On 26/01/16 15:39, Russell King wrote:
> Allocate both the alignment and DMA descriptor buffers together. The
> size of the alignment buffer will always be aligned to the hosts
> required alignment, which gives appropriate alignment to the DMA
> descriptors.
>
> We have a maximum of 128 segments, and a maximum alignment of 64 bits.
> This gives a maximum alignment buffer size of 1024 bytes.
>
> The DMA descriptors are a maximum of 12 bytes, and we allocate 128 * 2
> + 1 of these, which gives a maximum DMA descriptor buffer size of 3084
> bytes.
>
> This means the allocation for a 4K page sized system will be an order-1
> allocation, since the resulting overall size is 4108. This is more
> prone to failure than page-sized allocations, but since this allocation
> commonly occurs at startup, the chances of failure are small.
>
> Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
> ---
> drivers/mmc/host/sdhci.c | 55 +++++++++++++++++-------------------------------
> 1 file changed, 19 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index c70a2d2eb6d9..f23fdb485393 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2932,6 +2932,9 @@ int sdhci_add_host(struct sdhci_host *host)
> host->flags &= ~SDHCI_USE_SDMA;
>
> if (host->flags & SDHCI_USE_ADMA) {
> + dma_addr_t dma;
> + void *buf;
> +
> /*
> * The DMA descriptor table size is calculated as the maximum
> * number of segments times 2, to allow for an alignment
> @@ -2947,45 +2950,27 @@ int sdhci_add_host(struct sdhci_host *host)
> SDHCI_ADMA2_32_DESC_SZ;
> host->desc_sz = SDHCI_ADMA2_32_DESC_SZ;
> }
> - host->adma_table = dma_alloc_coherent(mmc_dev(mmc),
> - host->adma_table_sz,
> - &host->adma_addr,
> - GFP_KERNEL);
> +
> host->align_buffer_sz = SDHCI_MAX_SEGS * SDHCI_ADMA2_ALIGN;
> - host->align_buffer = dma_alloc_coherent(mmc_dev(mmc),
> - host->align_buffer_sz,
> - &host->align_addr,
> - GFP_KERNEL);
> - if (!host->adma_table || !host->align_buffer) {
> - if (host->adma_table)
> - dma_free_coherent(mmc_dev(mmc),
> - host->adma_table_sz,
> - host->adma_table,
> - host->adma_addr);
> - if (host->align_buffer)
> - dma_free_coherent(mmc_dev(mmc),
> - host->align_buffer_sz,
> - host->align_buffer,
> - host->align_addr);
> + buf = dma_alloc_coherent(mmc_dev(mmc), host->align_buffer_sz +
> + host->adma_table_sz, &dma, GFP_KERNEL);
> + if (!buf) {
> pr_warn("%s: Unable to allocate ADMA buffers - falling back to standard DMA\n",
> mmc_hostname(mmc));
> host->flags &= ~SDHCI_USE_ADMA;
> - host->adma_table = NULL;
> - host->align_buffer = NULL;
> - } else if (host->adma_addr & (SDHCI_ADMA2_DESC_ALIGN - 1)) {
> + } else if (dma & SDHCI_ADMA2_MASK) {
The descriptor table has a bigger alignment requirement, so that should remain the check i.e.
} else if ((dma + host->align_buffer_sz) & (SDHCI_ADMA2_DESC_ALIGN - 1)) {
> pr_warn("%s: unable to allocate aligned ADMA descriptor\n",
> mmc_hostname(mmc));
> host->flags &= ~SDHCI_USE_ADMA;
> - dma_free_coherent(mmc_dev(mmc), host->adma_table_sz,
> - host->adma_table, host->adma_addr);
> - dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz,
> - host->align_buffer, host->align_addr);
> - host->adma_table = NULL;
> - host->align_buffer = NULL;
> - }
> + dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz +
> + host->adma_table_sz, buf, dma);
> + } else {
> + host->align_buffer = buf;
> + host->align_addr = dma;
>
> - /* dma_alloc_coherent returns page aligned and sized buffers */
> - BUG_ON(host->align_addr & SDHCI_ADMA2_MASK);
> + host->adma_table = buf + host->align_buffer_sz;
> + host->adma_addr = dma + host->align_buffer_sz;
> + }
> }
>
> /*
> @@ -3446,12 +3431,10 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
> if (!IS_ERR(mmc->supply.vqmmc))
> regulator_disable(mmc->supply.vqmmc);
>
> - if (host->adma_table)
> - dma_free_coherent(mmc_dev(mmc), host->adma_table_sz,
> - host->adma_table, host->adma_addr);
> if (host->align_buffer)
> - dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz,
> - host->align_buffer, host->align_addr);
> + dma_free_coherent(mmc_dev(mmc), host->align_buffer_sz +
> + host->adma_table_sz, host->align_buffer,
> + host->align_addr);
>
> host->adma_table = NULL;
> host->align_buffer = NULL;
>
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