On 27/08/18 11:24, Jisheng Zhang wrote:
> When using DMA, if the DMA addr spans 128MB boundary, we have to split
> the DMA transfer into two so that each one doesn't exceed the boundary.
>
> Signed-off-by: Jisheng Zhang <jisheng.zh...@synaptics.com>
> ---
> drivers/mmc/host/sdhci-of-dwcmshc.c | 41 +++++++++++++++++++++++++++++
> 1 file changed, 41 insertions(+)
>
> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c
> b/drivers/mmc/host/sdhci-of-dwcmshc.c
> index 1b7cd144fb01..cfbdae8703a1 100644
> --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
> +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
> @@ -8,21 +8,50 @@
> */
>
> #include <linux/clk.h>
> +#include <linux/mm.h>
> #include <linux/module.h>
> #include <linux/of.h>
> +#include <linux/sizes.h>
>
> #include "sdhci-pltfm.h"
>
> +#define BOUNDARY_OK(addr, len) \
> + ((addr | (SZ_128M - 1)) == ((addr + len - 1) | (SZ_128M - 1)))
> +
> struct dwcmshc_priv {
> struct clk *bus_clk;
> };
>
> +/*
> + * If DMA addr spans 128MB boundary, we split the DMA transfer into two
> + * so that each DMA transfer doesn't exceed the boundary.
> + */
> +static void dwcmshc_adma_write_desc(struct sdhci_host *host, void **desc,
> + dma_addr_t addr, int len, unsigned int cmd)
> +{
> + int tmplen, offset;
> +
> + if (likely(!len || BOUNDARY_OK(addr, len))) {
> + sdhci_adma_write_desc(host, desc, addr, len, cmd);
> + return;
> + }
> +
> + offset = addr & (SZ_128M - 1);
> + tmplen = SZ_128M - offset;
> + sdhci_adma_write_desc(host, desc, addr, tmplen, cmd);
> +
> + addr += tmplen;
> + len -= tmplen;
> + sdhci_adma_write_desc(host, desc, addr, len, cmd);
> +}
> +
> static const struct sdhci_ops sdhci_dwcmshc_ops = {
> .set_clock = sdhci_set_clock,
> .set_bus_width = sdhci_set_bus_width,
> .set_uhs_signaling = sdhci_set_uhs_signaling,
> .get_max_clock = sdhci_pltfm_clk_get_max_clock,
> .reset = sdhci_reset,
> + .adma_write_desc = dwcmshc_adma_write_desc,
> };
>
> static const struct sdhci_pltfm_data sdhci_dwcmshc_pdata = {
> @@ -36,12 +65,24 @@ static int dwcmshc_probe(struct platform_device *pdev)
> struct sdhci_host *host;
> struct dwcmshc_priv *priv;
> int err;
> + u32 extra;
>
> host = sdhci_pltfm_init(pdev, &sdhci_dwcmshc_pdata,
> sizeof(struct dwcmshc_priv));
> if (IS_ERR(host))
> return PTR_ERR(host);
>
> + /*
> + * The DMA table descriptor count is calculated as the maximum
> + * number of segments times 2, to allow for an alignment
> + * descriptor for each segment, plus 1 for a nop end descriptor,
> + * plus extra number for cross 128M boundary handling.
> + */
> + extra = DIV_ROUND_UP(totalram_pages, SZ_128M / PAGE_SIZE);
The amount of RAM is not necessarily the same as the highest physical
address. I think what you really want is max_pfn or max_possible_pfn
> + if (extra > SDHCI_MAX_SEGS)
> + extra = SDHCI_MAX_SEGS;
> + host->adma_table_cnt += extra;
> +
> pltfm_host = sdhci_priv(host);
> priv = sdhci_pltfm_priv(pltfm_host);
>
>
