ);
> - tmio_mmc_pio_irq(host);
> - }
> -
> - /* Data transfer completion */
> - if (ireg & TMIO_STAT_DATAEND) {
> - tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_DATAEND);
> - tmio_mmc_data_irq(host);
> - }
> -
> - /* Check status - keep going until we've handled it all */
> - status = sd_ctrl_read32(host, CTL_STATUS);
> - irq_mask = sd_ctrl_read32(host, CTL_IRQ_MASK);
> - ireg = status & TMIO_MASK_IRQ & ~irq_mask;
> + /* Command completion */
> + if (ireg & (TMIO_STAT_CMDRESPEND | TMIO_STAT_CMDTIMEOUT)) {
> + tmio_mmc_ack_mmc_irqs(host,
> + TMIO_STAT_CMDRESPEND |
> + TMIO_STAT_CMDTIMEOUT);
> + tmio_mmc_cmd_irq(host, status);
> + goto out;
> + }
> +
> + /* Data transfer */
> + if (ireg & (TMIO_STAT_RXRDY | TMIO_STAT_TXRQ)) {
> + tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_RXRDY | TMIO_STAT_TXRQ);
> + tmio_mmc_pio_irq(host);
> + goto out;
> + }
>
> - pr_debug("Status at end of loop: %08x\n", status);
> - pr_debug_status(status);
> + /* Data transfer completion */
> + if (ireg & TMIO_STAT_DATAEND) {
> + tmio_mmc_ack_mmc_irqs(host, TMIO_STAT_DATAEND);
> + tmio_mmc_data_irq(host);
> + goto out;
> }
> - pr_debug("MMC IRQ end\n");
> +
> + pr_warning("tmio_mmc: Spurious irq, disabling! "
> + "0x%08x 0x%08x 0x%08x\n", status, irq_mask, ireg);
> + pr_debug_status(status);
> + tmio_mmc_disable_mmc_irqs(host, status & ~irq_mask);
>
> out:
> return IRQ_HANDLED;
>
> --
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>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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