From ef7eb1a7094dbb5042ea1bed34193c1415fb9844 Mon Sep 17 00:00:00 2001 From: Albert Yang Date: Fri, 23 Jan 2026 17:53:38 +0800 Subject: [PATCH] mmc: sdhci: allow drivers to pre-allocate bounce buffer Allow platform drivers to pre-allocate bounce buffer by checking if host->bounce_buffer is already set before attempting allocation. This enables platforms with specific DMA constraints (such as 32-bit DMA on controllers that cannot access high memory) to use their own reserved memory regions for the bounce buffer. Suggested-by: Adrian Hunter Signed-off-by: Albert Yang Acked-by: Adrian Hunter Signed-off-by: Ulf Hansson --- drivers/mmc/host/sdhci.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c index 1ff15fa9b042..b1a3cd574c84 100644 --- a/drivers/mmc/host/sdhci.c +++ b/drivers/mmc/host/sdhci.c @@ -4193,6 +4193,12 @@ static void sdhci_allocate_bounce_buffer(struct sdhci_host *host) unsigned int bounce_size; int ret; + /* Drivers may have already allocated the buffer */ + if (host->bounce_buffer) { + bounce_size = host->bounce_buffer_size; + max_blocks = bounce_size / 512; + goto out; + } /* * Cap the bounce buffer at 64KB. Using a bigger bounce buffer * has diminishing returns, this is probably because SD/MMC @@ -4241,6 +4247,7 @@ static void sdhci_allocate_bounce_buffer(struct sdhci_host *host) host->bounce_buffer_size = bounce_size; +out: /* Lie about this since we're bouncing */ mmc->max_segs = max_blocks; mmc->max_seg_size = bounce_size;