Re: [PATCH] serial: qcom-geni: Drop unsafe rx_buf realloc from setup_fifos()

[Praveen Talari <praveen.talari@oss.qualcomm.com>]

Hi

On 24-08-2026 18:26, Greg Kroah-Hartman wrote:
> On Mon, Aug 24, 2026 at 04:15:14PM +0530, Praveen Talari wrote:
>> The RX buffer is allocated once during probe using a fixed DMA_RX_BUF_SIZE
>> and is DMA-mapped for the lifetime of the port. However, setup_fifos()
>> attempts to reallocate rx_buf whenever the reported RX FIFO depth changes.
>> Since the DMA mapping is not re-established after reallocation, the buffer
>> pointer may change while the DMA engine continues using the stale DMA
>> address. This can result in RX DMA targeting memory that no longer
>> corresponds to the active buffer, leading to invalid DMA accesses and
>> potential memory corruption.
>>
>> The RX FIFO depth is unrelated to the size of rx_buf. The buffer is
>> allocated independently using DMA_RX_BUF_SIZE and all RX DMA paths consume
>> it at that fixed size. As such, resizing the buffer based on FIFO depth
>> changes provides no functional benefit.
>>
>> Signed-off-by: Praveen Talari <ptalari@qualcomm.com>
>> ---
>> Signed-off-by: Praveen Talari <praveen.talari@oss.qualcomm.com>
> Why is this signed-off-by twice, with different email addresses?

Apologies, that was a mistake while updating the commit message. Only 
praveen.talari@oss.qualcomm.com should be present for upstream 
submissions. I'll fix it in the next revision

Thanks,

Praveen Talari

>
> confused,
>
> greg k-h