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Subject[PATCH] mmc: sunxi-mmc: Correct the maximum segment size
Date
According to the DMA descriptor documentation, the lowest two bits of
the size field are ignored, so the size must be rounded up to a multiple
of 4 bytes. Furthermore, 0 is not a valid buffer size; setting the size
to 0 will cause that DMA descriptor to be ignored.

Together, these restrictions limit the maximum DMA segment size to 4
less than the power-of-two width of the size field.

Fixes: 3cbcb16095f9 ("mmc: sunxi: Add driver for SD/MMC hosts found on Allwinner sunxi SoCs")
Signed-off-by: Samuel Holland <samuel@sholland.org>
---

drivers/mmc/host/sunxi-mmc.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/host/sunxi-mmc.c b/drivers/mmc/host/sunxi-mmc.c
index c62afd212692..4bd5f37b1036 100644
--- a/drivers/mmc/host/sunxi-mmc.c
+++ b/drivers/mmc/host/sunxi-mmc.c
@@ -214,6 +214,9 @@
#define SDXC_IDMAC_DES0_CES BIT(30) /* card error summary */
#define SDXC_IDMAC_DES0_OWN BIT(31) /* 1-idma owns it, 0-host owns it */

+/* Buffer size must be a multiple of 4 bytes. */
+#define SDXC_IDMAC_SIZE_ALIGN 4
+
#define SDXC_CLK_400K 0
#define SDXC_CLK_25M 1
#define SDXC_CLK_50M 2
@@ -361,17 +364,15 @@ static void sunxi_mmc_init_idma_des(struct sunxi_mmc_host *host,
{
struct sunxi_idma_des *pdes = (struct sunxi_idma_des *)host->sg_cpu;
dma_addr_t next_desc = host->sg_dma;
- int i, max_len = (1 << host->cfg->idma_des_size_bits);
+ int i;

for (i = 0; i < data->sg_len; i++) {
pdes[i].config = cpu_to_le32(SDXC_IDMAC_DES0_CH |
SDXC_IDMAC_DES0_OWN |
SDXC_IDMAC_DES0_DIC);

- if (data->sg[i].length == max_len)
- pdes[i].buf_size = 0; /* 0 == max_len */
- else
- pdes[i].buf_size = cpu_to_le32(data->sg[i].length);
+ pdes[i].buf_size = cpu_to_le32(ALIGN(data->sg[i].length,
+ SDXC_IDMAC_SIZE_ALIGN));

next_desc += sizeof(struct sunxi_idma_des);
pdes[i].buf_addr_ptr1 =
@@ -1420,7 +1421,8 @@ static int sunxi_mmc_probe(struct platform_device *pdev)
mmc->max_blk_count = 8192;
mmc->max_blk_size = 4096;
mmc->max_segs = PAGE_SIZE / sizeof(struct sunxi_idma_des);
- mmc->max_seg_size = (1 << host->cfg->idma_des_size_bits);
+ mmc->max_seg_size = (1 << host->cfg->idma_des_size_bits) -
+ SDXC_IDMAC_SIZE_ALIGN;
mmc->max_req_size = mmc->max_seg_size * mmc->max_segs;
/* 400kHz ~ 52MHz */
mmc->f_min = 400000;
--
2.35.1
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