mmc: moxart-mmc: Use sg_miter for PIO

Use the scatterlist memory iterator instead of just
dereferencing virtual memory using sg_virt().
This make highmem references work properly.

Suggested-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/linux-mmc/20240122073423.GA25859@lst.de/
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240127-mmc-proper-kmap-v2-4-d8e732aa97d1@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
index 8ede4ce..b88d6de 100644 (file)
--- a/drivers/mmc/host/moxart-mmc.c
+++ b/drivers/mmc/host/moxart-mmc.c
@@ -131,12 +131,10 @@ struct moxart_host {
        struct dma_async_tx_descriptor  *tx_desc;
        struct mmc_host                 *mmc;
        struct mmc_request              *mrq;
-       struct scatterlist              *cur_sg;
        struct completion               dma_complete;
        struct completion               pio_complete;
 
-       u32                             num_sg;
-       u32                             data_remain;
+       struct sg_mapping_iter          sg_miter;
        u32                             data_len;
        u32                             fifo_width;
        u32                             timeout;
@@ -148,35 +146,6 @@ struct moxart_host {
        bool                            is_removed;
 };
 
-static inline void moxart_init_sg(struct moxart_host *host,
-                                 struct mmc_data *data)
-{
-       host->cur_sg = data->sg;
-       host->num_sg = data->sg_len;
-       host->data_remain = host->cur_sg->length;
-
-       if (host->data_remain > host->data_len)
-               host->data_remain = host->data_len;
-}
-
-static inline int moxart_next_sg(struct moxart_host *host)
-{
-       int remain;
-       struct mmc_data *data = host->mrq->cmd->data;
-
-       host->cur_sg++;
-       host->num_sg--;
-
-       if (host->num_sg > 0) {
-               host->data_remain = host->cur_sg->length;
-               remain = host->data_len - data->bytes_xfered;
-               if (remain > 0 && remain < host->data_remain)
-                       host->data_remain = remain;
-       }
-
-       return host->num_sg;
-}
-
 static int moxart_wait_for_status(struct moxart_host *host,
                                  u32 mask, u32 *status)
 {
@@ -309,14 +278,28 @@ static void moxart_transfer_dma(struct mmc_data *data, struct moxart_host *host)
 
 static void moxart_transfer_pio(struct moxart_host *host)
 {
+       struct sg_mapping_iter *sgm = &host->sg_miter;
        struct mmc_data *data = host->mrq->cmd->data;
        u32 *sgp, len = 0, remain, status;
 
        if (host->data_len == data->bytes_xfered)
                return;
 
-       sgp = sg_virt(host->cur_sg);
-       remain = host->data_remain;
+       /*
+        * By updating sgm->consumes this will get a proper pointer into the
+        * buffer at any time.
+        */
+       if (!sg_miter_next(sgm)) {
+               /* This shold not happen */
+               dev_err(mmc_dev(host->mmc), "ran out of scatterlist prematurely\n");
+               data->error = -EINVAL;
+               complete(&host->pio_complete);
+               return;
+       }
+       sgp = sgm->addr;
+       remain = sgm->length;
+       if (remain > host->data_len)
+               remain = host->data_len;
 
        if (data->flags & MMC_DATA_WRITE) {
                while (remain > 0) {
@@ -331,6 +314,7 @@ static void moxart_transfer_pio(struct moxart_host *host)
                                sgp++;
                                len += 4;
                        }
+                       sgm->consumed += len;
                        remain -= len;
                }
 
@@ -347,22 +331,22 @@ static void moxart_transfer_pio(struct moxart_host *host)
                                sgp++;
                                len += 4;
                        }
+                       sgm->consumed += len;
                        remain -= len;
                }
        }
 
-       data->bytes_xfered += host->data_remain - remain;
-       host->data_remain = remain;
-
-       if (host->data_len != data->bytes_xfered)
-               moxart_next_sg(host);
-       else
+       data->bytes_xfered += sgm->consumed;
+       if (host->data_len == data->bytes_xfered) {
                complete(&host->pio_complete);
+               return;
+       }
 }
 
 static void moxart_prepare_data(struct moxart_host *host)
 {
        struct mmc_data *data = host->mrq->cmd->data;
+       unsigned int flags = SG_MITER_ATOMIC; /* Used from IRQ */
        u32 datactrl;
        int blksz_bits;
 
@@ -373,15 +357,19 @@ static void moxart_prepare_data(struct moxart_host *host)
        blksz_bits = ffs(data->blksz) - 1;
        BUG_ON(1 << blksz_bits != data->blksz);
 
-       moxart_init_sg(host, data);
-
        datactrl = DCR_DATA_EN | (blksz_bits & DCR_BLK_SIZE);
 
-       if (data->flags & MMC_DATA_WRITE)
+       if (data->flags & MMC_DATA_WRITE) {
+               flags |= SG_MITER_FROM_SG;
                datactrl |= DCR_DATA_WRITE;
+       } else {
+               flags |= SG_MITER_TO_SG;
+       }
 
        if (moxart_use_dma(host))
                datactrl |= DCR_DMA_EN;
+       else
+               sg_miter_start(&host->sg_miter, data->sg, data->sg_len, flags);
 
        writel(DCR_DATA_FIFO_RESET, host->base + REG_DATA_CONTROL);
        writel(MASK_DATA | FIFO_URUN | FIFO_ORUN, host->base + REG_CLEAR);
@@ -454,6 +442,9 @@ static void moxart_request(struct mmc_host *mmc, struct mmc_request *mrq)
        }
 
 request_done:
+       if (!moxart_use_dma(host))
+               sg_miter_stop(&host->sg_miter);
+
        spin_unlock_irqrestore(&host->lock, flags);
        mmc_request_done(host->mmc, mrq);
 }