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SubjectRe: [PATCH 2/2] mmc: mmci_sdmmc: fix DMA API warning max segment size
On Tue, 26 May 2020 at 17:51, Ludovic Barre <ludovic.barre@st.com> wrote:
>
> Turning on CONFIG_DMA_API_DEBUG_SG results in the following warning:
> WARNING: CPU: 1 PID: 85 at kernel/dma/debug.c:1302 debug_dma_map_sg+0x2a0/0x3cc
> mmci-pl18x 58005000.sdmmc: DMA-API: mapping sg segment longer than device claims to support [len=126976] [max=65536]
>
> dma api debug checks and compares the segment size to
> dma_get_max_seg_size (dev->dma_parms->max_segment_size),
> the sdmmc variant has an internal DMA and should define
> its max_segment_size constraint to avoid this warning.
>
> This Patch defines the dev->dma_parms->max_segment_size
> with the constraint already set for mmc core
> (host->mmc->max_seg_size).
>
> Signed-off-by: Ludovic Barre <ludovic.barre@st.com>

Applied for next, thanks!

Note, a manual backport is needed for stable, as
dma_set_max_seg_size() will fail for older kernels.
We needed to revert 9495b7e92f7 ("driver core: platform: Initialize
dma_parms for platform devices"), for stable kernels [1].

Kind regards
Uffe

[1]
https://lkml.org/lkml/2020/5/26/1216


> ---
> drivers/mmc/host/mmci_stm32_sdmmc.c | 11 +++++------
> 1 file changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/host/mmci_stm32_sdmmc.c b/drivers/mmc/host/mmci_stm32_sdmmc.c
> index 2965b1c062e1..51db30acf4dc 100644
> --- a/drivers/mmc/host/mmci_stm32_sdmmc.c
> +++ b/drivers/mmc/host/mmci_stm32_sdmmc.c
> @@ -119,20 +119,19 @@ static void sdmmc_idma_unprep_data(struct mmci_host *host,
> static int sdmmc_idma_setup(struct mmci_host *host)
> {
> struct sdmmc_idma *idma;
> + struct device *dev = mmc_dev(host->mmc);
>
> - idma = devm_kzalloc(mmc_dev(host->mmc), sizeof(*idma), GFP_KERNEL);
> + idma = devm_kzalloc(dev, sizeof(*idma), GFP_KERNEL);
> if (!idma)
> return -ENOMEM;
>
> host->dma_priv = idma;
>
> if (host->variant->dma_lli) {
> - idma->sg_cpu = dmam_alloc_coherent(mmc_dev(host->mmc),
> - SDMMC_LLI_BUF_LEN,
> + idma->sg_cpu = dmam_alloc_coherent(dev, SDMMC_LLI_BUF_LEN,
> &idma->sg_dma, GFP_KERNEL);
> if (!idma->sg_cpu) {
> - dev_err(mmc_dev(host->mmc),
> - "Failed to alloc IDMA descriptor\n");
> + dev_err(dev, "Failed to alloc IDMA descriptor\n");
> return -ENOMEM;
> }
> host->mmc->max_segs = SDMMC_LLI_BUF_LEN /
> @@ -143,7 +142,7 @@ static int sdmmc_idma_setup(struct mmci_host *host)
> host->mmc->max_seg_size = host->mmc->max_req_size;
> }
>
> - return 0;
> + return dma_set_max_seg_size(dev, host->mmc->max_seg_size);
> }
>
> static int sdmmc_idma_start(struct mmci_host *host, unsigned int *datactrl)
> --
> 2.17.1
>

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