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spi: atmel_qspi: fix race condition in transfer completion check

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In atmel_qspi_transfer(), the status register is polled with:

  imr = QSPI_SR_INSTRE | QSPI_SR_CSR;
  return readl_poll_timeout(aq->regs + QSPI_SR, sr,
                            (sr & imr) == imr,
                            ATMEL_QSPI_TIMEOUT);

However, this is racy: QSPI_SR_INSTRE can be set before QSPI_SR_CSR,
and will then be cleared by the read. If that happens, the condition
"(sr & imr) == imr" can never be true, and the function times out.

This race condition is avoided in at91bootstrap by accumulating the
status bits across reads until both bits have been observed:

  /* Poll INSTruction End and Chip Select Rise flags. */
  imr = (QSPI_SR_INSTRE | QSPI_SR_CSR);
  sr = 0;
  do {
    udelay(1);
    sr |= qspi_readl(qspi, QSPI_SR) & imr;
  } while ((--timeout) && (sr != imr));

Update U-Boot's atmel_qspi_transfer() to use the same pattern,
ensuring that both flags are observed even if they are not set
simultaneously.

Signed-off-by: Ramin Moussavi <lordrasmus@gmail.com>
[eugen.hristev@linaro.org: remove 'sr' and fix commit msg]
Signed-off-by: Eugen Hristev <eugen.hristev@linaro.org>
This commit is contained in:
Ramin Moussavi
2025-07-22 20:27:09 +02:00
committed by Eugen Hristev
parent a8f20bb665
commit 709b5be0a4
1 changed files with 12 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/spi/atmel-quadspi.c
View File

@@ -615,7 +615,8 @@ static int atmel_qspi_set_cfg(struct atmel_qspi *aq,
static int atmel_qspi_transfer(struct atmel_qspi *aq,
const struct spi_mem_op *op, u32 offset)
{
u32 sr, imr;
u32 imr, val = 0;
unsigned long timeout;
/* Skip to the final steps if there is no data */
if (op->data.nbytes) {
@@ -636,8 +637,16 @@ static int atmel_qspi_transfer(struct atmel_qspi *aq,
/* Poll INSTruction End and Chip Select Rise flags. */
imr = QSPI_SR_INSTRE | QSPI_SR_CSR;
return readl_poll_timeout(aq->regs + QSPI_SR, sr, (sr & imr) == imr,
ATMEL_QSPI_TIMEOUT);
timeout = timer_get_us() + ATMEL_QSPI_TIMEOUT;
while (1) {
val |= readl(aq->regs + QSPI_SR) & imr;
if ((val & imr) == imr)
return 0;
if (time_after(timer_get_us(), timeout))
return -ETIMEDOUT;
}
}
static int atmel_qspi_sama7g5_set_cfg(struct atmel_qspi *aq,