linux-kernel - Re: [PATCH 1/2] mmc: mmci_sdmmc: fix DMA API warning overlapping mappings

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Date:   Thu, 28 May 2020 12:14:25 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Ludovic Barre <ludovic.barre@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Srini Kandagatla <srinivas.kandagatla@...aro.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH 1/2] mmc: mmci_sdmmc: fix DMA API warning overlapping mappings

On Tue, 26 May 2020 at 17:51, Ludovic Barre <ludovic.barre@...com> wrote:
>
> Turning on CONFIG_DMA_API_DEBUG_SG results in the following warning:
> WARNING: CPU: 1 PID: 20 at kernel/dma/debug.c:500 add_dma_entry+0x16c/0x17c
> DMA-API: exceeded 7 overlapping mappings of cacheline 0x031d2645
> Modules linked in:
> CPU: 1 PID: 20 Comm: kworker/1:1 Not tainted 5.5.0-rc2-00021-gdeda30999c2b-dirty #49
> Hardware name: STM32 (Device Tree Support)
> Workqueue: events_freezable mmc_rescan
> [<c03138c0>] (unwind_backtrace) from [<c030d760>] (show_stack+0x10/0x14)
> [<c030d760>] (show_stack) from [<c0f2eb28>] (dump_stack+0xc0/0xd4)
> [<c0f2eb28>] (dump_stack) from [<c034a14c>] (__warn+0xd0/0xf8)
> [<c034a14c>] (__warn) from [<c034a530>] (warn_slowpath_fmt+0x94/0xb8)
> [<c034a530>] (warn_slowpath_fmt) from [<c03bca0c>] (add_dma_entry+0x16c/0x17c)
> [<c03bca0c>] (add_dma_entry) from [<c03bdf54>] (debug_dma_map_sg+0xe4/0x3d4)
> [<c03bdf54>] (debug_dma_map_sg) from [<c0d09244>] (sdmmc_idma_prep_data+0x94/0xf8)
> [<c0d09244>] (sdmmc_idma_prep_data) from [<c0d05a2c>] (mmci_prep_data+0x2c/0xb0)
> [<c0d05a2c>] (mmci_prep_data) from [<c0d073ec>] (mmci_start_data+0x134/0x2f0)
> [<c0d073ec>] (mmci_start_data) from [<c0d078d0>] (mmci_request+0xe8/0x154)
> [<c0d078d0>] (mmci_request) from [<c0cecb44>] (mmc_start_request+0x94/0xbc)
>
> DMA api debug brings to light leaking dma-mappings, dma_map_sg and
> dma_unmap_sg are not correctly balanced.
>
> If a request is prepared, the dma_map/unmap are done in asynchronous
> call pre_req (prep_data) and post_req (unprep_data). In this case
> the dma-mapping is right balanced.
>
> But if the request was not prepared, the data->host_cookie is
> define to zero and the dma_map/unmap must be done in the request.
> The dma_map is called by mmci_dma_start (prep_data), but there is
> no dma_unmap in this case.
>
> This patch adds dma_unmap_sg when the dma is finalized and
> the data cookie is zero (request not prepared).
>
> Signed-off-by: Ludovic Barre <ludovic.barre@...com>

Applied for next by adding a fixes tag and a stable tag, thanks!

Fixes: 46b723dd867d ("mmc: mmci: add stm32 sdmmc variant")

Kind regards
Uffe


> ---
>  drivers/mmc/host/mmci_stm32_sdmmc.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
> index 14f99d8aa3f0..2965b1c062e1 100644
> --- a/drivers/mmc/host/mmci_stm32_sdmmc.c
> +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
> @@ -188,6 +188,9 @@ static int sdmmc_idma_start(struct mmci_host *host, unsigned int *datactrl)
>  static void sdmmc_idma_finalize(struct mmci_host *host, struct mmc_data *data)
>  {
>         writel_relaxed(0, host->base + MMCI_STM32_IDMACTRLR);
> +
> +       if (!data->host_cookie)
> +               sdmmc_idma_unprep_data(host, data, 0);
>  }
>
>  static void mmci_sdmmc_set_clkreg(struct mmci_host *host, unsigned int desired)
> --
> 2.17.1
>