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mmc: sdhci: allow drivers to pre-allocate bounce buffer

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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 <adrian.hunter@intel.com>
Signed-off-by: Albert Yang <yangzh0906@thundersoft.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Albert Yang 2026-01-23 17:53:38 +08:00 committed by Ulf Hansson
parent d515962316
commit ef7eb1a709
1 changed files with 7 additions and 0 deletions
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7
drivers/mmc/host/sdhci.c
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@ -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;