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From:   Mathieu Malaterre <malat@debian.org>
Date:   Wed, 17 Oct 2018 15:38:07 +0200
Message-ID: <CA+7wUszkduiKMVx5Et3Q2-2tz72CXUKE1_kndC6V1d45uEY2Aw@mail.gmail.com>
Subject: Re: Bug report: MIPS CI20/jz4740-mmc DMA and PREEMPT_NONE
To:     aaro.koskinen@iki.fi
Cc:     Linux-MIPS <linux-mips@linux-mips.org>, linux-mmc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Ezequiel Garcia <ezequiel@collabora.co.uk>
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Hi,

On Sun, Oct 14, 2018 at 7:04 PM Aaro Koskinen <aaro.koskinen@iki.fi> wrote:
>
> Hi,
>
> There is something wrong with jz4740-mmc in current mainline kernel
> (tested v4.18 and 4.19-rc, the MMC support for CI20 does not exist
> prior those), as the DMA support does not work properly if I disable
> kernel pre-emption. The console gets flooded with:
>
> [   16.461094] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 567 host->next_data.cookie 568
> [   16.473120] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 568 host->next_data.cookie 569
> [   16.485144] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 569 host->next_data.cookie 570
> [   16.497170] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 570 host->next_data.cookie 571
> [   16.509194] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 571 host->next_data.cookie 572
> [   16.532421] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 572 host->next_data.cookie 573
> [   16.544594] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 573 host->next_data.cookie 574
> [   16.556621] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 574 host->next_data.cookie 575
> [   16.568638] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 575 host->next_data.cookie 576
> [   16.601092] jz4740-mmc 13450000.mmc: [jz4740_mmc_prepare_dma_data] invalid cookie: data->host_cookie 582 host->next_data.cookie 583
>
> etc. ad inf.
>
> This should be easily reproducible on CI20 board with ci20_defconfig
> and setting CONFIG_PREEMPT_NONE=y.

Since CONFIG_PREEMPT has been 'y' since at least commit 0752f92934292
could you confirm that the original mmc driver (kernel from imgtech
people) did work ok with PREEMPT_NONE (sorry I did not do my homework)
?

Thanks

> A.